METHODS: ECs were exposed to orbital shear stress with an orbital shaker (210 rpm) or laminar shear stress (14 dyne/cm 2) with a parallel plate. Shear stress in the orbital shaker was measured with optical velocimetry. Cell proliferation was assessed with direct counting and proliferating cell nuclear antigen staining; apoptosis was assessed with transferase-mediated deoxyuridine triphosphate nick end labeling staining. Cell surface E-selectin and intercellular adhesion molecule expression were assessed with fluorescence-activated cell sorting. Akt phosphorylation was assessed with Western blotting.

RESULTS: Orbital shear stress increased EC proliferation by 29% and 3 [H]thymidine incorporation two-fold compared to 16% and 38% decreases, respectively, in ECs treated with laminar shear stress (P < .0001 and P = .03, analysis of variance). Cells in the periphery of the culture well aligned to the direction of shear stress similar to the shape change seen with laminar shear stress, whereas ECs in the center of the well appeared unaligned similar to ECs not exposed to shear stress. Shear stress at the bottom surface of the culture well was reduced in the center of the well (5 dyne/cm 2) compared to the periphery (11 dyne/cm 2); the Reynolds' number was 2066. ECs were seeded differentially in the center and periphery of the wells. ECs in the center of the well had increased proliferation, increased apoptosis, reduced Akt phosphorylation, increased intercelluar adhesion molecule expression, and reduced E-selectin down-regulation, compared with ECs in the periphery of the well.

CONCLUSION: Although the orbital shaker does not apply uniform shear stress throughout the culture well, arterial magnitudes of shear stress are present in the periphery of the well. ECs cultured in the center of the well exposed to low magnitudes of orbital shear stress might be a model of the "activated" EC phenotype.

CLINICAL RELEVANCE: The perfect in vitro model to study and assess treatments for atherosclerosis and neointimal hyperplasia does not exists. An extensive body of literature describing effects of laminar shear stress on endothelial cells has contributed to our understanding of the interactions between shear stress and blood vessels. Laminar shear stress is atheroprotective, whereas oscillatory or disturbed shear stress correlates with areas of atherosclerosis and neointimal hyperplasia in vivo. This study describes the orbital shear stress model, its effects on endothelial cell proliferation and apoptosis, and suggests that activation of the intracellular Akt pathway is associated with these differing effects of laminar and orbital shear stress on endothelial cells.}, } @article {pmid14979546, year = {2004}, author = {Martínez, SA and Rodríguez, MG and Aguilar, R and Soto, G}, title = {Removal of chromium hexavalent from rinsing chromating waters electrochemical reduction in a laboratory pilot plant.}, journal = {Water science and technology : a journal of the International Association on Water Pollution Research}, volume = {49}, number = {1}, pages = {115-122}, pmid = {14979546}, issn = {0273-1223}, mesh = {Carcinogens, Environmental/chemistry/*isolation & purification ; Chromium/chemistry/*isolation & purification ; Electrochemistry ; Kinetics ; *Models, Theoretical ; Oxidation-Reduction ; Water Pollutants/*isolation & purification ; Water Purification/methods ; }, abstract = {In this work, experiments in a 16 L operating volume laboratory pilot plant with ring iron rotary electrodes were performed, obtaining an overall kinetic equation rate of hexavalent chromium reduction concentration and current density-dependent. Other scale-up criteria such as Reynolds' number were also evaluated to ensure a completely stirred reactor at low energy expenditure. A dimensionless N(E) is a relationship between liquid properties and the electric charge supplied to the system. The number, which depends on the rotation iron ring electrode speed number and the current density, is proposed to be used as scale-up criterion. It was found that at N(Re) = 42,179 (130 rpm rotation electrodes rate) and at N(E) = 9.8 x 10(5) (current density of 113 A/m2), complete mixing was reached at minimum energy spent and the process becomes more efficient. In addition, it was found that the higher the current density, the less treatment time and less energy spent on agitation. After the electrochemical treatment the Cr(VI) concentration in the rinsing wastewater was less than 0.5 mg/L.}, } @article {pmid10593472, year = {1999}, author = {Rueckoldt, H and Vangerow, B and Marx, G and Haubitz, B and Meyer, MC and Piepenbrock, S and Leuwer, M}, title = {Xenon inhalation increases airway pressure in ventilated patients.}, journal = {Acta anaesthesiologica Scandinavica}, volume = {43}, number = {10}, pages = {1060-1064}, doi = {10.1034/j.1399-6576.1999.431016.x}, pmid = {10593472}, issn = {0001-5172}, mesh = {Administration, Inhalation ; Adolescent ; Adult ; Aged ; Aged, 80 and over ; Airway Resistance/*drug effects ; Blood Pressure/drug effects ; Carbon Dioxide/blood ; Cerebrovascular Circulation ; Female ; Heart Rate/drug effects ; Humans ; Male ; Middle Aged ; Oxygen/blood ; *Respiration, Artificial ; Retrospective Studies ; Tomography, X-Ray Computed ; Xenon/administration & dosage/*pharmacology ; }, abstract = {BACKGROUND: The inert gas xenon, known as an anaesthetic for nearly 50 years, is also used as a contrast agent during computerised tomography (CT)-scanning. As xenon has a higher density and viscosity than air, xenon inhalation may increase airway resistance.

METHODS: In a retrospective study we investigated the effects of 33% xenon/67% oxygen on airway pressure and cardio-respiratory parameters in 37 long-term mechanically ventilated patients undergoing cerebral blood flow (rCBF) measurements by means of stable xenon-enhanced CT.

RESULTS: Xenon administration caused a significant increase in peak airway pressure from 31.6+/-8.0 cm H2O to 42.7+/-16.9 cm H2O. This effect was reproducible, did not occur after reduction of inspiratory flow rate by 50% from 0.56+/-0.15 L x s(-1) to 0.28+/-0.08 L x s(-1), and vanished immediately after termination of xenon delivery.

CONCLUSION: Due to the higher density and viscosity of this gas mixture, ventilation with xenon/oxygen produces a higher Reynolds' number than oxygen/air when given at the same flow rate. This means that during xenon ventilation the zone of transition from turbulent to laminar gas flow may be located more peripherally (in smaller airways) than during oxygen/air ventilation with a subsequent increase in airway resistance. Our results indicate that xenon inhalation may cause a clinically relevant increase of peak airway pressure in mechanically ventilated patients.}, } @article {pmid10517207, year = {1999}, author = {Pedersen, EM and Kim, WY and Staalsen, NH and Hasenkam, JM and Nygaard, H and Paulsen, PK}, title = {Development of velocity profiles and retrograde flow in the porcine abdominal aorta under different haemodynamic conditions.}, journal = {Scandinavian cardiovascular journal : SCJ}, volume = {33}, number = {4}, pages = {206-214}, doi = {10.1080/14017439950141632}, pmid = {10517207}, issn = {1401-7431}, mesh = {Animals ; Aorta, Abdominal/anatomy & histology/diagnostic imaging/*physiology ; Blood Flow Velocity/*physiology ; Cardiac Pacing, Artificial ; Electrocardiography ; Heart Rate ; Hemodynamics/*physiology ; Signal Processing, Computer-Assisted ; Swine ; Ultrasonography, Doppler, Pulsed ; }, abstract = {Low and/or oscillating wall shear stresses are related to the development of atherosclerosis and this oscillation is influenced by changes in basic haemodynamics (exercise). The objective of this study was to provide in vivo data on the development of velocity profiles and oscillating blood velocities in the abdominal aorta under varying haemodynamic conditions. Six anaesthetized, 90-kg pigs were used in the study. Abdominal aortic velocity profiles across the anterior-posterior diameter were acquired at different axial positions using 10 MHz pulsed Doppler ultrasound. Measurements were obtained under normal conditions and during cardiac pacing up to 170 beats/min. Velocity profiles were obtained during heart rates ranging between 58 and 169 beats/min, and during flow rates ranging between 0.57 and 2.89 l/min. Main outcome measures included minimum velocities, frequency index, shape of velocity profiles (velocity distribution index), Reynolds' numbers, and Womersley's frequency parameter. Velocity profiles were blunted, with lowest velocities at the distal posterior vessel wall. Multiple regression analysis showed the development of velocity profiles to be inversely correlated with the pulsatility index, Womersley's frequency parameter and the mean Reynolds' number (r = 0.89, p < 0.0005). Minimum velocities were negatively correlated with the PI, Womersley's frequency parameter and positively with the mean Reynolds' number (r = 0.94, p < 10(-8)). Retrograde velocities (and hence oscillating wall shear stresses) were present at mean Reynolds' number < 1000. The oscillation of blood velocities at the wall in the porcine abdominal aorta was highly dependent on general haemodynamics (i.e. flow, heart rate and vessel diameter as expressed in the Reynolds' numbers and Womersley's frequency parameters). The velocity profiles in the abdominal aorta were found to be far from parabolic. These findings have important implications for the understanding and future modelling of the complex haemodynamics in the abdominal aorta and their relation to the development of atherosclerotic disease.}, } @article {pmid8248974, year = {1993}, author = {Fleischer, LH and Young, WL and Pile-Spellman, J and terPenning, B and Kader, A and Stein, BM and Mohr, JP}, title = {Relationship of transcranial Doppler flow velocities and arteriovenous malformation feeding artery pressures.}, journal = {Stroke}, volume = {24}, number = {12}, pages = {1897-1902}, doi = {10.1161/01.str.24.12.1897}, pmid = {8248974}, issn = {0039-2499}, support = {R01-27713//PHS HHS/United States ; }, mesh = {Adult ; Blood Pressure ; Cerebral Hemorrhage/prevention & control ; Female ; Humans ; Intracranial Arteriovenous Malformations/*physiopathology ; Male ; Regional Blood Flow ; Ultrasonics ; }, abstract = {BACKGROUND AND PURPOSE: Feeding mean arterial pressure immediately proximal to the nidus of arteriovenous malformations may influence the frequency of spontaneous intracerebral hemorrhage. This study assessed the usefulness of transcranial Doppler ultrasound velocities as a noninvasive estimate of feeding mean arterial pressure.

METHODS: We studied 41 patients undergoing 73 staged treatments of arteriovenous malformations with endovascular embolization, surgery, or both. Before treatment during the awake state, transcranial Doppler mean and peak velocities were recorded in proximal Willisian vessels. During superselective angiography with the patient under conscious sedation or during surgery with the patient under general anesthesia, feeding mean arterial pressure was measured through a 1.5F transfemoral intracranial microcatheter or a 26-g needle by direct puncture. Measurement of insonated artery diameter was possible in 41 embolizations, and a flow velocity index (mL/min) and Reynolds' number were estimated.

RESULTS: Mean +/- SEM feeding mean arterial pressure was 38 +/- 2 mm Hg at a systemic mean arterial pressure of 77 +/- 2 mm Hg; mean velocity was 102 +/- 4 cm/s. There was an inverse correlation between feeding mean arterial pressure and parent artery mean velocity (y = -0.74x + 130, r = .35, P = .0025). The best correlation was for the first treatment in each patient (n = 27) using the highest peak velocity obtainable in a Willisian vessel ipsilateral to the arteriovenous malformation (y = -1.61x + 221, r = .62, P = .0005). Flow velocity index (775 +/- 106 mL/min) did not correlate with feeding mean arterial pressure, but there was a weak correlation with Reynolds' number (y = -12x + 1616, r = .27, P = .1283). Mean Reynolds' number was 1257 +/- 119.

CONCLUSIONS: Transcranial Doppler mean velocity is correlated with feeding mean arterial pressure but only weakly predictive. Considerations influencing the relation of distal feeding mean arterial pressure to proximal mean velocity might include the influence of other fistulae in the circuit between major inflow and outflow channels as well as turbulent flow at vascular branch points between point of insonation and the nidus, as suggested by Reynolds' number values of more than 400.}, } @article {pmid1576123, year = {1992}, author = {Yamamoto, T and Tanaka, H and Jones, CJ and Lever, MJ and Parker, KH and Kimura, A and Hiramatsu, O and Ogasawara, Y and Tsujioka, K and Caro, CC}, title = {Blood velocity profiles in the origin of the canine renal artery and their relevance in the localization and development of atherosclerosis.}, journal = {Arteriosclerosis and thrombosis : a journal of vascular biology}, volume = {12}, number = {5}, pages = {626-632}, doi = {10.1161/01.atv.12.5.626}, pmid = {1576123}, issn = {1049-8834}, mesh = {Animals ; Aorta/diagnostic imaging ; Arteriosclerosis/*etiology/pathology ; *Blood Flow Velocity ; Dogs ; Female ; Male ; Renal Artery/diagnostic imaging/*physiology ; Ultrasonography ; }, abstract = {Using a 20-MHz 80-channel pulsed Doppler velocimeter and 30-MHz high-resolution echo ultrasound, we investigated the in vivo hemodynamics at the origin of the renal artery by measuring the velocity profiles and bifurcation geometry of a surgically exposed left renal artery in 10 anesthetized dogs. The angle between the aorta and the renal artery ranged from 60 degrees to 90 degrees (mean, 84 degrees) although the bifurcation did not lie in a single anterodorsal plane and the diameter of the renal artery ranged from 1.5 to 3.5 mm (mean, 2.4 mm). Despite different geometries, the velocity profiles in the different aortorenal bifurcations were similar. Although regions of reverse velocity were observed, the net flow in the renal artery was in the forward direction throughout the cardiac cycle. The peak Reynolds' number was 486 +/- 63. The velocity profiles in the proximal renal artery in the plane parallel to the bifurcation showed velocity vectors directed toward the caudal wall throughout the cardiac cycle. Reverse flow, indicating flow separation, was observed near the cranial wall even during systole. When the probe was placed on the cranial wall perpendicular to the wall, a velocity component from the cranial side to the caudal side was observed. At a distance of four diameters from the renal ostia, velocity profiles were almost parabolic. These results indicate that the velocity pattern near the cranial wall at the renal ostia, at which atherosclerotic lesions are prone to develop, are characterized by 1) a low time-averaged shear rate, 2) separation of the flow, and 3) a time-varying oscillation of the flow.}, } @article {pmid1750728, year = {1991}, author = {Vincent, JH and Aitken, RJ and Mark, D and Botham, RA}, title = {Scale model studies of the transport of airborne pollutants on coalfaces.}, journal = {The Annals of occupational hygiene}, volume = {35}, number = {4}, pages = {359-376}, doi = {10.1093/annhyg/35.4.359}, pmid = {1750728}, issn = {0003-4878}, mesh = {Air Movements ; Air Pollutants, Occupational/*analysis ; *Coal Mining ; Humans ; *Models, Structural ; Occupational Exposure ; Ventilation ; }, abstract = {Studies have been carried out to investigate airflows in coalmine models, with special regard to the transport of airborne pollutants, and to examine how they relate to what happens at full-scale in an actual underground mine. If such models can be shown to provide data representative of actual mine ventilation engineering, then they can provide cost-effective alternatives to full-scale investigations. The work set out in the first instance to identify the properties of: (a) the bulk airflow and associated transport of airborne pollutants along a longwall coalface; and (b) the transport of material out of regions that were partially enclosed or poorly ventilated (e.g. in the cutting zone, in headings). For the former, an appropriate quantity is the dispersivity of the coalface airflow, for the latter the mean retention time. Both quantities may be rendered non-dimensional with respect to dimensions characteristic of the system and to velocities of the airflow. Their behaviour in relation to a third dimensionless quantity, the flow Reynolds' number is also important. Experiments were performed, using smoke or dust tracers, to investigate how these properties are interrelated and how they scale between small-scale and full-scale systems. They were carried out in a 1/10-scale laboratory model, in a full-scale surface model, and underground in an actual coalmine. The basis of most of the experiments was the 'tracer decay' method, in which the transport properties of the aerodynamic system under investigation were determined from observations of the changes in tracer concentration with time immediately following the removal of the tracer source. During these experiments, the feasibility of using small-scale models to investigate ventilation problems was clearly indicated and preliminary scaling relationships which may be used as an initial basis for predicting the transport and local build-up of pollutants in mines were developed. It is expected that applications of the ideas and methodology described will be relevant to other industries.}, } @article {pmid1802650, year = {1991}, author = {Berg, HC}, title = {Bacterial motility: handedness and symmetry.}, journal = {Ciba Foundation symposium}, volume = {162}, number = {}, pages = {58-69; discussion 69-72}, doi = {10.1002/9780470514160.ch5}, pmid = {1802650}, issn = {0300-5208}, mesh = {*Bacterial Physiological Phenomena ; Cell Movement/*physiology ; Chemotaxis/physiology ; Chromatium ; Escherichia coli ; Flagella/*physiology ; Image Processing, Computer-Assisted ; Microscopy, Phase-Contrast ; }, abstract = {Many bacteria swim by rotating thin helical filaments that extend into the external medium, as with common bacteria, or run beneath the outer membrane, as with spirochetes. Each filament is driven at its base by a motor that turns alternately clockwise and counterclockwise. The motor-filament complex is called a flagellum. Other kinds of bacteria glide, but their organelles of locomotion are not known. Since bacteria are microscopic and live in an aqueous environment, they swim at low Reynolds' number; cyclic motion works (e.g. rotation of a helix) but reciprocal motion does not (e.g. stroking of a singly hinged oar). By measuring concentrations of certain chemicals as they move through their environment, making temporal comparisons and modulating the direction of flagellar rotation, bacteria accumulate in regions that they find more favourable. Studies of bacterial chemotaxis are highly advanced, particularly for the peritrichously flagellated species Escherichia coli. A great deal is known about chemoreception, receptor-flagellar coupling and adaptation. Recently it has been found that E. coli can aggregate in response to signals generated by the cells themselves. Complex patterns form with remarkable symmetries.}, } @article {pmid2304249, year = {1990}, author = {Yamada, H}, title = {[Effects of turbulence on gas transport during high frequency oscillation].}, journal = {Masui. The Japanese journal of anesthesiology}, volume = {39}, number = {1}, pages = {27-38}, pmid = {2304249}, issn = {0021-4892}, mesh = {*High-Frequency Ventilation ; Humans ; Models, Structural ; *Pulmonary Gas Exchange ; Trachea ; }, abstract = {To clarify the enhancing effect of turbulence on gas transfer in high frequency oscillation (HFO), the role of turbulence during oscillatory flow was studied. Oscillatory flow was generated in a straight circular tube as a trachea model, over the range of Reynolds' number (Re: 2000-16000) and Stokes parameter (lambda : 3-7). This simulates clinical settings. Measurements of the axial velocity were made by means of hot wire anemometer, and turbulence intensity (I) as well as ensemble mean velocity was calculated. At the same time, 1 ml of 100% CO2 was injected into the tube, and CO2 concentration was measured by a CO2 analyzer to yield the effective diffusivity (Deff). As Re increases and lambda decreases to a certain level, "conditional turbulence" appears in the whole cross section to produce an efficient lateral mixing. Deff increases with increasing I as well as Re, and increasing lambda results in an increase in the difference of measured and theoretical Deff (Watson's prediction for laminar oscillatory flow). It is concluded that turbulence during oscillatory flow plays an important role in lateral mixing to facilitate gas transport, and decision of ventilator settings is essential so as to give rise to "conditional turbulence" for the purpose of Deff augmentation during HFO.}, } @article {pmid3250628, year = {1988}, author = {Nomura, H and Ishikawa, C and Komatsuda, T and Ando, J and Kamiya, A}, title = {A disk-type apparatus for applying fluid shear stress on cultured endothelial cell.}, journal = {Biorheology}, volume = {25}, number = {3}, pages = {461-470}, doi = {10.3233/bir-1988-25307}, pmid = {3250628}, issn = {0006-355X}, mesh = {Cells, Cultured ; Endothelium, Vascular/*physiology ; Mathematics ; Methods ; Rheology ; Stress, Mechanical ; }, abstract = {To study the effect of fluid shear stress on cultured endothelial cells, we have developed an apparatus for the stress creation, which consists of a stainless steel disk driven by an electric DC motor and a stage to place a culture dish and to adjust the distance between the disk and the dish. When the disk is rotated, a concentric fluid movement occurs in the culture medium in the dish and exerts the shear stress on the endothelial cells cultured on the bottom of the dish. A theoretical analyses concerning the induced concentric flow velocity predicted that when the angular velocity of the disk rotation (omega) is slow enough to maintain a Reynolds' number of the order of 10, the exerted wall shear stress tau w on the endothelial cell monolayer is given for a constant as tau w = mu r omega/d where mu is the viscosity of the medium, d the distance from the plate to the monolayer and r the radial distance from the center of the dish. When omega is varied in a sinusoidal mode tau w also becomes sinusoidal, thus allowing to apply a pulsatile stress. In vitro experiments carried out to examine the validity of the theoretical results, using a suspension of polystyrene as a tracer with the ordinary culture medium and 99% ethanol, revealed excellent agreement of the measured velocity profiles with the predicted ones. The results demonstrated that the present apparatus can create both the steady and pulsatile wall shear stress on the culture cell layer as expected, unless Reynolds' number greatly exceeds the level of 10.}, } @article {pmid6693510, year = {1984}, author = {Kobari, M and Gotoh, F and Fukuuchi, Y and Tanaka, K and Suzuki, N and Uematsu, D}, title = {Blood flow velocity in the pial arteries of cats, with particular reference to the vessel diameter.}, journal = {Journal of cerebral blood flow and metabolism : official journal of the International Society of Cerebral Blood Flow and Metabolism}, volume = {4}, number = {1}, pages = {110-114}, doi = {10.1038/jcbfm.1984.15}, pmid = {6693510}, issn = {0271-678X}, mesh = {Animals ; Arteries/anatomy & histology/physiology ; Blood Flow Velocity ; Blood Pressure ; Cats ; Female ; Male ; Pia Mater/*blood supply ; Rheology ; }, abstract = {The blood flow velocity and diameter of feline pial arteries, ranging in diameter from 20 to 200 microns, were measured simultaneously using a newly developed video camera method under steady-state conditions for all other parameters. There was a linear relationship between blood flow velocity and pial artery diameter (y = 0.340x + 0.309), the correlation coefficient being 0.785 (p less than 0.001). The average values for blood flow velocity in pial arteries less than 50 microns, greater than or equal to 50 but less than 100 microns, greater than or equal to 100 but less than 150 microns, and greater than or equal to 150 microns in diameter were 12.9 +/- 1.3, 24.6 +/- 3.4, 42.1 +/- 4.7, and 59.9 +/- 5.3 mm/s, respectively. Blood flow rate was calculated as a product of the cross-sectional area and the flow velocity. The blood flow rate increased exponentially as the pial artery diameter increased (y = 2.71 X 10(-4) x2.98). The average values for blood flow rate in pial arteries less than 50 microns, greater than or equal to 50 but less than 100 microns, greater than or equal to 100 but less than 150 microns and greater than or equal to 150 microns in diameter were 12.8 +/- 1.5, 122.1 +/- 24.8, 510.2 +/- 74.8, and 1524.2 +/- 174.4 10(-3) mm3/s, respectively. Hemorheological parameters such as the wall shear rate and Reynolds' number were also calculated. The data obtained provide a useful basis for further investigations in the field of cerebral circulation.}, } @article {pmid7149035, year = {1982}, author = {Macagno, EO and Christensen, J and Lee, CL}, title = {Modeling the effect of wall movement on absorption in the intestine.}, journal = {The American journal of physiology}, volume = {243}, number = {6}, pages = {G541-50}, doi = {10.1152/ajpgi.1982.243.6.G541}, pmid = {7149035}, issn = {0002-9513}, support = {AM-08901/AM/NIADDK NIH HHS/United States ; }, mesh = {Animals ; *Gastrointestinal Motility ; *Intestinal Absorption ; Intestines/physiology ; Mathematics ; Models, Biological ; Muscle Contraction ; Muscle, Smooth/physiology ; Perfusion ; }, abstract = {Intestinal wall movements may influence intestinal absorption by inducing flow in the luminal volume. Direct evidence for this is scant and weak. Such evidence was sought by mechanical and analytical modeling. Wall motions resembling peristaltic ring contractions were induced in dialysis tubing filled with a concentrated salt solution and immersed in tap water. The disappearance of solute from the inside of the tube was monitored with conductivity probes and correlated with various kinds of wall motions. In analytical modeling, equations representing wall motions, flow, and mass transfer were constructed, with the assumptions that ring contractions are axisymmetric, the wall is totally compliant, the Reynolds' number is low, the fluid volume is conserved, the no-slip condition exists at the luminal surface, and inertial flow is negligible. In the mechanical model, wall motions caused a 30-35% increase in absorption that was matched in the corresponding analytical model. The analytical model demonstrated that the effect is progressively greater for nonpropagative stationary contractions, asymmetric progressive contractions, and symmetric progressive contractions, the increase being 33, 70, and 100%, respectively.}, } @article {pmid7298416, year = {1981}, author = {Slutsky, AS and Drazen, JM and O'Cain, CF and Ingram, RH}, title = {Alveolar pressure-airflow characteristics in humans breathing air, He-O2, and SF6-O2.}, journal = {Journal of applied physiology: respiratory, environmental and exercise physiology}, volume = {51}, number = {4}, pages = {1033-1037}, doi = {10.1152/jappl.1981.51.4.1033}, pmid = {7298416}, issn = {0161-7567}, support = {HL-00549/HL/NHLBI NIH HHS/United States ; HL-07118/HL/NHLBI NIH HHS/United States ; HL-16463/HL/NHLBI NIH HHS/United States ; }, mesh = {Adult ; *Air ; Airway Resistance ; *Fluorides ; *Helium ; Humans ; Male ; *Oxygen ; Pressure ; Pulmonary Alveoli/*physiology ; *Pulmonary Ventilation ; *Respiration ; *Sulfur Hexafluoride ; }, abstract = {In a system of rigid tubes under steady flow conditions, the coefficient of friction [CF = 2 delta P/(rho V2/A2)] (where delta P is pressure drop, rho is density, V is flow, and A is cross-sectional area) should be a unique function of Reynolds' number (Re). Recently it has been shown that at any given Re, the value of CF using transpulmonary pressure (PL) was lower when breathing He-O2 compared with air (Lisboa et al., J. Appl. Physiol.: Respirat. Environ. Exercise Physiol. 48: 878-885, 1980). One explanation for this discontinuity is that PL includes the pressure drop due to tissue viscance, which is independent of V, and thus would lead to an overestimate of CF on air compared with He-O2 at any Re. We tested this hypothesis by measuring V related to alveolar pressure, rather than PL, in normal subjects breathing air, He-O2, and SF6-O2. In each subject, for a given Re, CF was greatest breathing SF6-O2 and lowest breathing He-O2, similar to results using PL. Thus tissue viscance is not the sole cause of the discontinuous plot of CF vs. Re, and this phenomenon must be due to other factors, such as changing geometry or nonsteady behavior.}, } @article {pmid7303054, year = {1981}, author = {LoGerfo, FW and Crawshaw, HM and Nowak, M and Serrallach, E and Quist, WC and Valeri, CR}, title = {Effect of flow split on separation and stagnation in a model vascular bifurcation.}, journal = {Stroke}, volume = {12}, number = {5}, pages = {660-665}, doi = {10.1161/01.str.12.5.660}, pmid = {7303054}, issn = {0039-2499}, support = {H121796-02//PHS HHS/United States ; ONR NOOO 14-79-C-0168/ON/ONR/United States ; RR05487-16/RR/NCRR NIH HHS/United States ; }, mesh = {Biomechanical Phenomena ; *Blood Circulation ; Blood Flow Velocity ; Carotid Arteries/physiology ; *Models, Biological ; *Rheology ; }, abstract = {This is a study of the flow disturbance in a plastic model of an asymmetric vascular bifurcation. A sidearm was attached to the mainlimb at an angle of 15 degrees to the inlet flow axis. Water at steady flow was used and flow patterns were demonstrated by a dye injection technique. The proportion of inlet flow (Qi) exiting from the sidearm (Qs) was varied and flow patterns were recorded photographically. A laser Doppler anemometer (LDA) was used to measure near-wall velocity. At a physiologic Reynolds' number of 500, no flow disturbance occurred in the mainlimb when the sidearm was completely occluded. When the fraction of flow exiting from the sidearm (Qs/Qi) reached 0.19, a region of boundary layer separation developed along the wall of the mainlimb opposite the flow divider. This region of nearly static fluid spread circumferentially around the mainlimb as Qs/Qi increased. Near-wall velocity within the separation decreased and became negative when Qs/Qi = 0.31. When Qs/Qi reached 0.38, the separation enveloped the wall of the entire bifurcation with a shell of slowly moving fluid. At the same time, the rapidly moving mainstream impinged directly on the flow divider. There is a similarity between the region of separation seen in this model and the site of formation of atherosclerotic plaque at the carotid bifurcation. Separation may contribute to atherogenesis by creating a region of low wall shear at bifurcations.}, } @article {pmid7263418, year = {1981}, author = {Chang, HK and Mortola, JP}, title = {Fluid dynamic factors in tracheal pressure measurement.}, journal = {Journal of applied physiology: respiratory, environmental and exercise physiology}, volume = {51}, number = {1}, pages = {218-225}, doi = {10.1152/jappl.1981.51.1.218}, pmid = {7263418}, issn = {0161-7567}, mesh = {Airway Resistance ; Animals ; Humans ; Mathematics ; Pressure ; Trachea/*physiology ; }, abstract = {Because tracheal pressure measurement generally involves the use of a cannula or an endotracheal tube, fluid dynamic factors may cause a considerable artifact. We present a theoretical explanation of the observed apparent paradox in which the resistance of a tracheal cannula or an endotracheal tube is isolation was found to exceed the resistance of the airways plus the cannula or the tube in situ. By estimating the viscous dissipation and the kinetic energy change in a conduit with sudden variation of cross-sectional area, a predictive model is derived. The predictions are verified by a series of in vitro experiments with both steady and oscillatory flows. The experiments showed that the pressure recorded from the sidearm of a tracheal cannula or endotracheal tube contains an error which, in general, increased with the mean Reynolds' number of the through flow and also depends on the diameter ratio between the trachea and the tube or cannula, the position of the pressure tap, and the frequency of ventilation. When feasible, direct measurement with a needle in the trachea is suggested as a way to avoid the possible artifacts arising from the use fo a side tap of the cannula. Theoretical considerations, as well as in vitro and animal experiments, indicate that adding a properly chosen expansion to the tracheal cannula makes it possible to alter inspiratory and expiratory pressures selectively. This device may prove useful in control of breathing studies.}, } @article {pmid7204164, year = {1980}, author = {Slutsky, AS and Berdine, GG and Drazen, JM}, title = {Steady flow in a model of human central airways.}, journal = {Journal of applied physiology: respiratory, environmental and exercise physiology}, volume = {49}, number = {3}, pages = {417-423}, doi = {10.1152/jappl.1980.49.3.417}, pmid = {7204164}, issn = {0161-7567}, mesh = {Airway Resistance ; Humans ; Lung/*physiology ; Models, Anatomic ; Models, Biological ; *Respiration ; Rheology ; }, abstract = {We studied the pressure-flow relationships and flow distribution under steady conditions in a model of human central airways, over a range of tracheal Reynolds' numbers (350-30,000) by using air or helium. We found that the Moody diagram [log coefficient of friction CF = delta P/[1/2 rho (V2/A2)] vs. log Reynolds' number (Re)] had a slope of -1 for Re less than 500, a slope 0 for Re greater than 10,000, and slopes between -1 and 0 for 500 less than or equal to Re less than or equal to 10,000. The distribution of flow among branches was dependent on tracheal Reynolds' number so that, as tracheal Reynolds' number increased, the upper lobes received proportionally less of the total flow than the lower lobes. Because the airways in the upper lobes generally had greater branching angles than those in the lower lobes, this result was consistent with the hypothesis that the effective resistances introduced by branching angles was flow dependent, increasing proportionally more the greater the angle.}, } @article {pmid7451298, year = {1980}, author = {Lisboa, C and Wood, LD and Jardim, J and Macklem, PT}, title = {Relation between flow, curvilinearity, and density dependence of pulmonary pressure-flow curves.}, journal = {Journal of applied physiology: respiratory, environmental and exercise physiology}, volume = {48}, number = {5}, pages = {878-885}, doi = {10.1152/jappl.1980.48.5.878}, pmid = {7451298}, issn = {0161-7567}, mesh = {Adult ; *Airway Resistance ; Bronchi/anatomy & histology/physiology ; Female ; Gases/analysis ; Humans ; Lung/physiology ; Lung Volume Measurements ; Male ; Pressure ; *Pulmonary Ventilation ; Respiratory System/*anatomy & histology ; Trachea/anatomy & histology/physiology ; }, abstract = {In nine normal subjects we measured pulmonary pressure-flow curves by ensemble averaging over 20 breaths and solving the equation P = K'V alpha where P is flow-resistive pressure, K' is slope, 5 V is flow, and alpha is curvilinearity. The study was performed at four lung volumes from 37 to 73% of total lung capacity, with the subjects breathing air or HeO2. K' was lower at every lung volume during HeO2 breathing, whereas the exponent alpha was uninfluenced by either lung volume or HeO2 breathing. Although alpha increased with flow rate, comparison of air and HeO2 curves revealed that alpha was not uniquely related to Reynolds' number. Furthermore there was no correlation between curvilinearity and the density dependence of K'. These observations are inconsistent with the general equation P = KV alpha rho alpha-1 mu 2-alpha, where K is a constant related to airway geometry, rho is density and mu is viscosity. (Wood et al., J. Appl. Physiol. 41: 234-244, 1976). The reasons for this discrepancy are unclear, but do not appear to be related to effects of oscillatory flow because alpha was similar from 20 to 90 breaths/min in four subjects. We conclude that the curvilinearity of pulmonary pressure-flow curves is related to flow but independent of gas density and is not explicable solely on the basis of Reynolds' number.}, } @article {pmid7349947, year = {1980}, author = {Wall, MA}, title = {Infant endotracheal tube resistance: effects of changing length, diameter, and gas density.}, journal = {Critical care medicine}, volume = {8}, number = {1}, pages = {38-40}, pmid = {7349947}, issn = {0090-3493}, mesh = {Air ; *Airway Resistance ; Biomechanical Phenomena ; Helium ; Humans ; Infant ; *Intubation, Intratracheal ; Oxygen ; Pulmonary Ventilation ; }, abstract = {Endotracheal tube resistance may increase upper airway resistance and the work of breathing beyond the normal range in adults of children who are chronically intubated and receiving intermittent mandatory ventilation. The purpose of this study was to measure the resistance of infant endotracheal tubes (IETTs) over the range of normal infant respiratory flows while systematically changing length, diameter, and carrier gas density. Resistance was measured in IETTs of 2.5, 3.0, and 3.5 mm inner diameter at flows increasing from 10--150 ml/sec, using both air and 80% helium- 20% oxygen (He-O2) as the carrier gases. Tube length was progressively shortened from full length to 4.8 cm in 2-cm increments, and resistance to both air and He-O2 was measured at all lengths. Reynolds' number calculations and the relationship of resistance to flow showed the flow regime in IETTs to be transitional in nature. Increasing tube diameter, decreasing length, or decreasing gas density led to large decreases in IETT flow resistance. Over the range of normal infant flows, IETT resistance is equal to or higher than that of the normal upper aiaway. IETT resistance might increase the work of breathing in some infants to the point of respiratory failure, and such resistance may be lowered by systematic changes in IETT diameter, length, or carrier gas density.}, } @article {pmid6906133, year = {1980}, author = {Eriksson, A and Svedbergh, B}, title = {Transcellular aqueous humor outflow: a theoretical and experimental study.}, journal = {Albrecht von Graefes Archiv fur klinische und experimentelle Ophthalmologie. Albrecht von Graefe's archive for clinical and experimental ophthalmology}, volume = {212}, number = {3-4}, pages = {187-197}, pmid = {6906133}, issn = {0065-6100}, support = {N0. R01-EY00475/EY/NEI NIH HHS/United States ; }, mesh = {Animals ; Aqueous Humor/*physiology ; Humans ; Macaca fascicularis ; Models, Biological ; Rheology ; Viscosity ; }, abstract = {When the aqueous humor passed through the transcellular channels of the inner wall endothelium of Schlemm's canal the flow was estimated to be very slow and viscous (Reynolds' number about 10(-3)). It was found to be accurate to treat this extreme flow situation with conventional hydrodynamic formulae without specific corrections. Four different principal configurations of the transcellular channels were investigated. The theoretical calculations yielded results in good agreement with those obtained from the experimental model studies. Where deviations occurred they were probably explained by a radial flow component, which was not incorporated in the theoretical formulae applied. A spherical channel configuration was considered most similar to the in vivo situation and this yielded experimental resistance values half those of previously applied theoretical methods. Using previous morphological data the present results indicated that less than 5% of the total resistance to aqueous humor outflow was located in the inner wall endothelium in normal human eyes, and about 10% in cynomolgus monkey eyes at normal intraocular pressures.}, } @article {pmid511719, year = {1979}, author = {Johnston, JR and Schroter, RC}, title = {Deposition of particles in model airways.}, journal = {Journal of applied physiology: respiratory, environmental and exercise physiology}, volume = {47}, number = {5}, pages = {947-953}, doi = {10.1152/jappl.1979.47.5.947}, pmid = {511719}, issn = {0161-7567}, mesh = {Aerosols ; Lung/*physiology ; Mathematics ; *Models, Anatomic ; *Models, Structural ; }, abstract = {The deposition of monodisperse aerosols in models of single lung airway bifurcations was studied. The particles, generated by spinning disk, were in the size range of 4.2--8.8 microns (density 1.3 X 10(3) kg . m-3). The model bifurcations were symmetrical, of physiological size, and based on established morphological data. The effects on percentage deposition (P) of flow rate (expressed as Reynolds' number. Re), particle diameter (d), tube diameter (D), and bifurcation angle (2 theta) were studied and a generalized expression for deposition based on these variables was obtained, viz., P = 11.04 X 10(5) Re (d/D)2.5sin3 theta. The applicability of this equation is discussed.}, } @article {pmid329294, year = {1977}, author = {Patel, IC and Sirs, JA}, title = {Indicator dilution measurements of flow parameters in curved tubes and branching networks.}, journal = {Physics in medicine and biology}, volume = {22}, number = {4}, pages = {714-730}, doi = {10.1088/0031-9155/22/4/005}, pmid = {329294}, issn = {0031-9155}, mesh = {Blood ; Iodine Radioisotopes ; Isotonic Solutions ; Plasma ; Potassium Chloride ; *Radioisotope Dilution Technique ; Serum Albumin, Radio-Iodinated ; Sodium Chloride ; }, abstract = {An experimental investigation has been made of the application of the indicator-dilution bolus-injection technique to measure flow rate, mean transit time and vessel volume with steady flow in curved tubes and branching networks. Measurements were made with 131I in 2N KCl and 131I-human serum albumin in isotonic saline, plasma and whole blood under laminar flow conditions up to a Reynolds' number of 460. The flow rate estimations are more reliable than those obtained for flow through straight tubes, due to secondary flows tending to disperse the indicator uniformly over the vessel cross-section. Even so, estimations of mean transit time and vessel volumes, using accepted theoretical formulae, may be as much as 200% in error. Similar measurements have been made of the flow parameters with bifurcations and branching networks. The indicator is not partitioned between the branches in proportion to the flow rate, as is assumed in the original indicator dilution theory, except when there is complete symmetry of the flow. An alternative method of estimating the vessel volume was used and shown to give an accurate estimate of the true volume in these circumstances.}, } @article {pmid36405040, year = {2022}, author = {Kaziz, S and Ben Mariem, I and Echouchene, F and Belkhiria, M and Belmabrouk, H}, title = {Taguchi optimization of integrated flow microfluidic biosensor for COVID-19 detection.}, journal = {European physical journal plus}, volume = {137}, number = {11}, pages = {1235}, doi = {10.1140/epjp/s13360-022-03457-1}, pmid = {36405040}, issn = {2190-5444}, abstract = {In this research, Taguchi's method was employed to optimize the performance of a microfluidic biosensor with an integrated flow confinement for rapid detection of the SARS-CoV-2. The finite element method was used to solve the physical model which has been first validated by comparison with experimental results. The novelty of this study is the use of the Taguchi approach in the optimization analysis. An L 8 2 7 orthogonal array of seven critical parameters-Reynolds number (Re), Damköhler number (Da), relative adsorption capacity (σ), equilibrium dissociation constant (KD), Schmidt number (Sc), confinement coefficient (α) and dimensionless confinement position (X), with two levels was designed. Analysis of variance (ANOVA) methods are also used to calculate the contribution of each parameter. The optimal combination of these key parameters was Re = 10[-2], Da = 1000, σ = 0.5, K D = 5, Sc = 10[5], α = 2 and X = 2 to achieve the lowest dimensionless response time (0.11). Among the all-optimization factors, the relative adsorption capacity (σ) has the highest contribution (37%) to the reduction of the response time, while the Schmidt number (Sc) has the lowest contribution (7%).}, } @article {pmid36399789, year = {2022}, author = {Jhun, CS and Xu, L and Siedlecki, C and Bartoli, CR and Yeager, E and Lukic, B and Scheib, CM and Newswanger, R and Cysyk, JP and Shen, C and Bohnenberger, K and Weiss, WJ and Rosenberg, G}, title = {Kinetic and Dynamic Effects on Degradation of von Willebrand Factor.}, journal = {ASAIO journal (American Society for Artificial Internal Organs : 1992)}, volume = {}, number = {}, pages = {}, doi = {10.1097/MAT.0000000000001848}, pmid = {36399789}, issn = {1538-943X}, abstract = {The loss of high molecular weight multimers (HMWM) of von Willebrand factor (vWF) in aortic stenosis (AS) and continuous-flow left ventricular assist devices (cf-LVADs) is believed to be associated with high turbulent blood shear. The objective of this study is to understand the degradation mechanism of HMWM in terms of exposure time (kinetic) and flow regime (dynamics) within clinically relevant pathophysiologic conditions. A custom high-shear rotary device capable of creating fully controlled exposure times and flows was used. The system was set so that human platelet-poor plasma flowed through at 1.75 ml/sec, 0.76 ml/sec, or 0.38 ml/sec resulting in the exposure time (texp) of 22, 50, or 100 ms, respectively. The flow was characterized by the Reynolds number (Re). The device was run under laminar (Re = 1,500), transitional (Re = 3,000; Re = 3,500), and turbulent (Re = 4,500) conditions at a given texp followed by multimer analysis. No degradation was observed at laminar flow at all given texp. Degradation of HMWM at a given texp increases with the Re. Re (p < 0.0001) and texp (p = 0.0034) are significant factors in the degradation of HMWM. Interaction between Re and texp, however, is not always significant (p = 0.73). http://links.lww.com/ASAIO/A920.}, } @article {pmid36399753, year = {2022}, author = {Bermudez, G and Alexakis, A}, title = {Saturation of Turbulent Helical Dynamos.}, journal = {Physical review letters}, volume = {129}, number = {19}, pages = {195101}, doi = {10.1103/PhysRevLett.129.195101}, pmid = {36399753}, issn = {1079-7114}, abstract = {The presence of large scale magnetic fields in nature is often attributed to the inverse cascade of magnetic helicity driven by turbulent helical dynamos. In this Letter, we show that in turbulent helical dynamos, the inverse flux of magnetic helicity toward the large scales Π_{H} is bounded by |Π_{H} |≤cεk_{η} ^{-1}, where ε is the energy injection rate, k_{η} is the Kolmogorov magnetic dissipation wave number, and c an order one constant. Assuming the classical isotropic turbulence scaling, the inverse flux of magnetic helicity Π_{H} decreases at least as a -3/4 power law with the magnetic Reynolds number Rm: |Π_{H} |≤cεℓ_{f} Rm^{-3/4} max[Pm,1]^{1/4}, where Pm is the magnetic Prandtl number and ℓ_{f} the forcing length scale. We demonstrate this scaling with Rm using direct numerical simulations of turbulent dynamos forced at intermediate scales. The results further indicate that nonlinear saturation is achieved by a balance between the inverse cascade and dissipation at domain size scales L for which the saturation value of the magnetic energy is bounded by E_{m} ≤cL(εℓ_{f} )^{2/3} Rm^{1/4} max[1,Pm]^{1/4} . Numerical simulations also demonstrate this bound. These results are independent of the dynamo mechanism considered. In our setup, they imply that inviscid mechanisms cannot explain large scale magnetic fields and have critical implications for the modeling of astrophysical dynamos.}, } @article {pmid36397500, year = {2022}, author = {Budanur, NB and Kantz, H}, title = {Scale-dependent error growth in Navier-Stokes simulations.}, journal = {Physical review. E}, volume = {106}, number = {4-2}, pages = {045102}, doi = {10.1103/PhysRevE.106.045102}, pmid = {36397500}, issn = {2470-0053}, abstract = {We estimate the maximal Lyapunov exponent at different resolutions and Reynolds numbers in large eddy simulations (LES) and direct numerical simulations of sinusoidally driven Navier-Stokes equations in three dimensions. Independent of the Reynolds number when nondimensionalized by Kolmogorov units, the LES Lyapunov exponent diverges as an inverse power of the effective grid spacing showing that the fine scale structures exhibit much faster error growth rates than the larger ones. Effectively, i.e., ignoring the cutoff of this phenomenon at the Kolmogorov scale, this behavior introduces an upper bound to the prediction horizon that can be achieved by improving the precision of initial conditions through refining of the measurement grid.}, } @article {pmid36388976, year = {2022}, author = {Yao, N and Wang, H and Wang, B and Wang, X and Huang, J}, title = {Convective thermal cloaks with homogeneous and isotropic parameters and drag-free characteristics for viscous potential flows.}, journal = {iScience}, volume = {25}, number = {11}, pages = {105461}, doi = {10.1016/j.isci.2022.105461}, pmid = {36388976}, issn = {2589-0042}, abstract = {Although convective thermal cloaking has been advanced significantly, the majority of related researches have concentrated on creeping viscous potential flows. Here, we consider convective thermal cloaking works in non-creeping viscous potential flows, and propose a combination of the separation of variables method and the equivalent-medium integral method to analytically deduce the parameters of convective thermal cloaks with isotropic-homogeneous dynamic viscosity and thermal conductivity. Through numerical simulation, we demonstrate the cloaks can hide the object from thermo-hydrodynamic fields. Besides, by comparing the drag force cloaks bear in cloak case and the objects bear in object-existent case, we find convective thermal cloaks can considerably reduce the drag force, which appears drag-free characteristics. Finally, it is our hope that these developed methods can reduce the difficulties of metadevices fabrications, promote the development of drag reduction technology under higher Reynolds number, and shed light on the control of other multi-physics systems.}, } @article {pmid36384832, year = {2022}, author = {Cao, BZ and Wang, J and Zhao, YJ and Liu, C}, title = {[Hydrodynamic characteristics of grass swale runoff in Guanzhong area of Loess Plateau, Northwest China.].}, journal = {Ying yong sheng tai xue bao = The journal of applied ecology}, volume = {33}, number = {11}, pages = {2979-2986}, doi = {10.13287/j.1001-9332.202211.023}, pmid = {36384832}, issn = {1001-9332}, abstract = {Grass swale has been widely used in sponge city construction, which can effectively improve the urban ecological environment. To explore the regulation mechanism of runoff in grass swale, runoff scouring experiment was carried out to study the hydrodynamic characteristics of runoff and the distribution of cross-section velocity under the combined conditions of five slopes (1%, 2%, 3%, 4%, 5%) and five scour flows (20, 30, 40, 50, 60 L·min[-1]). With the increases of flow rate and slope, flow velocity, Reynolds number and Froude number all increased gradually, while the Manning roughness coefficient and Darcy-Weisbach friction coefficient decreased gradually. The velocity (V) could be expressed as a power function V=0.3387Q[0.555]S[0.6601] of flow rate (Q) and slope (S). The variation ranges of Reynolds number and Froude number were 1160.95-6596.82 and 0.17-1.21, respectively. The runoff flow patterns were all turbulent. The flow pattern was greatly affected by the slope. When flow rate and slope were small, they had great influence on friction coefficient. Under the experimental conditions, the Darcy-Weisbach friction coefficient was negatively correlated with Reynolds number. The velocity distribution of cross-section showed symmetrical distribution on both sides of the center. The maximum velocity point was located at the center of water surface. With the increases of flow rate and slope, the velocity contours of cross section gradually became dense and the gradient of the velocity change increased. Our results provide a theoretical basis for the design, application and hydraulic calculation of grass swale in the construction of sponge cities in loess areas, and reveal the runoff regulation mechanism by analyzing the hydraulic characteristics of grass swale runoff.}, } @article {pmid36383261, year = {2022}, author = {Karami, A and Ranjbar, B and Rahimi, M and Mohammadi, F}, title = {Novel hybrid neuro-fuzzy model to anticipate the heat transfer in a heat exchanger equipped with a new type of self-rotating tube insert.}, journal = {The European physical journal. E, Soft matter}, volume = {45}, number = {11}, pages = {92}, doi = {10.1140/epje/s10189-022-00248-5}, pmid = {36383261}, issn = {1292-895X}, abstract = {In this investigation, a combination of the wingsuit flying search (WFS) and teaching-learning-based optimization (TLBO) algorithms is developed as a new combinatorial optimization algorithm. The proposed combinatorial algorithm is tested over some well-known benchmark functions and then integrated with the artificial neural network (ANN) to construct a novel hybrid model. After that, the obtained hybrid model is employed to anticipate the experimentally obtained values of the average Nusselt number (Nu), average friction coefficient (f) as well as thermal-hydraulic performance ratio (η), in a heat exchanger equipped with a new type of self-rotating tube insert, against governing parameters. The insert is placed in the tube side of the water heater to heat natural gas. The proposed insert consists of various numbers of self-rotating modules. Indeed, the rotating insert is introduced to create effective secondary sweeping flow on the inner side of the tube. Since this type of tube insert simultaneously provides heat transfer enhancement and undesired pressure drop, a thermal-hydraulic performance ratio is defined to consider both of them. The governing parameters are the number of inserts (0 ≤ N ≤ 30), reservoir's temperature (40 °C ≤ TR ≤ 50 °C) as well as Reynolds number (6 × 10[3] ≤ Re ≤ 18 × 10[3]). It was found that the WFS-TLBO enhances the effectiveness of the main ANN in anticipating the Nusselt number (Nu), average friction coefficient (f) as well as performance ratio (η). Moreover, introducing the WFS-TLBO algorithm into the neural network provides an enhancement in the effectiveness of the hybrid models based on the single WFS and TLBO algorithms in anticipating the same parameters.}, } @article {pmid36378533, year = {2022}, author = {Wei, SX and Yang, H and Au, CT and Xie, TL and Yin, SF}, title = {Mixing Characteristic and High-Throughput Synthesis of Cadmium Sulfide Nanoparticles with Cubic Hexagonal Phase Junctions in a Chaotic Millireactor.}, journal = {Langmuir : the ACS journal of surfaces and colloids}, volume = {}, number = {}, pages = {}, doi = {10.1021/acs.langmuir.2c02087}, pmid = {36378533}, issn = {1520-5827}, abstract = {A four-stage oscillating feedback millireactor with splitters (S-OFM) was designed to improve the mixing performance based on chaotic advection. Three-dimensional CFD simulations were used to investigate its flow characteristics and mixing performance, and the generation mechanisms of secondary flows were examined. The results show that the mixing index (MIcup) increased with the increase in the Reynolds number (Re), and MIcup could reach 99.8% at Re = 663. Poincaré mapping and Kolmogorov entropy were adopted to characterize the chaotic advection intensity, which indicates that there is a intensity increase with the increase in Re. In addition, the results of Villermaux-Dushman experiments demonstrate that S-OFM performs excellently, and the mixing time could reach 1.04 ms at Re = 2764. Finally, S-OFM was successfully used to synthesize CdS nanoparticles with cubic hexagonal phase junctions. At a flow rate of 180 mL/min, the average particle size was 10.5 nm and the particle size distribution was narrow (with a coefficient of variation of 0.14).}, } @article {pmid36374705, year = {2022}, author = {Antunes, GC and Malgaretti, P and Harting, J and Dietrich, S}, title = {Pumping and Mixing in Active Pores.}, journal = {Physical review letters}, volume = {129}, number = {18}, pages = {188003}, doi = {10.1103/PhysRevLett.129.188003}, pmid = {36374705}, issn = {1079-7114}, abstract = {We show both numerically and analytically that a chemically patterned active pore can act as a micro- or nanopump for fluids, even if it is fore-aft symmetric. This is possible due to a spontaneous symmetry breaking which occurs when advection rather than diffusion is the dominant mechanism of solute transport. We further demonstrate that, for pumping and tuning the flow rate, a combination of geometrical and chemical inhomogeneities is required. For certain parameter values, the flow is unsteady, and persistent oscillations with a tunable frequency appear. Finally, we find that the flow exhibits convection rolls and hence promotes mixing in the low Reynolds number regime.}, } @article {pmid36374283, year = {2022}, author = {Hopkins, CC and Shen, AQ and Haward, SJ}, title = {Effect of blockage ratio on flow of a viscoelastic wormlike micellar solution past a cylinder in a microchannel.}, journal = {Soft matter}, volume = {}, number = {}, pages = {}, doi = {10.1039/d2sm01162j}, pmid = {36374283}, issn = {1744-6848}, abstract = {We present experiments on the flow of a viscoelastic wormlike micellar solution around cylinders (radius R) confined in straight microchannels (width W). Thirteen flow geometries are tested where the blockage ratio is varied over a wide range 0.055 ≤ BR = 2R/W ≤ 0.63. Experiments are performed at negligible Reynolds number, and for Weissenberg numbers Wi = λU/R up to 1000, where U is the average flow speed and λ is the relaxation time of the fluid. Micro-particle image velocimetry is used to characterise the flow state at each BR and Wi. In all of the geometries, a first critical Weissenberg number marks a transition from symmetric flow to an asymmetric but time-steady flow state, while a second higher critical Weissenberg number marks the onset of time-dependent flows. However, we report a clear shift in behaviour over a narrow intermediate range of 0.33 ≲ BR ≲ 0.41. Channels with BR ≤ 0.33 fall in a 'low' BR regime, with instabilities that originate from the downstream stagnation point, while those with BR ≥ 0.44 fall in a 'high' BR regime, with instabilities developing at the upstream stagnation point. Behaviour within the newly-identified intermediate BR regime is complex due to the competing influence of the two stagnation points. We summarise all our results in a flow state diagram covering Wi-BR parameter space, clearly defining the different regimes of blockage ratio for the first time. Our results contribute to the understanding of the complexities of viscoelastic flow in this benchmark geometry.}, } @article {pmid36369608, year = {2022}, author = {Chen, Y and Feng, X and Shi, X and Cai, W and Li, B and Zhao, Y}, title = {Evaluation of computational fluid dynamics models for predicting pediatric upper airway airflow characteristics.}, journal = {Medical & biological engineering & computing}, volume = {}, number = {}, pages = {}, pmid = {36369608}, issn = {1741-0444}, support = {IR2021211//harbin institute of technology/ ; }, abstract = {Computational fluid dynamics (CFD) has the potential for use as a clinical tool to predict the aerodynamics and respiratory function in the upper airway (UA) of children; however, careful selection of validated computational models is necessary. This study constructed a 3D model of the pediatric UA based on cone beam computed tomography (CBCT) imaging. The pediatric UA was 3D printed for pressure and velocity experiments, which were used as reference standards to validate the CFD simulation models. Static wall pressure and velocity distribution inside of the UA under inhale airflow rates from 0 to 266.67 mL/s were studied by CFD simulations based on the large eddy simulation (LES) model and four Reynolds-averaged Navier-Stokes (RANS) models. Our results showed that the LES performed best for pressure prediction; however, it was much more time-consuming than the four RANS models. Among the RANS models, the Low Reynolds number (LRN) SST k-ω model had the best overall performance at a series of airflow rates. Central flow velocity determined by particle image velocimetry was 3.617 m/s, while velocities predicted by the LES, LRN SST k-ω, and k-ω models were 3.681, 3.532, and 3.439 m/s, respectively. All models predicted jet flow in the oropharynx. These results suggest that the above CFD models have acceptable accuracy for predicting pediatric UA aerodynamics and that the LRN SST k-ω model has the most potential for clinical application in pediatric respiratory studies.}, } @article {pmid36365668, year = {2022}, author = {de Araujo, MT and Furlan, L and Brandi, A and Souza, L}, title = {A Semi-Analytical Method for Channel and Pipe Flows for the Linear Phan-Thien-Tanner Fluid Model with a Solvent Contribution.}, journal = {Polymers}, volume = {14}, number = {21}, pages = {}, doi = {10.3390/polym14214675}, pmid = {36365668}, issn = {2073-4360}, support = {2013/07375-0//São Paulo Research Foundation/ ; 001//Coordenação de Aperfeicoamento de Pessoal de Nível Superior/ ; }, abstract = {This work presents a semi-analytical method for laminar steady-state channel and pipe flows of viscoelastic fluids using the Linear Phan-Thien-Tanner (LPTT) constitutive equation, with solvent viscosity contribution. For the semi-analytical method validation, it compares its results and two analytical solutions: the Oldroyd-B model and the simplified LPTT model (without solvent viscosity contribution). The results adopted different values of the dimensionless parameters, showing their influence on the viscoelastic fluid flow. The results include the distribution of the streamwise velocity component and the extra-stress tensor components in the wall-normal direction. In order to investigate the proposed semi-analytical method, different solutions were obtained, both for channel and pipe flows, considering different values of Reynolds number, solvent viscosity contribution in the homogeneous mixture, elongational parameter, shear parameter, and Weissenberg number. The results show that the proposed semi-analytical method can find a laminar solution using the non-Newtonian LPTT model with solvent viscosity contribution and verify the effect of the parameters in the resulting flow field.}, } @article {pmid36364597, year = {2022}, author = {Baig, MF and Chen, GM and Tso, CP}, title = {The Thermal Performance Analysis of an Al2O3-Water Nanofluid Flow in a Composite Microchannel.}, journal = {Nanomaterials (Basel, Switzerland)}, volume = {12}, number = {21}, pages = {}, doi = {10.3390/nano12213821}, pmid = {36364597}, issn = {2079-4991}, support = {FRGS/1/2019/TK03/MMU/02/1.//Ministry of Higher Education Malaysia/ ; }, abstract = {Partial filling of porous medium insert in a channel alleviates the tremendous pressure drop associated with a porous medium saturated channel, and enhances heat transfer at an optimum fraction of porous medium filling. This study pioneered an investigation into the viscous dissipative forced convective heat transfer in a parallel-plate channel, partially occupied with a porous medium at the core, under local thermal non-equilibrium condition. Solving the thermal energy equation along the Darcy-Brinkman equation, new exact temperature fields and Nusselt number are presented under symmetrical isoflux thermal boundary condition. Noteworthy is the heat flux bifurcation at the interface between the clear fluid and porous medium driven by viscous dissipation, in cases where the combined hydrodynamic resistance to fluid flow and thermal resistance to fluid conduction is considerable in low Darcy number porous medium insert. However, viscous dissipation does not affect the qualitative variation of the Nusselt number with the fraction of porous medium filling. By using Al2O3-Water nanofluid as the working fluid in a uniformly heated microchannel, partially filled with an optimum volume fraction of porous medium, the heat transfer coefficient improves as compared to utilizing water. The accompanied viscous dissipation however has a more adverse impact on the heat transfer coefficient of nanofluids with an increasing Reynolds number.}, } @article {pmid36363954, year = {2022}, author = {Chen, Z and Wang, Y and Zhou, S}, title = {Numerical Analysis of Mixing Performance in an Electroosmotic Micromixer with Cosine Channel Walls.}, journal = {Micromachines}, volume = {13}, number = {11}, pages = {}, doi = {10.3390/mi13111933}, pmid = {36363954}, issn = {2072-666X}, support = {51705184//National Natural Science Foundation of China/ ; GDZB-062//Program for Distinguished Talents of Six Domains in Jiangsu Province of China/ ; SJCX22_1671//Jiangsu Province Graduate Research and Practice Innovation Program Project/ ; }, abstract = {Micromixers have significant potential in the field of chemical synthesis and biological pharmaceuticals, etc. In this study, the design and numerical simulations of a passive micromixer and a novel active electroosmotic micromixer by assembling electrode pairs were both presented with a cosine channel wall. The finite element method (FEM) coupled with Multiphysics modeling was used. To propose an efficient micromixer structure, firstly, different geometrical parameters such as amplitude-to-wavelength ratio (a/c) and mixing units (N) in the steady state without an electric field were investigated. This paper aims to seek a high-quality mixing solution. Therefore, based on the optimization of the above parameters of the passive micromixer, a new type of electroosmotic micromixer with an AC electric field was proposed. The results show that the vortices generated by electroosmosis can effectively induce fluid mixing. The effects of key parameters such as the Reynolds number, the number of electrode pairs, phase shift, voltage, and electrode frequency on the mixing performance were specifically discussed through numerical analysis. The mixing efficiency of the electroosmotic micromixer is quantitatively analyzed, which can be achieved at 96%. The proposed micromixer has a simple structure that can obtain a fast response and high mixing index.}, } @article {pmid36363898, year = {2022}, author = {Dai, Y and Cha, H and Nguyen, NK and Ouyang, L and Galogahi, F and Yadav, AS and An, H and Zhang, J and Ooi, CH and Nguyen, NT}, title = {Dynamic Behaviours of Monodisperse Double Emulsion Formation in a Tri-Axial Capillary Device.}, journal = {Micromachines}, volume = {13}, number = {11}, pages = {}, doi = {10.3390/mi13111877}, pmid = {36363898}, issn = {2072-666X}, support = {DP220100261//Australian Research Council/ ; }, abstract = {We investigated experimentally, analytically, and numerically the formation process of double emulsion formations under a dripping regime in a tri-axial co-flow capillary device. The results show that mismatches of core and shell droplets under a given flow condition can be captured both experimentally and numerically. We propose a semi-analytical model using the match ratio between the pinch-off length of the shell droplet and the product of the core growth rate and its pinch-off time. The mismatch issue can be avoided if the match ratio is lower than unity. We considered a model with the wall effect to predict the size of the matched double emulsion. The model shows slight deviations with experimental data if the Reynolds number of the continuous phase is lower than 0.06 but asymptotically approaches good agreement if the Reynolds number increases from 0.06 to 0.14. The numerical simulation generally agrees with the experiments under various flow conditions.}, } @article {pmid36363842, year = {2022}, author = {Cao, M and Cao, S and Zhao, J and Zhu, J}, title = {Numerical Study of Thermal Enhancement in a Single- and Double-Layer Microchannel Heat Sink with Different Ribs.}, journal = {Micromachines}, volume = {13}, number = {11}, pages = {}, doi = {10.3390/mi13111821}, pmid = {36363842}, issn = {2072-666X}, abstract = {In this paper, a microchannel heat sink model was proposed to realize single- and double- layer flow through built-in ribs. The finite element volume method was used to analyze the influence of the length, thickness and angle of the inner rib on the flow and heat transfer characteristics of the microchannel heat sink. The pressure drop, temperature field, flow field, and thermal characteristics are given. The numerical simulation results show that the rectangular rib plate makes the fluid in the microchannel heat sink flow alternately in the upper and lower layers, which can effectively enhance heat transfer. However, with the increase in rib length, the comprehensive evaluation factor decreases. The change of the angle of the rectangular rib plate has little influence on the Nusselt number. The change rate of the comprehensive evaluation factor of the thickness of the rectangular rib plate is the largest. When the Reynolds number is 1724, the comprehensive evaluation factor of Case 9 is 4.7% higher than that of Case 2. According to the parameter study of the built-in rib plate, the optimal parameter combination is given, in which the angle is 0°, the length is 7.5 mm, and the thickness is 0.2-0.3 mm.}, } @article {pmid36363584, year = {2022}, author = {Cancilla, N and Tamburini, A and Tarantino, A and Visconti, S and Ciofalo, M}, title = {Friction and Heat Transfer in Membrane Distillation Channels: An Experimental Study on Conventional and Novel Spacers.}, journal = {Membranes}, volume = {12}, number = {11}, pages = {}, doi = {10.3390/membranes12111029}, pmid = {36363584}, issn = {2077-0375}, abstract = {The results of an experimental investigation on pressure drop and heat transfer in spacer-filled plane channels, which are representative of Membrane Distillation units, are presented and discussed. Local and mean heat transfer coefficients were obtained by using Thermochromic Liquid Crystals and Digital Image Processing. The performances of a novel spacer geometry, consisting of spheres that are connected by cylindrical rods, and are hereafter named spheres spacers, were compared with those of more conventional woven and overlapped spacers at equal values of the Reynolds number Re (in the range ~150 to ~2500), the pitch-to-channel height ratio, the flow attack angle and the thermal boundary conditions (two-side heat transfer). For any flow rate, the novel spacer geometry provided the least friction coefficient and a mean Nusselt number intermediate between those of the overlapped and the woven spacers. For any pressure drop and for any pumping power, the novel spacer provided the highest mean Nusselt number over the whole Reynolds number range that was investigated. The influence of buoyancy was also assessed for the case of the horizontal channels. Under the experimental conditions (channel height H ≈ 1 cm, ΔT ≈ 10 °C), it was found to be large in empty (spacer-less) channels that were up to Re ≈ 1200 (corresponding to a Richardson number Ri of ~0.1), but it was much smaller and limited to the range Re < ~500 (Ri < ~0.5) in the spacer-filled channels.}, } @article {pmid36359756, year = {2022}, author = {Soulsbury, CD and Humphries, S}, title = {Biophysical Determinants and Constraints on Sperm Swimming Velocity.}, journal = {Cells}, volume = {11}, number = {21}, pages = {}, doi = {10.3390/cells11213360}, pmid = {36359756}, issn = {2073-4409}, mesh = {Animals ; Male ; *Sperm Motility ; *Semen ; Spermatozoa ; Biological Evolution ; Flagella ; }, abstract = {Over the last 50 years, sperm competition has become increasingly recognised as a potent evolutionary force shaping male ejaculate traits. One such trait is sperm swimming speed, with faster sperm associated with increased fertilisation success in some species. Consequently, sperm are often thought to have evolved to be longer in order to facilitate faster movement. However, despite the intrinsic appeal of this argument, sperm operate in a different biophysical environment than we are used to, and instead increasing length may not necessarily be associated with higher velocity. Here, we test four predictive models (ConstantPower Density, Constant Speed, Constant Power Transfer, Constant Force) of the relationship between sperm length and speed. We collated published data on sperm morphology and velocity from 141 animal species, tested for structural clustering of sperm morphology and then compared the model predictions across all morphologically similar sperm clusters. Within four of five morphological clusters of sperm, we did not find a significant positive relationship between total sperm length and velocity. Instead, in four morphological sperm clusters we found evidence for the Constant Speed model, which predicts that power output is determined by the flagellum and so is proportional to flagellum length. Our results show the relationship between sperm morphology (size, width) and swimming speed is complex and that traditional models do not capture the biophysical interactions involved. Future work therefore needs to incorporate not only a better understanding of how sperm operate in the microfluid environment, but also the importance of fertilising environment, i.e., internal and external fertilisers. The microenvironment in which sperm operate is of critical importance in shaping the relationship between sperm length and form and sperm swimming speed.}, } @article {pmid36351992, year = {2022}, author = {Abdizadeh, GR and Farokhinejad, M and Ghasemloo, S}, title = {Numerical investigation on the aerodynamic efficiency of bio-inspired corrugated and cambered airfoils in ground effect.}, journal = {Scientific reports}, volume = {12}, number = {1}, pages = {19117}, pmid = {36351992}, issn = {2045-2322}, mesh = {Animals ; *Flight, Animal ; *Wings, Animal ; Models, Biological ; Computer Simulation ; }, abstract = {This research numerically investigates the flapping motion effect on the flow around two subsonic airfoils near a ground wall. Thus far, the aerodynamic efficiency of the dragonfly-inspired flapping airfoil has not been challenged by an asymmetric cambered airfoil considering the ground effect phenomenon, especially in the MAV flight range. The analysis is carried out on the basis of an unsteady Reynolds-averaged Navier-stokes (URANS) simulation, whereby the Transition SST turbulence model simulates the flow characteristics. Dragonfly-inspired and NACA4412 airfoils are selected in this research to assess the geometry effect on aerodynamic efficiency. Moreover, the impacts of Reynolds number (Re), Strouhal number (St), and average ground clearance of the flapping airfoil are investigated. The results indicate a direct relationship between the airfoil's aerodynamic performance ([Formula: see text]/[Formula: see text]) and the ground effect. The [Formula: see text]/[Formula: see text] increases by reducing the airfoil and ground distance, especially at [Formula: see text]. At [Formula: see text], by increasing the St from 0.2 to 0.6, the values of [Formula: see text]/[Formula: see text] decrease from 10.34 to 2.1 and 3.22 to 1.8 for NACA4412 and dragonfly airfoils, respectively. As a result, the [Formula: see text]/[Formula: see text] of the NACA4412 airfoil is better than that of the dragonfly airfoil, especially at low oscillation frequency. The efficiency difference between the two airfoils at St=0.6 is approximately 14%, indicating that the [Formula: see text]/[Formula: see text] difference decreases substantially with increasing frequency. For [Formula: see text], the results show the dragonfly airfoil to have better [Formula: see text]/[Formula: see text] in all frequencies than the NACA4412 airfoil.}, } @article {pmid36340085, year = {2022}, author = {Dang, J and Duan, X and Tian, S}, title = {Wall Effects for Spheroidal Particle in Confined Bingham Plastic Fluids.}, journal = {ACS omega}, volume = {7}, number = {43}, pages = {38717-38727}, doi = {10.1021/acsomega.2c04357}, pmid = {36340085}, issn = {2470-1343}, abstract = {The wall effects on the sedimentation motion of a single spheroidal particle in cylindrical tubes filled with Bingham plastic fluid are investigated with the fixed computational domain using the Computational Fluid Dynamic (CFD) model in steady-state mode. The CFD model is validated with literature in both bounded and unbounded mediums. The rheological model of the Bingham plastic fluid is regularized with a smoothly varying viscosity. The retardation effects of the tube wall are presented in functions of Reynolds number Re, radius ratio λ (the radius of the tube to the semiaxis of the particle normal to the flow λ = R/r), aspect ratio E (the ratio of the semiaxis of the particle along the flow to r, E = b/r), and Bingham number Bn. The simulation results demonstrate that the drag coefficient C D declines with the rise in Reynolds number. The relative contribution to drag coefficient from the pressure force increases with larger Bingham number comparing with that from the friction force. The formation and size of the recirculation wake is suppressed by the yield stress. While Bn is approaching infinity, the limiting behavior is observed in the location of yield surface and the value of yield-gravity parameter. The values of critical yield-gravity parameter are explicitly given at different values of E, showing independence with Re and λ. For the flow with Bn ≥ 100, the influence of wall can be even ignored while λ is larger than 5.}, } @article {pmid36337262, year = {2022}, author = {Rutledge, KM}, title = {Sniffing out Stingray Noses: The Functional Morphology of Batoid Olfaction.}, journal = {Integrative organismal biology (Oxford, England)}, volume = {4}, number = {1}, pages = {obac043}, pmid = {36337262}, issn = {2517-4843}, abstract = {Batoid fishes (rays, skates, sawfishes, and guitarfishes) are macrosmatic, meaning they rely on their sense of smell as one of the primary senses for survival and reproduction. Olfaction is important for long-distance tracking and navigation, predator and prey recognition, and conspecific signaling. However, the mechanisms by which batoids harness odorants is unknown. Without a direct pump-like system, it is hypothesized that batoids irrigate their nostrils via one or a combination of the following: the motion pump, buccopharyngeal pump, pressure (ex. pitot-like mechanism), or a shearing force (ex. viscous entrainment). These mechanisms rely on the size, shape, and position of the nostrils with respect to the head and to each other. Batoids are united as a group by their dorsoventrally compressed body plans, with nostrils on the ventral side of their body. This position presents several challenges for odor capture and likely limits the effectivity of the motion pump. Batoid fishes display an expansive nasal morphology, with inlet nostrils ranging from thin, vertical slits to wide, horizontal ovals to protruding, tube-like funnels, and more. In this paper, a morphometric model is developed to quantify the vast diversity in batoid nose shapes, sizes, and positions on the head in an ecological and functional framework. Specifically, swimming mode, lifestyle, habitat, and diet are examined for correlations with observed nasal morphotypes. Morphometric measurements were taken on all 4 orders present in Batoidea to broadly encompass batoid nasal diversity (Rhinopristiformes 4/5 families; Rajiformes 2/4 families; Torpediniformes 4/4 families; Myliobatiformes 8/11 families). All batoid external nasal diversity was found to be categorized into 5 major morphological groups and were termed: flush nare [circle, comma, intermediate], open nare, and protruding nare. Several morphometric traits remained significant when accounting for shared ancestry, including the position and angle of the nostril on the head, the width of the inlet hole, and the spacing of the nostrils from each other. These measurements were found to be closely correlated and statistically significant with the swimming mode of the animal. This study provides the first crucial step in understanding batoid olfaction, by understanding the diversity of the morphology of the system. Because odor capture is a strictly hydrodynamic process, it may be that factors relating more directly to the fluid dynamics (i.e., swimming mode, velocity, Reynolds number) may be more important in shaping the evolution of the diversity of batoid noses than other ecological factors like habitat and diet.}, } @article {pmid36332888, year = {2022}, author = {Saleem, T and Powell, T and Walker, W and Raju, S}, title = {Assessment of flow mechanics in the lower extremity venous system.}, journal = {Journal of vascular surgery. Venous and lymphatic disorders}, volume = {}, number = {}, pages = {}, doi = {10.1016/j.jvsv.2022.10.009}, pmid = {36332888}, issn = {2213-3348}, abstract = {BACKGROUND: Reynolds number (Re) is a dimensionless parameter that describes fluid flow mechanics. Veins are compliant and collapsible vascular conduits that can accommodate large volume changes in response to small pressure changes. However, only sparse information is available about flow parameters such as Re in the venous system.

METHODS: Bilateral duplex examination of 15 healthy volunteers (30 limbs) was performed before and after exercise (4 flights of stairs) in the veins of the lower extremity (left and right sides) and inferior vena cava. These volunteers were determined not to have any signs and symptoms of lower extremity venous disease on the basis of a focused history and physical examination.

RESULTS: Majority of the volunteers were female (73%). Mean age was 37 ± 12.8 years. Re was noted to be highest in the IVC amongst all the veins that were examined [470 (±144) pre-exercise and 589 (±205) post-exercise], p value 0.04. The association between the change in Re (pre-exercise and post-exercise) and the specific vein examined was also found to be significant for right and left external iliac veins, right and left common femoral veins, right and left profunda femoris veins, right and left femoral veins and right common iliac vein. Resistance and velocity maps for the lower extremity venous system were also created. Velocity increased while resistance decreased as we moved up the venous tree towards the right atrium.

CONCLUSION: Re increased for the majority of the lower extremity veins after exercise in the healthy volunteers. However, the critical value for turbulent flow was not reached despite exercise.}, } @article {pmid36329077, year = {2022}, author = {Roósz, A and Rónaföldi, A and Svéda, M and Veres, Z}, title = {Effect of crucible wall roughness on the laminar/turbulent flow transition of the Ga75In25 alloy stirred by a rotating magnetic field.}, journal = {Scientific reports}, volume = {12}, number = {1}, pages = {18592}, pmid = {36329077}, issn = {2045-2322}, support = {ANN 130946//Hungarian National Research, Development, and Innovation Office/ ; ANN 130946//Hungarian National Research, Development, and Innovation Office/ ; ANN 130946//Hungarian National Research, Development, and Innovation Office/ ; ANN 130946//Hungarian National Research, Development, and Innovation Office/ ; }, abstract = {The critical magnetic induction (Bcr) values of a melt flow produced by a rotating magnetic field (RMF), remaining laminar or turbulent, are essential in different solidification processes. In an earlier paper (Metall Res Technol 100: 1043-1061, 2003), we showed that Bcr depends on the crucible radius (R) and frequency of the magnetic field (f). The effect of wall roughness (WR) on Bcr was investigated in this study. Using ten different wall materials, we determined the angular frequency (ω) and Reynolds number (Re) as a function of the magnetic induction (B) and f using two different measuring methods (pressure compensation method, PCM; height measuring method, HMM). The experiments were performed at room temperature; therefore, the Ga75wt%In25wt% alloy was chosen for the experiments. Based on the measured and calculated results, a simple relationship was determined between Bcr and Re*, f, R, and WR, where the constants K1, K2, K3, and K4 depended on the physical properties of the melt and wall material:[Formula: see text].}, } @article {pmid36319372, year = {2022}, author = {Datta, R and Russell, DR and Tang, I and Clayson, T and Suttle, LG and Chittenden, JP and Lebedev, SV and Hare, JD}, title = {Time-resolved velocity and ion sound speed measurements from simultaneous bow shock imaging and inductive probe measurements.}, journal = {The Review of scientific instruments}, volume = {93}, number = {10}, pages = {103530}, doi = {10.1063/5.0098823}, pmid = {36319372}, issn = {1089-7623}, abstract = {We present a technique to measure the time-resolved velocity and ion sound speed in magnetized, supersonic high-energy-density plasmas. We place an inductive ("b-dot") probe in a supersonic pulsed-power-driven plasma flow and measure the magnetic field advected by the plasma. As the magnetic Reynolds number is large (RM > 10), the plasma flow advects a magnetic field proportional to the current at the load. This enables us to estimate the flow velocity as a function of time from the delay between the current at the load and the signal at the probe. The supersonic flow also generates a hydrodynamic bow shock around the probe, the structure of which depends on the upstream sonic Mach number. By imaging the shock around the probe with a Mach-Zehnder interferometer, we determine the upstream Mach number from the shock Mach angle, which we then use to determine the ion sound speed from the known upstream velocity. We use the sound speed to infer the value of Z̄Te, where Z̄ is the average ionization and Te is the electron temperature. We use this diagnostic to measure the time-resolved velocity and sound speed of a supersonic (MS ∼ 8), super-Alfvénic (MA ∼ 2) aluminum plasma generated during the ablation stage of an exploding wire array on the Magpie generator (1.4 MA, 250 ns). The velocity and Z̄Te measurements agree well with the optical Thompson scattering measurements reported in the literature and with 3D resistive magnetohydrodynamic simulations in GORGON.}, } @article {pmid36313190, year = {2022}, author = {Qiao, Y and Ma, Z and Onyango, C and Cheng, X and Dorfman, KD}, title = {DNA fragmentation in a steady shear flow.}, journal = {Biomicrofluidics}, volume = {16}, number = {5}, pages = {054109}, doi = {10.1063/5.0109361}, pmid = {36313190}, issn = {1932-1058}, abstract = {We have determined the susceptibility of T4 DNA (166 kilobase pairs, kbp) to fragmentation under steady shear in a cone-and-plate rheometer. After shearing for at least 30 min at a shear rate of 6000 s - 1 , corresponding to a Reynolds number of O (10 3) and a Weissenberg number of O (10 3) , 97.9 ± 1.3 % of the sample is broken into a polydisperse mixture with a number-averaged molecular weight of 62.6 ± 3.2 kbp and a polydispersity index of 1.29 ± 0.03 , as measured by pulsed-field gel electrophoresis (with a 95% confidence interval). The molecular weight distributions observed here from a shear flow are similar to those produced by a (dominantly extensional) sink flow of DNA and are qualitatively different than the midpoint scission observed in simple extensional flow. Given the inability of shear flow to produce a sharp coil-stretch transition, the data presented here support a model where polymers can be fragmented in flow without complete extension. These results further indicate that DNA fragmentation by shear is unlikely to be a significant issue in microfluidic devices, and anomalous molecular weight observations in experiments are due to DNA processing prior to observation in the device.}, } @article {pmid36301473, year = {2023}, author = {Bryan, MT}, title = {Assessing the Challenges of Nanotechnology-Driven Targeted Therapies: Development of Magnetically Directed Vectors for Targeted Cancer Therapies and Beyond.}, journal = {Methods in molecular biology (Clifton, N.J.)}, volume = {2575}, number = {}, pages = {105-123}, pmid = {36301473}, issn = {1940-6029}, abstract = {Targeted delivery, in which therapeutic agents are preferentially concentrated at the diseased site, has the potential to improve therapeutic outcomes by minimizing off-target interactions in healthy tissue. Both passive and active methods of targeting delivery have been proposed, often with particular emphasis on cancer treatment. Passive methods rely on the overexpression of a biomarker in diseased tissue that can then be used to target the therapy. Active techniques involve physically guiding therapeutic agents toward the target region. Since the motion of magnetic particles can be remotely controlled by external magnetic fields, magnetic technologies have the potential to drive and hold drugs or other cargo at the required therapeutic site, increasing the localized dose while minimizing overall exposure. Directed motion may be generated either by simple magnetic attraction or by causing the particles to perform swimming strokes to produce propulsion. This chapter will compare the different strategies using magnetic nanotechnology to produce directed motion compatible with that required for targeted cargo delivery and magnetically assisted therapies and assess their potential to meet the challenges of operating within the human body.}, } @article {pmid36296816, year = {2022}, author = {Beck, J and Palmer, M and Inman, K and Wohld, J and Cummings, M and Fulmer, R and Scherer, B and Vafaei, S}, title = {Heat Transfer Enhancement in the Microscale: Optimization of Fluid Flow.}, journal = {Nanomaterials (Basel, Switzerland)}, volume = {12}, number = {20}, pages = {}, doi = {10.3390/nano12203628}, pmid = {36296816}, issn = {2079-4991}, abstract = {The focus of this paper is to investigate the effects of the addition of a connector between two serial microchannels. The idea of adding connector at the inlet of microchannels to enhance the random motion of molecules or nanoparticles in low Reynolds numbers was developed in our research group for the first time. It was experimentally determined that the shape of a connector between two microchannels has a significant impact on the enhancement of the random motion of molecules or nanoparticles. Consequently, the heat transfer coefficient is improved inside the second microchannel. The connector is large enough to refresh the memory of the fluid before entering the second channel, causing a higher maximum heat transfer coefficient in the second channel. It was also observed that the heat transfer coefficient can be increased at the end of the channel when the outlet temperature is relatively high. This may be explained by the fact that as temperature increases, the fluid viscosity tends to decrease, which generally drives an increase in the local random motion of base fluid molecules and nanoparticles. This causes an increase in the microchannel heat transfer coefficient. It was found that the addition of nanoparticles significantly modified the impact of the connector on the microchannel heat transfer coefficient. In addition, the effects of changing the Reynolds number and the shape of the connector were investigated through use of computational fluid dynamics (CFD) calculations. It was found that both factors have an important impact on the variation of velocity and enhancement of random motion of molecules and consequently significantly affect the heat transfer coefficient.}, } @article {pmid36296785, year = {2022}, author = {Chang, Q and Fu, Z and Zhang, S and Wang, M and Pan, X}, title = {Experimental Investigation of Reynolds Number and Spring Stiffness Effects on Vortex-Induced Vibration Driven Wind Energy Harvesting Triboelectric Nanogenerator.}, journal = {Nanomaterials (Basel, Switzerland)}, volume = {12}, number = {20}, pages = {}, doi = {10.3390/nano12203595}, pmid = {36296785}, issn = {2079-4991}, support = {51979045//National Natural Science Foundation of China/ ; }, abstract = {Vortex-induced vibration (VIV) is a process that wind energy converts to the mechanical energy of the bluff body. Enhancing VIV to harvest wind energy is a promising method to power wireless sensor nodes in the Internet of Things. In this work, a VIV-driven square cylinder triboelectric nanogenerator (SC-TENG) is proposed to harvest broadband wind energy. The vibration characteristic and output performance are studied experimentally to investigate the effect of the natural frequency by using five different springs in a wide range of stiffnesses (27 N/m

PURPOSE: To evaluate the effect of baseline blood flow rates and injection conditions on the extent of contrast reflux. To estimate arterial flow rates based on measurement of contrast reflux length.

MATERIALS AND METHODS: Iodinated contrast was injected into an idealized tube as well as a physiologically accurate model of the cervico-cerebral vasculature. A total of 194 high-speed angiograms were acquired under varying 'blood' flow rates and injection conditions (catheter size, injection rate, injection time). The length of contrast reflux was compared to the input variables and to dimensionless fluid dynamics parameters at the catheter-tip. Arterial blood flow rates were estimated using contrast reflux length as well as a traditional transit-time method and compared to measured flow rates.

RESULTS: Contrast reflux lengths were significantly affected by contrast injection rate (p<0.0001), baseline blood flow rate (p = 0.0004), and catheter size (p = 0.04), but not by contrast injection time (p = 0.4). Reflux lengths were found to be correlated to dimensionless fluid dynamics parameters by an exponential function (R2 = 0.6 to 0.99). When considering the entire dataset in unison, flow estimation errors with the reflux-length method (39±33%) were significantly higher (p = 0.003) than the transit-time method (33±36%). However, when sub-grouped by catheter, the error with the reflux-length method was substantially reduced and was significantly lower (14±14%, p<0.0001) than the transit-time method.

CONCLUSION: Results show correlations between contrast reflux length and baseline hemodynamic parameters that have not been reported previously. Clinically relevant blood flow rate estimation is feasible by simple measurement of reflux length. In vivo and clinical studies are required to confirm these correlations and to refine the methodology of estimating blood flow by reflux. This article is protected by copyright. All rights reserved.}, } @article {pmid36014668, year = {2022}, author = {Shi, R and Lin, J and Yang, H}, title = {Particle Distribution and Heat Transfer of SiO2/Water Nanofluid in the Turbulent Tube Flow.}, journal = {Nanomaterials (Basel, Switzerland)}, volume = {12}, number = {16}, pages = {}, doi = {10.3390/nano12162803}, pmid = {36014668}, issn = {2079-4991}, support = {12132015//National Natural Science Foundation of China/ ; }, abstract = {In order to clarify the effect of particle coagulation on the heat transfer properties, the governing equations of nanofluid together with the equation for nanoparticles in the SiO2/water nanofluid flowing through a turbulent tube are solved numerically in the range of Reynolds number 3000 ≤ Re ≤ 16,000 and particle volume fraction 0.005 ≤ φ ≤ 0.04. Some results are validated by comparing with the experimental results. The effect of particle convection, diffusion, and coagulation on the pressure drop ∆P, particle distribution, and heat transfer of nanofluid are analyzed. The main innovation is that it gives the effect of particle coagulation on the pressure drop, particle distribution, and heat transfer. The results showed that ∆P increases with the increase in Re and φ. When inlet velocity is small, the increase in ∆P caused by adding particles is relatively large, and ∆P increases most obviously compared with the case of pure water when the inlet velocity is 0.589 m/s and φ is 0.004. Particle number concentration M0 decreases along the flow direction, and M0 near the wall is decreased to the original 2% and decreased by about 90% in the central area. M0 increases with increasing Re but with decreasing φ, and basically presents a uniform distribution in the core area of the tube. The geometric mean diameter of particle GMD increases with increasing φ, but with decreasing Re. GMD is the minimum in the inlet area, and gradually increases along the flow direction. The geometric standard deviation of particle diameter GSD increases sharply at the inlet and decreases in the inlet area, remains almost unchanged in the whole tube, and finally decreases rapidly again at the outlet. The effects of Re and φ on the variation in GSD along the flow direction are insignificant. The values of convective heat transfer coefficient h and Nusselt number Nu are larger for nanofluids than that for pure water. h and Nu increase with the increase in Re and φ. Interestingly, the variation in φ from 0.005 to 0.04 has little effect on h and Nu.}, } @article {pmid36014601, year = {2022}, author = {Akram, S and Athar, M and Saeed, K and Razia, A and Alghamdi, M and Muhammad, T}, title = {Impact of Partial Slip on Double Diffusion Convection of Sisko Nanofluids in Asymmetric Channel with Peristaltic Propulsion and Inclined Magnetic Field.}, journal = {Nanomaterials (Basel, Switzerland)}, volume = {12}, number = {16}, pages = {}, doi = {10.3390/nano12162736}, pmid = {36014601}, issn = {2079-4991}, abstract = {The current article discusses the outcomes of the double diffusion convection of peristaltic transport in Sisko nanofluids along an asymmetric channel having an inclined magnetic field. Consideration is given to the Sisko fluid model, which can forecast both Newtonian and non-Newtonian fluid properties. Lubricating greases are the best examples of Sisko fluids. Experimental research shows that most realistic fluids, including human blood, paint, dirt, and other substances, correspond to Sisko's proposed definition of viscosity. Mathematical modelling is considered to explain the flow behavior. The simpler non-linear PEDs are deduced by using an elongated wavelength and a minimal Reynolds number. The expression is also numerically calculated. The impacts of the physical variables on the quantities of flow are plotted graphically as well as numerically. The results reveal that there is a remarkable increase in the concentration, temperature, and nanoparticle fraction with the rise in the Dufour and thermophoresis variables.}, } @article {pmid36001259, year = {2022}, author = {Canli, E and Kucuksariyildiz, H and Carman, K}, title = {Impact assessment of new generation high-speed agricultural tractor aerodynamics on transportation fuel consumption and related phenomena.}, journal = {Environmental science and pollution research international}, volume = {}, number = {}, pages = {}, pmid = {36001259}, issn = {1614-7499}, abstract = {New generation agricultural tractors contribute to transportation by increased travel speeds. There is not any available aerodynamic data on the authentic agricultural tractor form. On-road transportation by tractors is between 8 and 30% of their operational time. In this work, two agricultural tractors are modelled via computational fluid dynamics for nine different speeds to determine aerodynamic resistances. Constant speed travel scenarios are analyzed. Corresponding speeds are 5 and 10 to 80 km/h with 10 km/h increments. Reynolds number changes between 1.6 × 105 and 2.98 × 106. The characteristic lengths are taken as the square root of the streamwise projected area of the tractor geometries. Aerodynamic forces exerted on the tractors change between 3 and 746 N. The calculated drag coefficients are found as independent from Reynolds number and are 0.6 and 0.78 for the two different types of driver compartments. The approximated aerodynamic related fuel consumptions for 1-h changes between 0.002 and 8.28 lt/s which correspond to 0.001 to 5.76 kg/s carbon emission. A potential improvement in decreasing aerodynamic resistance about 20% is discussed by spatial data. Since the conducted work is being regarded as the first instance in the literature, it is estimated that several consecutive reports will be triggered.}, } @article {pmid35999194, year = {2022}, author = {Nan, K and Shi, Y and Zhao, T and Tang, X and Zhu, Y and Wang, K and Bai, J and Zhao, W}, title = {Mixing and Flow Transition in an Optimized Electrokinetic Turbulent Micromixer.}, journal = {Analytical chemistry}, volume = {}, number = {}, pages = {}, doi = {10.1021/acs.analchem.2c02960}, pmid = {35999194}, issn = {1520-6882}, abstract = {Micromixer is a key element in a lab on a chip for broad applications in the analysis and measurement of chemistry and engineering. Previous investigations reported that electrokinetic (EK) turbulence could be realized in a "Y" type micromixer with a cross-sectional dimension of 100 μm order. Although the ultrafast turbulent mixing can be generated at a bulk flow Reynolds number on the order of unity, the micromixer has not been optimized. In this investigation, we systematically investigated the influence of electric field intensity, AC frequency, electric conductivity ratio, and channel width at the entrance on the mixing effect and transition electric Rayleigh number in the "Y" type electrokinetic turbulent micromixer. It is found that the optimal mixing is realized in a 350 μm wide micromixer, under 100 kHz and 1.14 × 105 V/m AC electric field, with an electric conductivity ratio of 1:3000. Under these conditions, a degree of mixedness of 0.93 can be achieved at 84 μm from the entrance and 100 ms. A further investigation of the critical electric field and the critical electric Rayleigh number indicates that the most unstable condition of EK flow instability is inconsistent with that of the optimal mixing in EK turbulence. To predict the evolution of EK flow under high Raσ and guide the design of EK turbulent micromixers, it is necessary to apply a computational turbulence model instead of linear instability analysis.}, } @article {pmid35990482, year = {2022}, author = {Mondal, T and Hnaien, N and Ajmi, M and Ghachem, K and Kolsi, L}, title = {CFD Investigation of Thermal Characteristics for a Dual Jet with a Parallel Co-flow.}, journal = {ACS omega}, volume = {7}, number = {32}, pages = {27864-27875}, doi = {10.1021/acsomega.2c00609}, pmid = {35990482}, issn = {2470-1343}, abstract = {A combined turbulent wall jet and offset jet (also known as the dual jet) with and without the presence of a parallel co-flow stream is studied. The standard k-ω turbulence model is used to predict the turbulent flow. The study focuses on the effects of the co-flow velocity (CFV) on the heat-transfer characteristics of the dual jet flow with the bottom wall maintained at a constant wall temperature. The CFV is varied up to 40% of the jet inlet velocity, and the height of the offset jet is varied from 5 to 11 times the jet width with the inlet Reynolds number taken as 15,000. The heat-transfer results reveal that the local Nusselt number (Nu x) along the bottom wall exhibits a peak at the immediate downstream of the nozzle exit, followed by a continuous decay in the rest of the converging region before showing a small rise for a short streamwise distance in the merging region. Further downstream, in the combined region, Nu x gradually decreases with the downstream distance. Except the merging region, no influence of co-flow is observed in the other two flow zones (converging and combined regions). In the merging region, for a given offset ratio (OR), Nu x remains nearly constant for a certain axial distance, and it decreases as the CFV increases. As a result of the increase in the CFV, the average Nusselt number decreases, indicating a reduction in overall convective heat transfer for higher values of the CFV. A regression analysis among the average Nusselt number (), CFV, and OR results in a correlation function in the form of within the range OR = 5-11 and CFV = 0-40%.}, } @article {pmid35965667, year = {2022}, author = {Wüthrich, D and Shi, R and Chanson, H}, title = {Hydraulic jumps with low inflow Froude numbers: air-water surface patterns and transverse distributions of two-phase flow properties.}, journal = {Environmental fluid mechanics (Dordrecht, Netherlands : 2001)}, volume = {22}, number = {4}, pages = {789-818}, doi = {10.1007/s10652-022-09854-5}, pmid = {35965667}, issn = {1567-7419}, abstract = {Abstract: Hydraulic jumps are commonly employed as energy dissipators to guarantee long-term operation of hydraulic structures. A comprehensive and in-depth understanding of their main features is therefore fundamental. In this context, the current study focused on hydraulic jumps with low Froude numbers, i.e. Fr1 = 2.1 and 2.4, at relatively high Reynolds number: Re ~2 × 105. Experimental tests employed a combination of dual-tip phase-detection probes and ultra-high-speed video camera to provide a comprehensive characterisation of the main air-water flow properties of the hydraulic jump, including surface flow features, void fraction, bubble count rate and interfacial velocities. The current research also focused on the transverse distributions of air-water flow properties, i.e. across the channel width, with the results revealing lower values of void fraction and bubble count rate next to the sidewalls compared to the channel centreline data. Such a spatial variability in the transverse direction questions whether data near the side walls may be truly representative of the behaviour in the bulk of the flow, raising the issue of sidewall effects in image-based techniques. Overall, these findings provide new information to both researchers and practitioners for a better understanding of the physical processes inside the hydraulic jump with low Froude numbers, leading to an optimised design of hydraulic structures.

Article Highlights: Experimental investigation of air-water flow properties in hydraulic jumps with low Froude numbersDetailed description of the main air-water surface features on the breaking rollerTransversal distribution of the air-water flow properties across the channel width and comparison between centreline and sidewall.}, } @article {pmid35958096, year = {2022}, author = {Mohanty, RK and Setia, N and Khurana, G and Manchanda, G}, title = {High precision compact numerical approximation in exponential form for the system of 2D quasilinear elliptic BVPs on a discrete irrational region.}, journal = {MethodsX}, volume = {9}, number = {}, pages = {101790}, doi = {10.1016/j.mex.2022.101790}, pmid = {35958096}, issn = {2215-0161}, abstract = {This article presents a new approximation of order four in exponential form for two-dimensional (2D) quasilinear partial differential equation (PDE) of elliptic form with solution domain being irrational. It is further extended for application to a system of quasilinear elliptic PDEs with Dirichlet boundary conditions (DBCs). The main highlights of the method framed in this article are as under:•It uses a 9-point stencil with unequal mesh to approach the solution. The error analysis is discussed to authenticate the order of convergence of the proposed numerical approximation.•Various validating problems, for instance the Burgers' equation, Poisson equation in cylindrical coordinates, Navier-Stokes (NS) equations in rectangular and cylindrical coordinates are solved using the proposed techniques to depict their stability. The proposed approximation produces solution free of oscillations for large values of Reynolds Number in the vicinity of a singularity.•The results of the proposed method are superior in comparison to the existing methods of [49] and [56].}, } @article {pmid35957150, year = {2022}, author = {Togun, H and Homod, RZ and Yaseen, ZM and Abed, AM and Dhabab, JM and Ibrahem, RK and Dhahbi, S and Rashidi, MM and Ahmadi, G and Yaïci, W and Mahdi, JM}, title = {Efficient Heat Transfer Augmentation in Channels with Semicircle Ribs and Hybrid Al2O3-Cu/Water Nanofluids.}, journal = {Nanomaterials (Basel, Switzerland)}, volume = {12}, number = {15}, pages = {}, doi = {10.3390/nano12152720}, pmid = {35957150}, issn = {2079-4991}, abstract = {Global technological advancements drive daily energy consumption, generating additional carbon-induced climate challenges. Modifying process parameters, optimizing design, and employing high-performance working fluids are among the techniques offered by researchers for improving the thermal efficiency of heating and cooling systems. This study investigates the heat transfer enhancement of hybrid "Al2O3-Cu/water" nanofluids flowing in a two-dimensional channel with semicircle ribs. The novelty of this research is in employing semicircle ribs combined with hybrid nanofluids in turbulent flow regimes. A computer modeling approach using a finite volume approach with k-ω shear stress transport turbulence model was used in these simulations. Six cases with varying rib step heights and pitch gaps, with Re numbers ranging from 10,000 to 25,000, were explored for various volume concentrations of hybrid nanofluids Al2O3-Cu/water (0.33%, 0.75%, 1%, and 2%). The simulation results showed that the presence of ribs enhanced the heat transfer in the passage. The Nusselt number increased when the solid volume fraction of "Al2O3-Cu/water" hybrid nanofluids and the Re number increased. The Nu number reached its maximum value at a 2 percent solid volume fraction for a Reynolds number of 25,000. The local pressure coefficient also improved as the Re number and volume concentration of "Al2O3-Cu/water" hybrid nanofluids increased. The creation of recirculation zones after and before each rib was observed in the velocity and temperature contours. A higher number of ribs was also shown to result in a larger number of recirculation zones, increasing the thermal performance.}, } @article {pmid35926485, year = {2022}, author = {Bhattacharjee, A and Jabbarzadeh, M and Kararsız, G and Fu, H and Kim, M}, title = {Bacteria-Inspired Magnetically Actuated Rod-Like Soft Robot in Viscous Fluids.}, journal = {Bioinspiration & biomimetics}, volume = {}, number = {}, pages = {}, doi = {10.1088/1748-3190/ac870f}, pmid = {35926485}, issn = {1748-3190}, abstract = {This paper seeks to design, develop, and explore the locomotive dynamics and morphological adaptability of a bacteria-inspired rod-like soft robot propelled in highly viscous Newtonian fluids. The soft robots were fabricated as tapered, hollow rod-like soft scaffolds by applying a robust and economic molding technique to a polyacrylamide-based hydrogel polymer. Cylindrical micro-magnets were embedded in both ends of the soft scaffolds, which allowed bending (deformation) and actuation under a uniform rotating magnetic field. We demonstrated that the tapered rod-like soft robot in viscous Newtonian fluids could perform two types of propulsion; boundary rolling was displayed when the soft robot was located near a boundary, and swimming was displayed far away from the boundary. In addition, we performed numerical simulations to understand the swimming propulsion along the rotating axis and the way in which this propulsion is affected by the soft robot's design, rotation frequency, and fluid viscosity. Our results suggested that a simple geometrical asymmetry would enable the rod-like soft robot to perform propulsion in the low Reynolds number (Re<< 1) regime; these promising results provide essential insights into the improvements that must be made to integrate the soft robots into minimally invasivein vivoapplications.}, } @article {pmid35918493, year = {2022}, author = {Xiao, L and Liu, Q and Huang, W}, title = {Experimental research and analysis on the resistance characteristics of simulated ore bin in water.}, journal = {Scientific reports}, volume = {12}, number = {1}, pages = {13211}, pmid = {35918493}, issn = {2045-2322}, support = {51774193//National Natural Science Foundation of China/ ; ZR2017MEE025//Shandong Provincial Natural Science Foundation/ ; }, abstract = {In order to research the variation law of the longitudinal resistance coefficient of the ore bin in the marine mining system under different length-diameter ratio, external shape, additional weight and Reynolds number, a set of experimental system for testing the resistance coefficient was designed and built independently. By analyzing the experimental results, it can be seen that under the same conditions, the resistance coefficient decreases gradually with the increase of Reynolds number and finally fluctuates around a certain value. Increasing the excitation displacement will reduce the overall resistance coefficient of the ore bin. The smaller the length-diameter ratio is, the larger the corresponding force value when the vibration acceleration of the ore bin is 0, and the larger the overall resistance coefficient is. The resistance coefficient of the cylindrical section is greater than that of the rectangular shape. In order to reduce the longitudinal vibration and the transverse towing offset, the shape of the ore bin should be cylindrical in actual design and production. At low Reynolds number, the increase of added weight will increase the resistance coefficient, while at high Reynolds number, the change of added weight will not cause the change of resistance coefficient.}, } @article {pmid35912042, year = {2022}, author = {Ram, D and Bhandari, DS and Tripathi, D and Sharma, K}, title = {Propagation of H1N1 virus through saliva movement in oesophagus: a mathematical model.}, journal = {European physical journal plus}, volume = {137}, number = {7}, pages = {866}, doi = {10.1140/epjp/s13360-022-03070-2}, pmid = {35912042}, issn = {2190-5444}, abstract = {H1N1 (Swine flu) is caused by the influenza A virus which belongs to the Orthomyxoviridae family. Influenza A is very harmful to the elderly, and people with chronic respiratory disease and cardiovascular disease. Therefore, it is essential to analyse the behaviour of virus transmission through the saliva movement in oesophagus. A mathematical paradigm is developed to study the saliva movement under the applications of transverse magnetic field. Jeffrey fluid model is considered for saliva to show the viscoelastic nature. The flow nature is considered creeping and assumptions of long wavelength and low Reynolds number are adopted for analytical solutions. The Basset-Boussinesq-Oseen equation is employed to understand the propagation of H1N1 virus through saliva under the effect of applicable forces such as gravity, virtual mass, basset force, and drag forces. The suitable data for saliva, oesophagus and H1N1 virus are taken from the existing literature for simulation of the results using MATLAB software. From the graphical results, it is observed that the susceptibility to viral infections is less because the magnetic field reduces the motion of the virus particle. Further, the chances of infections in males are more as compared to females and children due to variation in viscosity of saliva. Such findings provide an understanding of the mechanics of the virus floating through the saliva (viscoelastic fluids) in the oesophagus.}, } @article {pmid35912036, year = {2022}, author = {Strazzullo, M and Girfoglio, M and Ballarin, F and Iliescu, T and Rozza, G}, title = {Consistency of the full and reduced order models for evolve-filter-relax regularization of convection-dominated, marginally-resolved flows.}, journal = {International journal for numerical methods in engineering}, volume = {123}, number = {14}, pages = {3148-3178}, doi = {10.1002/nme.6942}, pmid = {35912036}, issn = {0029-5981}, abstract = {Numerical stabilization is often used to eliminate (alleviate) the spurious oscillations generally produced by full order models (FOMs) in under-resolved or marginally-resolved simulations of convection-dominated flows. In this article, we investigate the role of numerical stabilization in reduced order models (ROMs) of marginally-resolved, convection-dominated incompressible flows. Specifically, we investigate the FOM-ROM consistency, that is, whether the numerical stabilization is beneficial both at the FOM and the ROM level. As a numerical stabilization strategy, we focus on the evolve-filter-relax (EFR) regularization algorithm, which centers around spatial filtering. To investigate the FOM-ROM consistency, we consider two ROM strategies: (i) the EFR-noEFR, in which the EFR stabilization is used at the FOM level, but not at the ROM level; and (ii) the EFR-EFR, in which the EFR stabilization is used both at the FOM and at the ROM level. We compare the EFR-noEFR with the EFR-EFR in the numerical simulation of a 2D incompressible flow past a circular cylinder in the convection-dominated, marginally-resolved regime. We also perform model reduction with respect to both time and Reynolds number. Our numerical investigation shows that the EFR-EFR is more accurate than the EFR-noEFR, which suggests that FOM-ROM consistency is beneficial in convection-dominated, marginally-resolved flows.}, } @article {pmid35905362, year = {2022}, author = {Wang, X and Shih, HY and Goldenfeld, N}, title = {Stochastic Model for Quasi-One-Dimensional Transitional Turbulence with Streamwise Shear Interactions.}, journal = {Physical review letters}, volume = {129}, number = {3}, pages = {034501}, doi = {10.1103/PhysRevLett.129.034501}, pmid = {35905362}, issn = {1079-7114}, abstract = {The transition to turbulence in wall-bounded shear flows is typically subcritical, with a poorly understood interplay between spatial fluctuations, pattern formation, and stochasticity near the critical Reynolds number. Here, we present a spatially extended stochastic minimal model for the energy budget in transitional pipe flow, which successfully recapitulates the way localized patches of turbulence (puffs) decay, split, and grow, respectively, as the Reynolds number increases through the laminar-turbulent transition. Our approach takes into account the flow geometry, as we demonstrate by extending the model to quasi-one-dimensional Taylor-Couette flow, reproducing the observed directed percolation pattern of turbulent patches in space and time.}, } @article {pmid35899947, year = {2022}, author = {Godeau, AL and Leoni, M and Comelles, J and Guyomar, T and Lieb, M and Delanoë-Ayari, H and Ott, A and Harlepp, S and Sens, P and Riveline, D}, title = {3D single cell migration driven by temporal correlation between oscillating force dipoles.}, journal = {eLife}, volume = {11}, number = {}, pages = {}, doi = {10.7554/eLife.71032}, pmid = {35899947}, issn = {2050-084X}, support = {CDFA-01-13//Deutsch-Französische Hochschule/ ; ANR-10-IDEX-0002-02//Agence Nationale de la Recherche/ ; ANR-10-LBX-0038//Agence Nationale de la Recherche/ ; ANR-10-IDEX-0001-02//Agence Nationale de la Recherche/ ; SFB 1027//Deutsche Forschungsgemeinschaft/ ; }, abstract = {Directional cell locomotion requires symmetry breaking between the front and rear of the cell. In some cells, symmetry breaking manifests itself in a directional flow of actin from the front to the rear of the cell. Many cells, especially in physiological 3D matrices do not show such coherent actin dynamics and present seemingly competing protrusion/retraction dynamics at their front and back. How symmetry breaking manifests itself for such cells is therefore elusive. We take inspiration from the scallop theorem proposed by Purcell for micro-swimmers in Newtonian fluids: self-propelled objects undergoing persistent motion at low Reynolds number must follow a cycle of shape changes that breaks temporal symmetry. We report similar observations for cells crawling in 3D. We quantified cell motion using a combination of 3D live cell imaging, visualization of the matrix displacement and a minimal model with multipolar expansion. We show that our cells embedded in a 3D matrix form myosin-driven force dipoles at both sides of the nucleus, that locally and periodically pinch the matrix. The existence of a phase shift between the two dipoles is required for directed cell motion which manifests itself as cycles with finite area in the dipole-quadrupole diagram, a formal equivalence to the Purcell cycle. We confirm this mechanism by triggering local dipolar contractions with a laser. This leads to directed motion. Our study reveals that these cells control their motility by synchronizing dipolar forces distributed at front and back. This result opens new strategies to externally control cell motion as well as for the design of micro-crawlers.}, } @article {pmid35896094, year = {2022}, author = {Zhang, JD and Sung, HJ and Huang, WX}, title = {Hydrodynamic interaction of dorsal fin and caudal fin in tuna swimming.}, journal = {Bioinspiration & biomimetics}, volume = {}, number = {}, pages = {}, doi = {10.1088/1748-3190/ac84b8}, pmid = {35896094}, issn = {1748-3190}, abstract = {Tuna, which are known for high-performance swimming, possess a large crescent dorsal fin (DF) and caudal fin (CF) that differ from those of other fishes. The hydrodynamic interaction between the DF and CF in tuna, which are represented by two tandem threedimensional (3D) flapping plates, is numerically explored in the present study. Hydrodynamic properties and wake structures of the models with and without a DF are compared to investigate the effects of the DF. The thrust on the CF is substantially enhanced by the DF, whereas the force on the DF is not affected by the CF. The constructive interaction between the leading-edge vortex (LEV) on the CF and the vortices shed from the dorsal fin (DFVs) is identified from 3D wake topology and twodimensional vorticity distributions. The circulation of spanwise vorticity quantitatively reveals that the LEV on the CF is strengthened by the same-signed DFV. The effect of the flapping phase of the CF is examined. The DF-CF interaction is sensitive to the flapping phase at a short spacing, whereas a long spacing between the two fins enables a robust constructive interaction in tuna swimming. A systematic study is carried out to explore the effects of the Strouhal number (St) and the Reynolds number (Re) on the interaction of the fins. The enhancement of thrust due to the DF is diminished at St = 0.63, whereas the Re does not substantially influence the DF-CF constructive interaction.}, } @article {pmid35892036, year = {2022}, author = {Mane, NS and Puri, DB and Mane, S and Hemadri, V and Banerjee, A and Tripathi, S}, title = {Separation of motile human sperms in a T-shaped sealed microchannel.}, journal = {Biomedical engineering letters}, volume = {12}, number = {3}, pages = {331-342}, doi = {10.1007/s13534-022-00229-9}, pmid = {35892036}, issn = {2093-985X}, abstract = {Microfluidic methods act as an effective motile sperm separation technique used in infertility treatments. This work presents a standalone microfluidic device to separate motile sperm cells from non-motile sperm cells and debris. The separation mechanism is based on the centrifugal force acting on sperms and the ability of progressive motile sperms to swim upstream. The separation of motile sperm is carried out using a simple T-shaped microchannel which constitutes three reservoirs: one inlet and two outlets. Herein, one of the outlets is kept sealed. The sealed channel leads to a high-velocity gradient and a rheotaxis zone at the T junction resulting in the separation of motile sperms. Separated sperms are isolated in a sealed channel with a low Reynolds number flow so that sperms cannot have a net displacement, which ensures that the sperms do not re-enter the fluid flow. CFD simulation is conducted to study the flow fields inside the channel and experimental investigation is carried to observe the separation behaviour of sperms. The reported device provides 100% sperm separation efficiency and ensures the entrapment of sperm cells for a longer period. A modified colorimetric nitroblue tetrazolium test conducted on separated sperm cells shows that there is only a marginal increase in superoxide (O2 -) production, proving normal sperm integrity. This device offers an effective and safe alternative to conventional sperm sorting methods.

Supplementary Information: The online version contains supplementary material available at 10.1007/s13534-022-00229-9.}, } @article {pmid35889690, year = {2022}, author = {Ghachem, K and Selimefendigil, F and Alshammari, BM and Maatki, C and Kolsi, L}, title = {Coupled Effects of Using Magnetic Field, Rotation and Wavy Porous Layer on the Forced Convection of Hybrid Nanoliquid Flow over 3D-Backward Facing Step.}, journal = {Nanomaterials (Basel, Switzerland)}, volume = {12}, number = {14}, pages = {}, doi = {10.3390/nano12142466}, pmid = {35889690}, issn = {2079-4991}, support = {PNURSP2022R41//Princess Nourah bint Abdulrahman University/ ; }, abstract = {In the present study, the effects of using a corrugated porous layer on the forced convection of a hybrid nanofluid flow over a 3D backward facing step are analyzed under the coupled effects of magnetic field and surface rotation. The thermal analysis is conducted for different values of the Reynolds number (Re between 100 and 500), the rotational Reynolds number (Rew between 0 and 2000), the Hartmann number (Ha between 0 and 15), the permeability of the porous layer (the Darcy number, Da between 10-5 and 10-2) and the amplitude (ax between 0.01 ap and 0.7 ap) and wave number (N between 1 and 16) of the porous layer corrugation. When rotations are activated, the average Nusselt number (Nu) and pressure coefficient values rise, while the increment of the latter is less. The increment in the average Nu is higher for the case with a higher permeability of the layer. When the corrugation amplitude and wave number are increased, favorable impacts of the average Nu are observed, but at the same time pressure coefficients are increased. Successful thermal performance estimations are made by using a neural-based modeling approach with a four input-two output system.}, } @article {pmid35889569, year = {2022}, author = {Minea, AA and El-Maghlany, WM and Massoud, EZ}, title = {Heat Transfer Analysis of Nanocolloids Based on Zinc Oxide Nanoparticles Dispersed in PEG 400.}, journal = {Nanomaterials (Basel, Switzerland)}, volume = {12}, number = {14}, pages = {}, doi = {10.3390/nano12142344}, pmid = {35889569}, issn = {2079-4991}, abstract = {Cooling and heating are extremely important in many industrial applications, while the thermal performance of these processes generally depends on many factors, such as fluid flow rate, inlet temperature, and many more. Hence, tremendous efforts are dedicated to the investigation of several parameters to reach an efficient cooling or heating process. The interest in adding nanoparticles in regular heat transfer fluids delivered new fluids to the market, the nanofluids. In this paper, a new nanoparticle-enhanced fluid based on polyethylene glycol with ZnO nanoparticles is considered and its hydrothermal performance is investigated for HVAC applications. The thermophysical properties of PEG 400-ZnO and their variation with temperature at different nanoparticle loading are previously determined on experimental bases and here implemented in a numerical application. The numerical results are completed at Reynolds number from 200 to 2000, while the nanoparticle concentration varies from 0.5 to 5%. Results are discussed in terms of Nusselt number, friction factor, and dimensionless pressure drop ratio at different temperatures and ZnO loading in the PEG 400 base fluid. Additionally, the evaluation performance criteria (EC) are calculated and discussed. Concluding, the newly developed fluid enhances the heat transfer up to 16% with a 13% pressure drop penalty, while the performance evaluation criteria are enhanced. Plus, several correlations are developed for both Nusselt number and friction factor as a function of relevant operating conditions.}, } @article {pmid35888927, year = {2022}, author = {Wang, Y and Yin, Z and Bao, F and Shen, J}, title = {CFD-DEM Coupling Model for Deposition Process Analysis of Ultrafine Particles in a Micro Impinging Flow Field.}, journal = {Micromachines}, volume = {13}, number = {7}, pages = {}, doi = {10.3390/mi13071110}, pmid = {35888927}, issn = {2072-666X}, abstract = {Gas with ultrafine particle impaction on a solid surface is a unique case of curvilinear motion that can be widely used for the devices of surface coatings or instruments for particle size measurement. In this work, the Eulerian-Lagrangian method was applied to calculate the motion of microparticles in a micro impinging flow field with consideration of the interactions between particle to particle, particle to wall, and particle to fluid. The coupling computational fluid dynamics (CFD) with the discrete element method (DEM) was employed to investigate the different deposition patterns of microparticles. The vortex structure and two types of particle deposits ("halo" and "ring") have been discussed. The particle deposition characteristics are affected both by the flow Reynolds number (Re) and Stokes number (stk). Moreover, two particle deposition patterns have been categorized in terms of Re and stk. Finally, the characteristics and mechanism of particle deposits have been analyzed using the particle inertia, the process of impinging (particle rebound or no rebound), vortical structures, and the kinetic energy conversion in two-phase flow, etc.}, } @article {pmid35888885, year = {2022}, author = {Zhou, Y and Dai, L and Jiao, N}, title = {Review of Bubble Applications in Microrobotics: Propulsion, Manipulation, and Assembly.}, journal = {Micromachines}, volume = {13}, number = {7}, pages = {}, doi = {10.3390/mi13071068}, pmid = {35888885}, issn = {2072-666X}, support = {Nos. 62127811, 91748212, 61821005//National Natural Science Foundation of China/ ; }, abstract = {In recent years, microbubbles have been widely used in the field of microrobots due to their unique properties. Microbubbles can be easily produced and used as power sources or tools of microrobots, and the bubbles can even serve as microrobots themselves. As a power source, bubbles can propel microrobots to swim in liquid under low-Reynolds-number conditions. As a manipulation tool, microbubbles can act as the micromanipulators of microrobots, allowing them to operate upon particles, cells, and organisms. As a microrobot, microbubbles can operate and assemble complex microparts in two- or three-dimensional spaces. This review provides a comprehensive overview of bubble applications in microrobotics including propulsion, micromanipulation, and microassembly. First, we introduce the diverse bubble generation and control methods. Then, we review and discuss how bubbles can play a role in microrobotics via three functions: propulsion, manipulation, and assembly. Finally, by highlighting the advantages and current challenges of this progress, we discuss the prospects of microbubbles in microrobotics.}, } @article {pmid35888870, year = {2022}, author = {Juraeva, M and Kang, DJ}, title = {Mixing Enhancement of a Passive Micromixer with Submerged Structures.}, journal = {Micromachines}, volume = {13}, number = {7}, pages = {}, doi = {10.3390/mi13071050}, pmid = {35888870}, issn = {2072-666X}, support = {BOKUK2022//BOKUK/ ; }, abstract = {A passive micromixer combined with two different mixing units was designed by submerging planar structures, and its mixing performance was simulated over a wider range of the Reynolds numbers from 0.1 to 80. The two submerged structures are a Norman window and rectangular baffles. The mixing performance was evaluated in terms of the degree of mixing (DOM) at the outlet and the required pressure load between inlet and outlet. The amount of submergence was varied from 30 μm to 70 μm, corresponding to 25% to 58% of the micromixer depth. The enhancement of mixing performance is noticeable over a wide range of the Reynolds numbers. When the Reynolds number is 10, the DOM is improved by 182% from that of no submergence case, and the required pressure load is reduced by 44%. The amount of submergence is shown to be optimized in terms of the DOM, and the optimum value is about 40 μm. This corresponds to a third of the micromixer depth. The effects of the submerged structure are most significant in the mixing regime of convection dominance from Re = 5 to 80. In a circular passage along the Norman window, one of the two Dean vortices burst into the submerged space, promoting mixing in the cross-flow direction. The submerged baffles in the semi-circular mixing units generate a vortex behind the baffles that contributes to the mixing enhancement as well as reducing the required pressure load.}, } @article {pmid35888205, year = {2022}, author = {Vatsa, A and Alam, T and Siddiqui, MIH and Ali, MA and Dobrotă, D}, title = {Performance of Microchannel Heat Sink Made of Silicon Material with the Two-Sided Wedge.}, journal = {Materials (Basel, Switzerland)}, volume = {15}, number = {14}, pages = {}, doi = {10.3390/ma15144740}, pmid = {35888205}, issn = {1996-1944}, abstract = {New designs of the microchannel with a two-sided wedge shape at the base were studied numerically. Five different wedge angles ranging from 3° to 15° were incorporated into the microchannel design. Simulation of this novel microchannel was carried out using Computational Fluid Dynamics (CFD). Three-dimensional models of the microchannel heat sink were created, discretized, and based on Navier-Stokes and energy equations; laminar numerical solutions were obtained for heat transfer and pressure drop. Flow characteristics of water as coolant in a microchannel were studied. It was observed that numerical results are in good agreement with experimental results. It was found that the Nusselt number and friction factor are significantly varied with the increase in Reynolds number. The Nusselt number varies in the following ranges of 5.963-8.521, 5.986-8.550, 6.009-8.568, 6.040-8.609, and 6.078-8.644 at 3°, 6°, 9°, 12°, and 15°, respectively. The microchannel with a wedge angle of 15° was found to be better in terms of Nusselt number and thermo-hydraulic performance. The enhancement in the Nusselt number is found as 1.017-1.036 for a wedge angle of 15°; however, friction factors do not show the perceptible values at distinct values of wedge angle. Moreover, the thermo-hydraulic performance parameters (THPP) were evaluated and found to be maximum in the range of 1.027-1.045 for a wedge angle of 15°. However, minimum THPP was found in the range of 1.005-1.0185 for a wedge angle of 3°.}, } @article {pmid35885078, year = {2022}, author = {Qi, T and Lin, J and Ouyang, Z}, title = {Hydrodynamic Behavior of Self-Propelled Particles in a Simple Shear Flow.}, journal = {Entropy (Basel, Switzerland)}, volume = {24}, number = {7}, pages = {}, doi = {10.3390/e24070854}, pmid = {35885078}, issn = {1099-4300}, support = {12132015//National Natural Science Foundation of China/ ; }, abstract = {The hydrodynamic properties of a squirmer type of self-propelled particle in a simple shear flow are investigated using the immersed boundary-lattice Boltzmann method in the range of swimming Reynolds number 0.05 ≤ Res ≤ 2.0, flow Reynolds number 40 ≤ Rep ≤ 160, blocking rate 0.2 ≤ κ ≤ 0.5. Some results are validated by comparing with available other results. The effects of Res, Rep and κ on the hydrodynamic properties of squirmer are discussed. The results show that there exist four distinct motion modes for the squirmer, i.e., horizontal mode, attractive oscillation mode, oscillation mode, and chaotic mode. Increasing Res causes the motion mode of the squirmer to change from a constant tumbling near the centerline to a stable horizontal mode, even an oscillatory or appealing oscillatory mode near the wall. Increasing the swimming intensity of squirmer under the definite Res will induce the squirmer to make periodic and stable motion at a specific distance from the wall. Increasing Rep will cause the squirmer to change from a stable swimming state to a spiral motion or continuous rotation. Increasing κ will strengthen the wall's attraction to the squirmer. Increasing swimming intensity of squirmer will modify the strength and direction of the wall's attraction to the squirmer if κ remains constant.}, } @article {pmid35879876, year = {2022}, author = {Punyaratabandhu, N and Dechadilok, P and Triampo, W and Katavetin, P}, title = {Hydrodynamic Model for Renal Microvascular Filtration: Effects of Physiological and Hemodynamic Changes on Glomerular Size-selectivity.}, journal = {Microcirculation (New York, N.Y. : 1994)}, volume = {}, number = {}, pages = {e12779}, doi = {10.1111/micc.12779}, pmid = {35879876}, issn = {1549-8719}, abstract = {OBJECTIVE: The first step in renal urine formation is ultrafiltration across the glomerular barrier. The change in its nanostructure has been associated with nephrotic syndromes. Effects of physiological and hemodynamic factor alterations associated with diabetic nephropathy (DN) on glomerular permselectivity are examined through a mathematical model employing low-Reynolds-number hydrodynamics and hindered transport theory.

METHODS: Glomerular capillaries are represented as networks of cylindrical tubes with multilayered walls. Glomerular basement membrane (GBM) is a fibrous medium with bimodal fiber sizes. Epithelial slit fiber spacing follows a lognormal distribution based on reported electron micrographs with the highest resolution. Endothelial fenestrae are filled with fibers the size of glycosaminoglycans (GAGs). Effects of fiber-macromolecule steric and hydrodynamic interactions are included. Focusing on diabetic nephropathy, the physiological and hemodynamic factors employed in the computation are those reported for healthy humans and patients with early-but-overt diabetic nephropathy. The macromolecule concentration is obtained as a finite element solution of the convection-diffusion equation.

RESULTS: Computed sieving coefficients averaged along the capillary length agree well with ficoll sieving coefficients from studies in humans for most solute radii. GBM thickening and the loss of the slit diaphragm hardly affect glomerular permselectivity. GAG volume fraction reduction in the endothelial fenestrae, however, significantly increases macromolecule filtration. Increased renal plasma flow rate (RPF), glomerular hypertension and reduction of lumen osmotic pressure cause a slight sieving coefficient decrease. These effects are amplified by an increased macromolecule size.

CONCLUSION: Our results indicate that glomerular hypertension and the reduction in the oncotic pressure decreases glomerular macromolecule filtration. Reduction of RPF and changes in the glomerular barrier structure associated with DN, however, increase the solute sieving. Damage to GAGs caused by hyperglycemia is likely to be the most prominent factor affecting glomerular size-selectivity.}, } @article {pmid35879342, year = {2022}, author = {Skotnicka-Siepsiak, A}, title = {Pressure distribution on a flat plate in the context of the phenomenon of the Coanda effect hysteresis.}, journal = {Scientific reports}, volume = {12}, number = {1}, pages = {12687}, pmid = {35879342}, issn = {2045-2322}, abstract = {As a result of the Coanda effect, a symmetrical free jet will flow as an asymmetrical wall jet. At the same time, at the obstacle along which the flow is observed, the wall jet generates pressure distribution. In this study, the obstacle located at the diffuser outlet is a flat plate with a variable inclination angle. The article presents results of the study on pressure distributions on a flat plate with a variable angle of inclination. In the experiment, the Reynolds number ranged from 16,192 to 42,240. A fixed geometry diffuser (Witoszyński nozzle) with a height of 0.60 m, width of 0.02 m and outlet velocity of 11.33-29.57 m/s was used. A plate with a length of 1.00 m and a variable inclination angle was installed at the diffuser outlet. What is new, however, is that the presented results of the experimental research include the influence of the Coanda effect hysteresis on the pressure distribution on the plate. The article shows how pressure distributions change on the plate depending on whether the initial angle of inclination was 0° and was increased gradually in the course of the experiment until a detachment of the jet flowing from the plate was observed, or the initial angle of inclination was close to 90° in the primal state and as the angle of the plate inclination was decreased, the jet flowing towards the plate reached the state of attachment to the plate surface. The study demonstrated that for a turbulent jet, pressure distribution on a flat plate is determined not only by the plate's inclination angle, but also by the direction of its rotation.}, } @article {pmid35863190, year = {2022}, author = {Hatte, S and Pitchumani, R}, title = {Novel nonwetting solid-infused surfaces for superior fouling mitigation.}, journal = {Journal of colloid and interface science}, volume = {627}, number = {}, pages = {308-319}, doi = {10.1016/j.jcis.2022.06.155}, pmid = {35863190}, issn = {1095-7103}, abstract = {Fouling is a ubiquitous issue in several environmental and energy applications. Here we introduce novel nonwetting solid-infused surfaces (SIS) with superior anti-fouling characteristics that are durable than conventional nonwetting surfaces in a dynamic flow environment. A systematic study is presented to elucidate the fouling mitigation performance of SIS in comparison to lubricant-infused surface (LIS) and conventional smooth surface. Copper tubes with SIS, LIS or smooth inner walls are fabricated and subjected to accelerated calcium sulfate fouling in a flow fouling experimental setup. Fouling on the various surface types is quantified in terms of asymptotic fouling resistance, and the fundamental morphological differences in the interactions of the foulant and the various surface types are analyzed. Based on a systematic sweep of the parameter combinations using design of experiments and Taguchi analysis, an analytical dependence of asymptotic fouling resistance on the governing parameters namely, Reynolds number, foulant concentration and temperature is derived. The analytical model is shown to predict the asymptotic fouling resistance to within 20% accuracy with a 95% confidence. In addition, for the first time, the effects of shear durability on the fouling mitigation performance of LIS vis-à-vis SIS are studied. It is shown that the novel nonwetting SIS offers a robust option for superior fouling mitigation over LIS in the long run.}, } @article {pmid35859200, year = {2022}, author = {Pumm, AK and Engelen, W and Kopperger, E and Isensee, J and Vogt, M and Kozina, V and Kube, M and Honemann, MN and Bertosin, E and Langecker, M and Golestanian, R and Simmel, FC and Dietz, H}, title = {A DNA origami rotary ratchet motor.}, journal = {Nature}, volume = {607}, number = {7919}, pages = {492-498}, pmid = {35859200}, issn = {1476-4687}, mesh = {*DNA/chemistry ; Diffusion ; Molecular Motor Proteins/chemistry ; Motion ; *Proton-Translocating ATPases ; Thermodynamics ; }, abstract = {To impart directionality to the motions of a molecular mechanism, one must overcome the random thermal forces that are ubiquitous on such small scales and in liquid solution at ambient temperature. In equilibrium without energy supply, directional motion cannot be sustained without violating the laws of thermodynamics. Under conditions away from thermodynamic equilibrium, directional motion may be achieved within the framework of Brownian ratchets, which are diffusive mechanisms that have broken inversion symmetry1-5. Ratcheting is thought to underpin the function of many natural biological motors, such as the F1F0-ATPase6-8, and it has been demonstrated experimentally in synthetic microscale systems (for example, to our knowledge, first in ref. 3) and also in artificial molecular motors created by organic chemical synthesis9-12. DNA nanotechnology13 has yielded a variety of nanoscale mechanisms, including pivots, hinges, crank sliders and rotary systems14-17, which can adopt different configurations, for example, triggered by strand-displacement reactions18,19 or by changing environmental parameters such as pH, ionic strength, temperature, external fields and by coupling their motions to those of natural motor proteins20-26. This previous work and considering low-Reynolds-number dynamics and inherent stochasticity27,28 led us to develop a nanoscale rotary motor built from DNA origami that is driven by ratcheting and whose mechanical capabilities approach those of biological motors such as F1F0-ATPase.}, } @article {pmid35851297, year = {2022}, author = {Shahzad, H and Wang, X and Ghaffari, A and Iqbal, K and Hafeez, MB and Krawczuk, M and Wojnicz, W}, title = {Fluid structure interaction study of non-Newtonian Casson fluid in a bifurcated channel having stenosis with elastic walls.}, journal = {Scientific reports}, volume = {12}, number = {1}, pages = {12219}, pmid = {35851297}, issn = {2045-2322}, mesh = {Arteries ; Blood Flow Velocity ; Computer Simulation ; Constriction, Pathologic ; *Hemodynamics ; Humans ; *Models, Cardiovascular ; Stress, Mechanical ; }, abstract = {Fluid-structure interaction (FSI) gained a huge attention of scientists and researchers due to its applications in biomedical and mechanical engineering. One of the most important applications of FSI is to study the elastic wall behavior of stenotic arteries. Blood is the suspension of various cells characterized by shear thinning, yield stress, and viscoelastic qualities that can be assessed by using non-Newtonian models. In this study we explored non-Newtonian, incompressible Casson fluid flow in a bifurcated artery with a stenosis. The two-dimensional Casson model is used to study the hemodynamics of the flow. The walls of the artery are supposed to be elastic and the stenosis region is constructed in both walls. Suitable scales are used to transform the nonlinear differential equations into a dimensionless form. The problem is formulated and discretized using Arbitrary Lagrangian-Eulerian (ALE) approach. The finite element method (FEM) technique is used to solve the system of equations, together with appropriate boundary conditions. The analysis is carried out for the Bingham number, Hartmann number, and Reynolds number. The graphical results of pressure field, velocity profile, and load on the walls are assessed and used to study the influence of hemodynamic effects on stenotic arteries, bifurcation region, and elastic walls. This study shows that there is an increase in wall shear stresses (WSS) with increasing values of Bingham number and Hartmann number. Also, for different values of the Bingham number, the load on the upper wall is computed against the Hartmann number. The result indicate that load at the walls increases as the values of Bingham number and Hartmann number increase.}, } @article {pmid35854607, year = {2022}, author = {Bandak, D and Goldenfeld, N and Mailybaev, AA and Eyink, G}, title = {Dissipation-range fluid turbulence and thermal noise.}, journal = {Physical review. E}, volume = {105}, number = {6-2}, pages = {065113}, doi = {10.1103/PhysRevE.105.065113}, pmid = {35854607}, issn = {2470-0053}, abstract = {We revisit the issue of whether thermal fluctuations are relevant for incompressible fluid turbulence and estimate the scale at which they become important. As anticipated by Betchov in a prescient series of works more than six decades ago, this scale is about equal to the Kolmogorov length, even though that is several orders of magnitude above the mean free path. This result implies that the deterministic version of the incompressible Navier-Stokes equation is inadequate to describe the dissipation range of turbulence in molecular fluids. Within this range, the fluctuating hydrodynamics equation of Landau and Lifschitz is more appropriate. In particular, our analysis implies that both the exponentially decaying energy spectrum and the far-dissipation-range intermittency predicted by Kraichnan for deterministic Navier-Stokes will be generally replaced by Gaussian thermal equipartition at scales just below the Kolmogorov length. Stochastic shell model simulations at high Reynolds numbers verify our theoretical predictions and reveal furthermore that inertial-range intermittency can propagate deep into the dissipation range, leading to large fluctuations in the equipartition length scale. We explain the failure of previous scaling arguments for the validity of deterministic Navier-Stokes equations at any Reynolds number and we provide a mathematical interpretation and physical justification of the fluctuating Navier-Stokes equation as an "effective field theory" valid below some high-wave-number cutoff Λ, rather than as a continuum stochastic partial differential equation. At Reynolds number around a million, comparable to that in Earth's atmospheric boundary layer, the strongest turbulent excitations observed in our simulation penetrate down to a length scale of about eight microns, still two orders of magnitude greater than the mean free path of air. However, for longer observation times or for higher Reynolds numbers, more extreme turbulent events could lead to a local breakdown of fluctuating hydrodynamics.}, } @article {pmid35854520, year = {2022}, author = {Margazoglou, G and Biferale, L and Cencini, M and Gallavotti, G and Lucarini, V}, title = {Nonequilibrium ensembles for the three-dimensional Navier-Stokes equations.}, journal = {Physical review. E}, volume = {105}, number = {6-2}, pages = {065110}, doi = {10.1103/PhysRevE.105.065110}, pmid = {35854520}, issn = {2470-0053}, abstract = {At the molecular level fluid motions are, by first principles, described by time reversible laws. On the other hand, the coarse grained macroscopic evolution is suitably described by the Navier-Stokes equations, which are inherently irreversible, due to the dissipation term. Here, a reversible version of three-dimensional Navier-Stokes is studied, by introducing a fluctuating viscosity constructed in such a way that enstrophy is conserved, along the lines of the paradigm of microcanonical versus canonical treatment in equilibrium statistical mechanics. Through systematic simulations we attack two important questions: (a) What are the conditions that must be satisfied in order to have a statistical equivalence between the two nonequilibrium ensembles? (b) What is the empirical distribution of the fluctuating viscosity observed by changing the Reynolds number and the number of modes used in the discretization of the evolution equation? The latter point is important also to establish regularity conditions for the reversible equations. We find that the probability to observe negative values of the fluctuating viscosity becomes very quickly extremely small when increasing the effective Reynolds number of the flow in the fully resolved hydrodynamical regime, at difference from what was observed previously.}, } @article {pmid35854514, year = {2022}, author = {Choudhury, A and Samanta, A}, title = {Linear stability of a falling film over a heated slippery plane.}, journal = {Physical review. E}, volume = {105}, number = {6-2}, pages = {065112}, doi = {10.1103/PhysRevE.105.065112}, pmid = {35854514}, issn = {2470-0053}, abstract = {A detailed parametric study on the linear stability analysis of a three-dimensional thin liquid film flowing down a uniformly heated slippery inclined plane is carried out for disturbances of arbitrary wavenumbers, where the liquid film satisfies Newton's law of cooling at the film surface. A coupled system of boundary value problems is formulated in terms of the amplitudes of perturbation normal velocity and perturbation temperature, respectively. Analytical solution of the boundary value problems demonstrates the existence of three dominant modes, the so-called H mode, S mode, and P mode, where the S mode and P mode emerge due to the thermocapillary effect. It is found that the onset of instabilities for the H mode, S mode, and P mode reduces in the presence of wall slip and leads to a destabilizing influence. Numerical solution based on the Chebyshev spectral collocation method unveils that the finite wavenumber H-mode instability can be stabilized, but the S-mode instability and the finite wavenumber P-mode instability can be destabilized by increasing the value of the Marangoni number. On the other hand, the Biot number shows a dual role in the H-mode and S-mode instabilities. But the P-mode instability can be made stable with the increasing value of the Biot number and the decreasing values of the Marangoni number and the Prandtl number. Furthermore, the H-mode and S-mode instabilities become weaker, but the P-mode instability becomes stronger, with the increasing value of the spanwise wavenumber. In addition, the shear mode emerges in the numerical simulation when the Reynolds number is large, which can be destabilized slightly with the increasing value of the Marangoni number; however, it can be stabilized with the increasing value of the slip length and introducing the spanwise wavenumber to the infinitesimal perturbation.}, } @article {pmid35854482, year = {2022}, author = {Ishimoto, K and Moreau, C and Yasuda, K}, title = {Self-organized swimming with odd elasticity.}, journal = {Physical review. E}, volume = {105}, number = {6-1}, pages = {064603}, doi = {10.1103/PhysRevE.105.064603}, pmid = {35854482}, issn = {2470-0053}, abstract = {We theoretically investigate self-oscillating waves of an active material, which were recently introduced as a nonsymmetric part of the elastic moduli, termed odd elasticity. Using Purcell's three-link swimmer model, we reveal that an odd-elastic filament at low Reynolds number can swim in a self-organized manner and that the time-periodic dynamics are characterized by a stable limit cycle generated by elastohydrodynamic interactions. Also, we consider a noisy shape gait and derive a swimming formula for a general elastic material in the Stokes regime with its elasticity modulus being represented by a nonsymmetric matrix, demonstrating that the odd elasticity produces biased net locomotion from random noise.}, } @article {pmid35820476, year = {2022}, author = {Zhao, X and Zuo, H and Jia, G}, title = {Effects of the continuous pulsation regeneration on the soot combustion in diesel particulate filter for heavy-duty truck.}, journal = {Chemosphere}, volume = {}, number = {}, pages = {135651}, doi = {10.1016/j.chemosphere.2022.135651}, pmid = {35820476}, issn = {1879-1298}, abstract = {Continuous pulsation regeneration combustion of soot is employed for sine and cosine simulation study. Data showed that pressure uniformity of sine condition is better than that of cosine condition with the maximum pressure difference of 4353.5 Pa under the same simulation boundary conditions. The maximum regeneration temperature under cosine pressure is 46.12 K which is higher than that in sine form. Regeneration combustion reaction zone tends to be more stable laminar flow and Reynolds number of sine condition is 435.23 less than that of under cosine condition. The maximum Stanton number of cosine pressure condition is 3.67 and that of sine pressure condition is 5.15, which investigates heat transfer capacity of the sine pressure condition is better than that of the pressure of cosine form. The regeneration efficiency of inlet gradually increased from the minimum regeneration efficiency 74.18%-88.45% of sine and cosine. The soot under both pressure forms has achieved complete regeneration and the regeneration efficiency has exceeded 88% of porous medium filter body section. The soot regeneration combustion efficiency of the porous media filter section and outlet section is more sufficient under sine condition and the heat carried by the fluid can maintain the soot regeneration.}, } @article {pmid35811899, year = {2022}, author = {Sun, R and Chen, P and Li, L and Liu, Y and Zhai, X}, title = {Experimental Investigation of the Combustion Behavior of Transformer Oil Jet Flame.}, journal = {ACS omega}, volume = {7}, number = {26}, pages = {22969-22976}, doi = {10.1021/acsomega.2c03080}, pmid = {35811899}, issn = {2470-1343}, abstract = {Transformer oil jet fire is one of the most dangerous types of fires in substations. The combustion behavior of transformer oil jet fire produces uncontrollable hazards to personnel and equipment and even triggers a domino effect. However, the jet fire combustion behavior of such materials as transformer oil has not been revealed before. Investigation of the combustion behavior of transformer oil jet fire has positive implications for the prevention and control of substation fires. In this paper, KI25X transformer oil was used as fuel. A series of transformer oil jet fire experiments were conducted with variable orifice diameters (5, 10, and 15 mm) with heat release rates ranging from 200 to 659.2 kW. The results showed that the entrainment coefficient of transformer oil jet fire was greater than that of pure gas phase jet fire. The entrainment coefficient of transformer oil jet fire was 0.029. Using dimensionless theory, it was proposed that the imaginary point source was proportional to the 0.317 power of Froude number. Based on the point source model, a dimensional analysis model with Reynolds number was developed. The radiation fraction of transformer oil jet fire was proportional to the -0.133 power of Reynolds number. This study played an important role in improving the jet combustion behavior of transformer oil.}, } @article {pmid35787191, year = {2022}, author = {Jamshed, W and Safdar, R and Rehman, Z and Lashin, MMA and Ehab, M and Moussa, M and Rehman, A}, title = {Computational technique of thermal comparative examination of Cu and Au nanoparticles suspended in sodium alginate as Sutterby nanofluid via extending PTSC surface.}, journal = {Journal of applied biomaterials & functional materials}, volume = {20}, number = {}, pages = {22808000221104004}, doi = {10.1177/22808000221104004}, pmid = {35787191}, issn = {2280-8000}, abstract = {Current research underscores entropy investigation in an infiltrating mode of Sutterby nanofluid (SNF) stream past a dramatically expanding flat plate that highlights Parabolic Trough Solar Collector (PTSC). Satisfactory likeness factors are utilized to change halfway differential conditions (PDEs) to nonlinear conventional differential conditions (ODEs) along with relating limit requirements. A productive Keller-box system is locked in to achieve approximated arrangement of decreased conventional differential conditions. In the review, two sorts of nanofluids including Copper-sodium alginate (Cu-SA) and Gold-sodium alginate (Au-SA) are dissected. Results are graphically plotted as well as talked about in actual viewpoints. As indicated by key discoveries, an improvement in Brinkmann, as well as Reynolds number, brings about expanding the general framework entropy. Sutterby nanofluid boundary improves heat rate in PTSC. Additionally, Copper-sodium alginate nanofluid is detected as a superior thermal conductor than Gold-sodium alginate nanofluid. Further to that, the reported breakthroughs are beneficial to updating extremely bright lighting bulbs, heating and cooling machinery, ﬁber required to generate light, power production, numerous boilers, and other similar technologies.}, } @article {pmid35771996, year = {2022}, author = {Saro-Cortes, V and Cui, Y and Dufficy, T and Boctor, A and Flammang, BE and Wissa, AW}, title = {An Adaptable Flying Fish Robotic Model for Aero- and Hydrodynamic Experimentation.}, journal = {Integrative and comparative biology}, volume = {}, number = {}, pages = {}, doi = {10.1093/icb/icac101}, pmid = {35771996}, issn = {1557-7023}, abstract = {Flying fishes (family Exocoetidae) are known for achieving multi-modal locomotion through air and water. Previous work on understanding this animal's aerodynamic and hydrodynamic nature has been based on observations, numerical simulations, or experiments on preserved dead fish, and has focused primarily on flying pectoral fins. The first half of this paper details the design and validation of a modular flying fish inspired robotic model organism (RMO). The second half delves into a parametric aerodynamic study of flying fish pelvic fins, which to date have not been studied in-depth. Using wind tunnel experiments at a Reynolds number of 30,000, we investigated the effect of the pelvic fin geometric parameters on aerodynamic efficiency and longitudinal stability. The pelvic fin parameters investigated in this study include the pelvic fin pitch angle and its location along the body. Results show that the aerodynamic efficiency is maximized for pelvic fins located directly behind the pectoral fins and is higher for more positive pitch angles. In contrast, pitching stability is neither achievable for positive pitching angles nor pelvic fins located directly below the pectoral fin. Thus, there is a clear a trade-off between stability and lift generation, and an optimal pelvic fin configuration depends on the flying fish locomotion stage, be it gliding, taxiing, or taking off. The results garnered from the RMO experiments are insightful for understanding the physics principles governing flying fish locomotion and designing flying fish inspired aerial-aquatic vehicles.}, } @article {pmid35764779, year = {2022}, author = {Wu, YK and Liu, YP and Sun, M}, title = {Aerodynamics of two parallel bristled wings in low Reynolds number flow.}, journal = {Scientific reports}, volume = {12}, number = {1}, pages = {10928}, pmid = {35764779}, issn = {2045-2322}, support = {Nos. 11832004//National Natural Science Foundation of China/ ; Nos. 11832004//National Natural Science Foundation of China/ ; Nos. 11832004//National Natural Science Foundation of China/ ; }, abstract = {Most of the smallest flying insects use bristled wings. It was observed that during the second half of their upstroke, the left and right wings become parallel and close to each other at the back, and move upward at zero angle of attack. In this period, the wings may produce drag (negative vertical force) and side forces which tend to push two wings apart. Here we study the aerodynamic forces and flows of two simplified bristled wings experiencing such a motion, compared with the case of membrane wings (flat-plate wings), to see if there is any advantage in using the bristled wings. The method of computational fluid dynamics is used in the study. The results are as follows. In the motion of two bristled wings, the drag acting on each wing is 40% smaller than the case of a single bristled wing conducting the same motion, and only a very small side force is produced. But in the case of the flat-plate wings, although there is similar drag reduction, the side force on each wing is larger than that of the bristled wing by an order of magnitude (the underlying physical reason is discussed in the paper). Thus, if the smallest insects use membrane wings, their flight muscles need to overcome large side forces in order to maintain the intended motion for less negative lift, whereas using bristled wings do not have this problem. Therefore, the adoption of bristled wings can be beneficial during upward movement of the wings near the end of the upstroke, which may be one reason why most of the smallest insects adopt them.}, } @article {pmid35755331, year = {2022}, author = {Huang, X and Wang, Y and Wang, L and Yu, G and Wang, F}, title = {Effect of Structural Optimization of Scrubbing Cooling Rings on Vertical Falling Film Flow Characteristics.}, journal = {ACS omega}, volume = {7}, number = {24}, pages = {21291-21305}, doi = {10.1021/acsomega.2c02492}, pmid = {35755331}, issn = {2470-1343}, abstract = {In order to study the influence of the structural optimization of the scrubbing cooling ring in the scrubbing cooling chamber on the flow characteristics of the vertical falling film, the flow characteristics of the turbulent falling film in the rising section of the development region at different internal platform heights of the scrubbing cooling ring and a high Reynolds number were studied by FLUENT software. First, the correctness of the model was verified by the maximum error of simulation and experimental results of no more than 9.836%. Then, the distribution of liquid film thickness (δ), velocity (V), and turbulence intensity (I z) at 0° of the tube in the axial direction x = 0-500 mm were calculated and obtained when the platform height (H) was 0-30 mm and the liquid film Reynolds number (Re l) = 1.1541 × 104-3.4623 × 104. The results showed that δ in the entrance region increased sharply due to the "jet" effect with solid wall constraints formed by the structure of the water inlet pipe and the scrubbing cooling ring. On the contrary, the liquid film in the fully developed region showed a stable fluctuation trend due to the weakening of the "jet" effect. When H = 30 mm, the change of δ was relatively stable and the change of I z was small, indicating that this platform height is conducive to the stable and uniform distribution of the liquid film. In addition, when Re l < 1.1541 × 104, the liquid film was unstable due to the low flow rate and insufficient cohesion of the liquid film, but V increased slightly. In addition, with the increase of Re l, δ did not change significantly along the axial direction, that is, the Plateau-Rayleigh hindered the growth of δ. Finally, the empirical formula for δ applicable to Re l = 1.1541 × 104-3.4623 × 104 at the axial fixed position was fitted for the first time.}, } @article {pmid35751170, year = {2022}, author = {Ducos, S and Pugliese, S and Demolliens, M and Beraud, L and Boussard, A and Delmas, A and Agostini, S and Garcia, J and Aiello, A and Durieux, EDH}, title = {Ontogeny of swimming performance of hatchery-reared post-larvae and juvenile fish: a case of two threatened Mediterranean species.}, journal = {Journal of fish biology}, volume = {}, number = {}, pages = {}, doi = {10.1111/jfb.15144}, pmid = {35751170}, issn = {1095-8649}, abstract = {Swimming performance is a well-established key physiological parameter of fish that is highly linked to their fitness in the wild. In the context of fish restocking or restauration purposes, it therefore appears crucial to study this specific behaviour. Here, we investigated intra and interspecies differences in the swimming performance of hatchery-reared post-larvae and juveniles belonging to two Mediterranean candidate threatened species, the common dentex, Dentex dentex (Sparidae), and the brown meagre, Sciaena umbra (Sciaenidae), with body sizes ranging from 8 to 37 mm TL (from 24 to 58 days post-hatch). The swimming abilities were estimated through the calculation of their critical swimming speed (Ucrit), their relative Ucrit and their Reynolds number (Re). Two different patterns were observed between D. dentex and S. umbra, showing a different effect of ontogeny on the performance of both species. The relative Ucrit of S. umbra decreased linearly through ontogeny, whereas the relative Ucrit and Ucrit of D. dentex increased linearly through the range of sizes tested. The ontogenetic change in Ucrit of S. umbra occurred in two stages: a first stage of sharp improvement and a second stage of a slow decrease in performance. Both stages were separated by a breakpoint that coincided with the appearance of a refusal to swim behaviour that occurred shortly after the end of metamorphosis and can potentially be associated with the establishment of this species sedentary behaviour. The swimming performance of both species showed ontogenetic differences. Sciaena umbra had the highest relative performance when its body sizes were the smallest, whereas D. dentex showed the highest relative performance as its largest body sizes. These results will be linked to future research on both of these species concerning their escape, exploratory and predatory behaviours, and for restocking purposes to draw a more realistic overview of hatchery-reared juvenile performance. Knowledge of both species' behavioural and swimming performance through ontogeny is important to consider when using hatchery-reared fish juveniles for restocking, as size-at-release can have a large impact on fish survival and thus on restocking success. This article is protected by copyright. All rights reserved.}, } @article {pmid35750772, year = {2022}, author = {Zhang, S and Ahmad, F and Khan, A and Ali, N and Badran, M}, title = {Performance improvement and thermodynamic assessment of microchannel heat sink with different types of ribs and cones.}, journal = {Scientific reports}, volume = {12}, number = {1}, pages = {10802}, pmid = {35750772}, issn = {2045-2322}, abstract = {The present study aims to investigate the performance of microchannel heat sink via numerical simulations, based on the first and second law of thermodynamics. The heat transfer and flow characteristics of rectangular microchannel heat sinks have been improved by adding six different types of surface enhancers. The cross-sections include rectangular, triangular, and hexagonal-shaped ribs and cones. The cones have been created from the same cross-sections of ribs by drafting them at an angle of 45° orthogonal to the base, which is expected to decrease the pressure drop, dramatically. The performance of ribs and cones has been evaluated using different parameters such as friction factor, wall shear stress, entropy generation rate, augmentation entropy generation number, thermal resistance, and transport efficiency of thermal energy. The results of the present study revealed that the novel effect of coning at an angle of 45° reduces frictional losses (Maximum pressure drop reduced is 85%), however; a compromise on thermal behavior has been shown (Maximum Nusselt number reduced is 25%). Similarly, the application of coning has caused a significant reduction in wall shear stress and friction factor which can lead to reducing the pumping power requirements. Moreover, triangular ribs have more ability to transfer thermal energy than rectangular and hexagonal ribs. Furthermore, it has been examined in the present study that the trend of total entropy generation rate for triangular ribs decreases up to Re = 400 and then increases onwards which means that thermal losses are more significant than frictional losses at lower Reynolds number. However, frictional losses dominate over thermal losses at higher Reynolds numbers, where vortex generation takes place, especially in triangular ribs.}, } @article {pmid35749192, year = {2022}, author = {Buaria, D and Sreenivasan, KR}, title = {Scaling of Acceleration Statistics in High Reynolds Number Turbulence.}, journal = {Physical review letters}, volume = {128}, number = {23}, pages = {234502}, doi = {10.1103/PhysRevLett.128.234502}, pmid = {35749192}, issn = {1079-7114}, abstract = {The scaling of acceleration statistics in turbulence is examined by combining data from the literature with new data from well-resolved direct numerical simulations of isotropic turbulence, significantly extending the Reynolds number range. The acceleration variance at higher Reynolds numbers departs from previous predictions based on multifractal models, which characterize Lagrangian intermittency as an extension of Eulerian intermittency. The disagreement is even more prominent for higher-order moments of the acceleration. Instead, starting from a known exact relation, we relate the scaling of acceleration variance to that of Eulerian fourth-order velocity gradient and velocity increment statistics. This prediction is in excellent agreement with the variance data. Our Letter highlights the need for models that consider Lagrangian intermittency independent of the Eulerian counterpart.}, } @article {pmid35745944, year = {2022}, author = {Chen, D and Lin, J}, title = {Steady State of Motion of Two Particles in Poiseuille Flow of Power-Law Fluid.}, journal = {Polymers}, volume = {14}, number = {12}, pages = {}, doi = {10.3390/polym14122368}, pmid = {35745944}, issn = {2073-4360}, support = {12132015//National Natural Science Foundation of China/ ; }, abstract = {The steady state of motion of two particles in Poiseuille flow of power-law fluid is numerically studied using the lattice Boltzmann method in the range of Reynolds number 20 ≤ Re ≤ 60, diameter ratio of two particles 0.125 ≤ β ≤ 2.4, and power-law index of the fluid 0.4 ≤ n ≤ 1.2. Some results are validated by comparing with other available results. The effects of Re, β, and n on the steady state of motion of two particles are discussed. The results show that, for two particles of the same diameter, the particle spacing l in the steady state is independent of n. In shear-thinning fluid, l increases rapidly at first and then slowly, finally approaching a constant for different Re. In shear-thickening fluid, although l tends to be stable in the end, the values of l after stabilization are different. For two particles of different sizes, l does not always reach a stable state, and whether it reaches a stable state depends on n. When the small particle is downstream, l increases rapidly at first and then slowly in shear-thickening fluid, but increases rapidly at first and then decreases slowly, finally approaching a constant in a shear-thinning fluid. In shear-thinning fluid, the larger n is, the smaller l is. In shear-thickening fluid, β has no effect on l in steady-state. When the large particle is downstream, l increases rapidly at first and then slowly in shear-thinning fluid but increases rapidly at first and then decreases in a shear-thickening fluid. The effect of n on l in the steady state is obvious. In shear-thinning fluid, l increases rapidly at first and then slowly, the larger Re is, the smaller l is. In shear- thickening fluid, l will reach a stable state.}, } @article {pmid35745906, year = {2022}, author = {Bui, CM and Ho, AT and Nguyen, XB}, title = {Flow Behaviors of Polymer Solution in a Lid-Driven Cavity.}, journal = {Polymers}, volume = {14}, number = {12}, pages = {}, doi = {10.3390/polym14122330}, pmid = {35745906}, issn = {2073-4360}, support = {T2021-06-03//University of Technology and Education - The University of Danang/ ; }, abstract = {In this work, a numerical study of polymer flow behaviors in a lid-driven cavity, which is inspired by the coating process, at a broad range of Oldroyd numbers (0≤Od≤50), is carried out. The Reynolds number is height-based and kept at Re=0.001. The fluid investigated is of Carbopol gel possessing yield stress and shear-thinning properties. To express rheological characteristics, the Herschel-Bulkley model cooperated with Papanastasiou's regularization scheme is utilized. Results show that the polymer flow characteristics, i.e., velocity, viscosity, and vortex distributions, are considerably influenced by viscoplastic behaviors. Additionally, there exist solid-like regions which can be of either moving rigid or static dead types in the flow patterns; they become greater and tend to merge together to construct larger ones when Od increases. Furthermore, various polymer flow aspects in different cavity configurations are discussed and analyzed; the cavity width/aspect ratio and skewed angle are found to have significant impacts on the vortex structures and the formation of solid-like regions. Moreover, results for the critical aspect ratio at which the static dead zone is broken into two parts and the characteristic height of this zone are also reported in detail.}, } @article {pmid35744569, year = {2022}, author = {Saghir, MZ and Rahman, MM}, title = {Thermo-Hydraulic Performance of Pin-Fins in Wavy and Straight Configurations.}, journal = {Micromachines}, volume = {13}, number = {6}, pages = {}, doi = {10.3390/mi13060954}, pmid = {35744569}, issn = {2072-666X}, abstract = {Pin-fins configurations have been investigated recently for different engineering applications and, in particular, for a cooling turbine. In the present study, we investigated the performance of three different pin-fins configurations: pin-fins forming a wavy mini-channel, pin-fins forming a straight mini-channel, and a mini-channel without pin-fins considering water as the working fluid. The full Navier-Stokes equations and the energy equation are solved numerically using the finite element technique. Different flow rates are studied, represented by the Reynolds number in the laminar flow regime. The thermo-hydraulic performance of the three configurations is determined by examining the Nusselt number, the pressure drop, and the performance evaluation criterion. Results revealed that pin-fins forming a wavy mini-channel exhibited the highest Nusselt number, the lowest pressure drop, and the highest performance evaluation criterion. This finding is valid for any Reynolds number under investigation.}, } @article {pmid35744548, year = {2022}, author = {Tayeb, NT and Hossain, S and Khan, AH and Mostefa, T and Kim, KY}, title = {Evaluation of Hydrodynamic and Thermal Behaviour of Non-Newtonian-Nanofluid Mixing in a Chaotic Micromixer.}, journal = {Micromachines}, volume = {13}, number = {6}, pages = {}, doi = {10.3390/mi13060933}, pmid = {35744548}, issn = {2072-666X}, abstract = {Three-dimensional numerical investigations of a novel passive micromixer were carried out to analyze the hydrodynamic and thermal behaviors of Nano-Non-Newtonian fluids. Mass and heat transfer characteristics of two heated fluids have been investigated to understand the quantitative and qualitative fluid faction distributions with temperature homogenization. The effect of fluid behavior and different Al2O3 nanoparticles concentrations on the pressure drop and thermal mixing performances were studied for different Reynolds number (from 0.1 to 25). The performance improvement simulation was conducted in intervals of various Nanoparticles concentrations (φ = 0 to 5%) with Power-law index (n) using CFD. The proposed micromixer displayed a mixing energy cost of 50-60 comparable to that achieved for a recent micromixer (2021y) in terms of fluid homogenization. The analysis exhibited that for high nanofluid concentrations, having a strong chaotic flow enhances significantly the hydrodynamic and thermal performances for all Reynolds numbers. The visualization of vortex core region of mass fraction and path lines presents that the proposed design exhibits a rapid thermal mixing rate that tends to 0.99%, and a mass fraction mixing rate of more than 0.93% with very low pressure losses, thus the proposed micromixer can be utilized to enhance homogenization in different Nano-Non-Newtonian mechanism with minimum energy.}, } @article {pmid35739213, year = {2022}, author = {Abd-Alla, AM and Abo-Dahab, SM and Thabet, EN and Abdelhafez, MA}, title = {Peristaltic pump with heat and mass transfer of a fractional second grade fluid through porous medium inside a tube.}, journal = {Scientific reports}, volume = {12}, number = {1}, pages = {10608}, pmid = {35739213}, issn = {2045-2322}, abstract = {In magnetic resonance imaging (MRI), this MRI is used for the diagnosis of the brain. The dynamic of these particles occurs under the action of the peristaltic waves generated on the flexible walls of the brain. Studying such fluid flow of a Fractional Second-Grade under this action is therefore useful in treating tissues of cancer. This paper deals with a theoretical investigation of the interaction of heat and mass transfer in the peristaltic flow of a magnetic field fractional second-grade fluid through a tube, under the assumption of low Reynolds number and long-wavelength. The analytical solution to a problem is obtained by using Caputo's definition. The effect of different physical parameters, the material constant, magnetic field, and fractional parameter on the temperature, concentration, axial velocity, pressure gradient, pressure rise, friction forces, and coefficient of heat and mass transfer are discussed with particular emphasis. The computed results are presented in graphical form. It is because the nature of heat and mass transfer coefficient is oscillatory which is following the physical expectation due to the oscillatory nature of the tube wall. It is perceived that with an increase in Hartmann number, the velocity decreases. A suitable comparison has been made with the prior results in the literature as a limiting case of the considered problem.}, } @article {pmid35736684, year = {2022}, author = {Zubairova, US and Kravtsova, AY and Romashchenko, AV and Pushkareva, AA and Doroshkov, AV}, title = {Particle-Based Imaging Tools Revealing Water Flows in Maize Nodal Vascular Plexus.}, journal = {Plants (Basel, Switzerland)}, volume = {11}, number = {12}, pages = {}, doi = {10.3390/plants11121533}, pmid = {35736684}, issn = {2223-7747}, support = {19-74-10037//Russian Science Foundation/ ; 19-79-10217//Russian Science Foundation/ ; }, abstract = {In plants, water flows are the major driving force behind growth and play a crucial role in the life cycle. To study hydrodynamics, methods based on tracking small particles inside water flows attend a special place. Thanks to these tools, it is possible to obtain information about the dynamics of the spatial distribution of the flux characteristics. In this paper, using contrast-enhanced magnetic resonance imaging (MRI), we show that gadolinium chelate, used as an MRI contrast agent, marks the structural characteristics of the xylem bundles of maize stem nodes and internodes. Supplementing MRI data, the high-precision visualization of xylem vessels by laser scanning microscopy was used to reveal the structural and dimensional characteristics of the stem vascular system. In addition, we propose the concept of using prototype "Y-type xylem vascular connection" as a model of the elementary connection of vessels within the vascular system. A Reynolds number could match the microchannel model with the real xylem vessels.}, } @article {pmid35699409, year = {2022}, author = {Martin, AR and Finlay, WH}, title = {Empirical Deposition Correlations.}, journal = {Journal of aerosol medicine and pulmonary drug delivery}, volume = {35}, number = {3}, pages = {109-120}, doi = {10.1089/jamp.2022.29062.arm}, pmid = {35699409}, issn = {1941-2703}, mesh = {Administration, Inhalation ; Aerosols ; *Lung/diagnostic imaging ; Particle Size ; *Pharynx ; }, abstract = {Traditionally, empirical correlations for predicting respiratory tract deposition of inhaled aerosols have been developed using limited available in vivo data. More recently, advances in medical image segmentation and additive manufacturing processes have allowed researchers to conduct extensive in vitro deposition experiments in realistic replicas of the upper and central branching airways. This work has led to a collection of empirical equations for predicting regional aerosol deposition, especially in the upper, nasal and oral airways. The present section reviews empirical correlations based on both in vivo and in vitro data, which may be used to predict total and regional deposition. Equations are presented for predicting total respiratory deposition fraction, mouth-throat fraction, nasal, and nose-throat fractions for a large variety of aerosol sizes, subject age groups, and breathing maneuvers. Use of these correlations to estimate total lung deposition is also described.}, } @article {pmid35683052, year = {2022}, author = {George, GR and Bockelmann, M and Schmalhorst, L and Beton, D and Gerstle, A and Lindermeir, A and Wehinger, GD}, title = {Influence of Foam Morphology on Flow and Heat Transport in a Random Packed Bed with Metallic Foam Pellets-An Investigation Using CFD.}, journal = {Materials (Basel, Switzerland)}, volume = {15}, number = {11}, pages = {}, doi = {10.3390/ma15113754}, pmid = {35683052}, issn = {1996-1944}, support = {ZF 4640501VS8//Federal Ministry for Economic Affairs and Energy/ ; }, abstract = {Open-cell metallic foams used as catalyst supports exhibit excellent transport properties. In this work, a unique application of metallic foam, as pelletized catalyst in a packed bed reactor, is examined. By using a wall-segment Computational Fluid Dynamics (CFD) setup, parametric analyses are carried out to investigate the influence of foam morphologies (cell size ϕ=0.45-3 mm and porosity ε=0.55-0.95) and intrinsic conductivity on flow and heat transport characteristics in a slender packed bed (N=D/dp=6.78) made of cylindrical metallic foam pellets. The transport processes have been modeled using an extended version of conventional particle-resolved CFD, i.e., flow and energy in inter-particle spaces are fully resolved, whereas the porous-media model is used for the effective transport processes inside highly-porous foam pellets. Simulation inputs include the processing parameters relevant to Steam Methane Reforming (SMR), analyzed for low (Rep~100) and high (Rep~5000) flow regimes. The effect of foam morphologies on packed beds has shown that the desired requirements contradict each other, i.e., an increase in cell size and porosity favors the reduction in pressure drop, but, it reduces the heat transfer efficiency. A design study is also conducted to find the optimum foam morphology of a cylindrical foam pellet at a higher Rep~5000, which yields ϕ = 0.45, ε = 0.8. Suitable correlations to predict the friction factor and the overall heat transfer coefficient in a foam-packed bed have been presented, which consider the effect of different foam morphologies over a range of particle Reynolds number, 100≤Rep≤5000.}, } @article {pmid35676272, year = {2022}, author = {Castro, JM and Feisel, Y}, title = {Eruption of ultralow-viscosity basanite magma at Cumbre Vieja, La Palma, Canary Islands.}, journal = {Nature communications}, volume = {13}, number = {1}, pages = {3174}, pmid = {35676272}, issn = {2041-1723}, abstract = {The viscosity of magma exerts control on all aspects of its migration through the crust to eruption. This was particularly true for the 2021 eruption of Cumbre Vieja (La Palma), which produced exceptionally fast and fluid lava at high discharge rates. We have performed concentric cylinder experiments to determine the effective viscosities of the Cumbre Vieja magma, while accounting for its chemistry, crystallinity, and temperature. Here we show that this event produced a nepheline-normative basanite with the lowest viscosity of historical basaltic eruptions, exhibiting values of less than 10 to about 160 Pa s within eruption temperatures of ~1200 to ~1150 °C. The magma's low viscosity was responsible for many eruptive phenomena that lead to particularly impactful events, including high-Reynolds number turbulent flow and supercritical states. Increases in viscosity due to crystallization-induced melt differentiation were subdued in this eruption, due in part to subtle degrees of silica enrichment in alkaline magma.}, } @article {pmid35662323, year = {2022}, author = {Ruszczyk, M and Webster, DR and Yen, J}, title = {Trends in Stroke Kinematics, Reynolds Number, and Swimming Mode in Shrimp-Like Organisms.}, journal = {Integrative and comparative biology}, volume = {}, number = {}, pages = {}, doi = {10.1093/icb/icac067}, pmid = {35662323}, issn = {1557-7023}, abstract = {Metachronal propulsion is commonly seen in organisms with the caridoid facies body plan, i.e. shrimp-like organisms, as they beat their pleopods in an adlocomotory sequence. These organisms exist across length scales ranging several orders of Reynolds number magnitude, from 10 to 104, during locomotion. Further, by altering their stroke kinematics, these organisms achieve three distinct swimming modes. To better understand the relationship between Reynolds number, stroke kinematics, and resulting swimming mode, Euphausia pacifica stroke kinematics were quantified using high-speed digital recordings and compared to the results for the larger E. superba. Euphausia pacifica consistently operate with a greater beat frequency and smaller stroke amplitude than E. superba for each swimming mode, suggesting that length scale may affect the kinematics needed to achieve similar swimming modes. To expand on this observation, these euphausiid data are used in combination with previously-published stroke kinematics from mysids and stomatopods to identify broad trends across swimming mode and length scale in metachrony. Principal component analysis (PCA) reveals trends in stroke kinematics and Reynolds number as well as the variation among taxonomic order. Overall, larger beat frequencies, stroke amplitudes, between-cycle phase lags, and Reynolds numbers are more representative of the fast forward swimming mode compared to the slower hovering mode. Additionally, each species has a unique combination of kinematics that result in metachrony, indicating that there are other factors, perhaps morphological, which affect the overall metachronal characteristics of an organism. Finally, uniform phase lag, in which the timing between power strokes of all pleopods is equal, in 5-paddle systems is achieved at different Reynolds numbers for different swimming modes, highlighting the importance of taking into consideration stroke kinematics, length scale, and the resulting swimming mode.}, } @article {pmid35642428, year = {2022}, author = {Broadley, P and Nabawy, MRA and Quinn, MK and Crowther, WJ}, title = {Dynamic experimental rigs for investigation of insect wing aerodynamics.}, journal = {Journal of the Royal Society, Interface}, volume = {19}, number = {191}, pages = {20210909}, doi = {10.1098/rsif.2021.0909}, pmid = {35642428}, issn = {1742-5662}, mesh = {Animals ; Biomechanical Phenomena ; *Flight, Animal ; Insecta ; *Models, Biological ; Wings, Animal ; }, abstract = {This paper provides a systematic and critical review of dynamic experimental rigs used for insect wing aerodynamics research. The goal is to facilitate meaningful comparison of data from existing rigs and provide insights for designers of new rigs. The scope extends from simple one degree of freedom rotary rigs to multi degrees of freedom rigs allowing various rotation and translation motions. Experimental methods are characterized using a consistent set of parameters that allows objective comparison of different approaches. A comprehensive catalogue is presented for the tested flow conditions (assessed through Reynolds number, Rossby number and advance ratio), wing morphologies (assessed through aspect ratio, planform shape and thickness to mean chord ratio) and kinematics (assessed through motion degrees of freedom). Links are made between the type of aerodynamic characteristics being studied and the type of experimental set-up used. Rig mechanical design considerations are assessed, and the aerodynamic measurements obtained from these rigs are discussed.}, } @article {pmid35637889, year = {2022}, author = {Semenov, AP and Mendgaziev, RI and Stoporev, AS and Istomin, VA and Sergeeva, DV and Tulegenov, TB and Vinokurov, VA}, title = {Dataset for the dimethyl sulfoxide as a novel thermodynamic inhibitor of carbon dioxide hydrate formation.}, journal = {Data in brief}, volume = {42}, number = {}, pages = {108289}, doi = {10.1016/j.dib.2022.108289}, pmid = {35637889}, issn = {2352-3409}, abstract = {The temperatures and pressures of the three-phase equilibrium V-Lw-H (gas - aqueous solution - gas hydrate) were measured in the CO2 - H2O - dimethyl sulfoxide (DMSO) system at concentrations of organic solute in the aqueous phase up to 50 mass%. Measurements of CO2 hydrate equilibrium conditions were carried out using a constant volume autoclave by continuous heating at a rate of 0.1 K/h with simultaneous stirring of fluids by a four-blade agitator at 600 rpm. The equilibrium temperature and pressure of CO2 hydrate were determined for the endpoint of the hydrate dissociation in each experiment. The CO2 gas fugacity was calculated by the equation of state for carbon dioxide for the measured points. The flow regime in the autoclave during the operation of the stirring system was characterized by calculating the Reynolds number using literature data on the viscosity and density of water and DMSO aqueous solutions. We employed regression analysis to approximate the dependences of equilibrium pressure (CO2 gas fugacity) on temperature by two- and three-parameter equations. For each measured point, the value of CO2 hydrate equilibrium temperature suppression ΔTh was computed. The dependences of this quantity on CO2 gas fugacity are considered for all DMSO concentrations. The coefficients of empirical correlation describing ΔTh as a function of the DMSO mass fraction in solution and the equilibrium gas pressure are determined. This article is a co-submission with a paper [1].}, } @article {pmid35635664, year = {2022}, author = {Eldesoukey, A and Hassan, H}, title = {Study of the performance of thermoelectric generator for waste heat recovery from chimney: impact of nanofluid-microchannel cooling system.}, journal = {Environmental science and pollution research international}, volume = {}, number = {}, pages = {}, pmid = {35635664}, issn = {1614-7499}, abstract = {A huge number of chimneys all over the world utilized in many industrial applications and applications like restaurants, homes, etc. contribute badly on the global warming and climate change due to their waste heat. So, in this paper, the performance of thermoelectric generator (TEG) cooled by microchannel heat spreader having nanofluid and used for waste heat recovery from vertical chimney is investigated. Using heat spreader with microchannel cooling system increases the output TEG power compared to natural convection cooling system. In this paper, the impact of microchannel sizes, using nanofluid and heat spreader with different sizes on the TEG performance and cooling, is considered. Three-dimensional mathematical models including TEG, microchannel, nanofluid, and heat spreader are presented and solved by Ansys Fluent software utilizing user-defined memory, user-defined function, and user-defined scalar. All TEG effects (Joule, Seebeck, and Thomson) are considered in TEG model. Results indicate that TEG power rises with increasing the heat spreader and microchannel sizes together. Increasing microchannel and heat spreader sizes four times of TEG size raises the TEG output power by 10%. This also achieves the maximum cooling system efficiency of 88.9% and the maximum net output power. Microchannel heat spreader cooling system raises the system (TEG power-pumping power) net power by 125.2% compared to the normal channel and decreases the required cooling fluid flow rate. Utilizing copper-water and Al2O3-water nanofluids rises maximally the TEG output power by 14% and 4%, respectively; however, it increases the pumping power. Moreover, using nanofluids increases the net output power at low Reynolds number and decreases it at higher Reynolds number.}, } @article {pmid35630837, year = {2022}, author = {Souayeh, B and Ramesh, K and Hdhiri, N and Yasin, E and Alam, MW and Alfares, K and Yasin, A}, title = {Heat Transfer Attributes of Gold-Silver-Blood Hybrid Nanomaterial Flow in an EMHD Peristaltic Channel with Activation Energy.}, journal = {Nanomaterials (Basel, Switzerland)}, volume = {12}, number = {10}, pages = {}, doi = {10.3390/nano12101615}, pmid = {35630837}, issn = {2079-4991}, support = {AN00052//Deanship of Scientific Research at King Faisal University/ ; }, abstract = {The heat enhancement in hybrid nanofluid flow through the peristaltic mechanism has received great attention due to its occurrence in many engineering and biomedical systems, such as flow through canals, the cavity flow model and biomedicine. Therefore, the aim of the current study was to discuss the hybrid nanofluid flow in a symmetric peristaltic channel with diverse effects, such as electromagnetohydrodynamics (EMHD), activation energy, gyrotactic microorganisms and solar radiation. The equations governing this motion were simplified under the approximations of a low Reynolds number (LRN), a long wavelength (LWL) and Debye-Hückel linearization (DHL). The numerical solutions for the non-dimensional system of equations were tackled using the computational software Mathematica. The influences of diverse physical parameters on the flow and thermal characteristics were computed through pictorial interpretations. It was concluded from the results that the thermophoresis parameter and Grashof number increased the hybrid nanofluid velocity near the right wall. The nanoparticle temperature decreased with the radiation parameter and Schmidt number. The activation energy and radiation enhanced the nanoparticle volume fraction, and motile microorganisms decreased with an increase in the Peclet number and Schmidt number. The applications of the current investigation include chyme flow in the gastrointestinal tract, the control of blood flow during surgery by altering the magnetic field and novel drug delivery systems in pharmacological engineering.}, } @article {pmid35630375, year = {2022}, author = {Soares, A and Gomes, LC and Monteiro, GA and Mergulhão, FJ}, title = {Hydrodynamic Effects on Biofilm Development and Recombinant Protein Expression.}, journal = {Microorganisms}, volume = {10}, number = {5}, pages = {}, doi = {10.3390/microorganisms10050931}, pmid = {35630375}, issn = {2076-2607}, support = {LA/P/0045/2020 (ALiCE), UIDB/00511/2020 and UIDP/00511/2020 (LEPABE)//FCT/MCTES (PIDDAC)/ ; PTDC/BII-BIO/29589/2017 - POCI-01-0145-FEDER-029589//FEDER funds through COMPETE2020 - Programa Operacional Competitividade e Internacionalização (POCI) and by national funds (PIDDAC) through FCT/MCTES/ ; SFRH/BD/141614/2018; CEECIND/01700/2017//FCT/ ; }, abstract = {Hydrodynamics play an important role in the rate of cell attachment and nutrient and oxygen transfer, which can affect biofilm development and the level of recombinant protein production. In the present study, the effects of different flow conditions on the development of Escherichia coli biofilms and the expression of a model recombinant protein (enhanced green fluorescent protein, eGFP) were examined. Planktonic and biofilm cells were grown at two different flow rates in a recirculating flow cell system for 7 days: 255 and 128 L h-1 (corresponding to a Reynolds number of 4600 and 2300, respectively). The fluorometric analysis showed that the specific eGFP production was higher in biofilms than in planktonic cells under both hydrodynamic conditions (3-fold higher for 255 L h-1 and 2-fold higher for 128 L h-1). In the biofilm cells, the percentage of eGFP-expressing cells was on average 52% higher at a flow rate of 255 L h-1. Furthermore, a higher plasmid copy number (PCN) was obtained for the highest flow rate for both planktonic (244 PCN/cell versus 118 PCN/cell) and biofilm cells (43 PCN/cell versus 29 PCN/cell). The results suggested that higher flow velocities promoted eGFP expression in E. coli biofilms.}, } @article {pmid35626546, year = {2022}, author = {Alenezi, A and Almutairi, A and Alhajeri, H and Almekmesh, SF and Alzuwayer, BB}, title = {Impact of Surface Roughness on Flow Physics and Entropy Generation in Jet Impingement Applications.}, journal = {Entropy (Basel, Switzerland)}, volume = {24}, number = {5}, pages = {}, doi = {10.3390/e24050661}, pmid = {35626546}, issn = {1099-4300}, abstract = {In this paper, a numerical investigation was performed of an air jet incident that normally occurs on a horizontal heated plane. Analysis of flow physics and entropy generation due to heat and friction is included using a simple easy-to-manufacture, surface roughening element: a circular rib concentric with the air jet. This study shows how varying the locations and dimensions of the rib can deliver a favorable trade-off between entropy generation and flow parameters, such as vortex generation and heat transfer. The performance of the roughness element was tested at three different radii; R/D = 1, 1.5 and 2, where D was the jet hydraulic diameter and R was the radial distance from the geometric center. At each location, the normalized rib height (e/D) was increased from 0.019 to 0.074 based on an increment of (e/D) = 0.019. The jet-to-target distance was H/D = 6 and the jet Reynolds number (Re) ranged from 10,000 to 50,000 Re, which was obtained from the jet hydraulic diameter (D), and the jet exit velocity (U). All results are presented in the form of entropy generation due to friction and heat exchange, as well as the total entropy generated. A detailed comparison of flow physics is presented for all ribs and compared with the baseline case of a smooth surface. The results show that at higher Reynolds numbers, adding a rib of a suitable height reduced the total entropy (St) by 31% compared to the no rib case. In addition, with ribs of heights 0.019, 0.037 and 0.054, respectively, the entropy generated by friction (Sf) was greater than that due to heat exchange (Sh) by about 42%, 26% and 4%, respectively. The rib of height e/D = 0.074 produced the minimum St at R/D = 1. As for varying R/D, varying rib location and Re values had a noticeable impact on Sh, Sf and (St). Placing the rib at R/D = 1 gave the highest total entropy generation (St) followed by R/D = 1.5 for all Re. Finally, the Bejan number increased as both rib height and rib location increased.}, } @article {pmid35626500, year = {2022}, author = {Dressler, L and Nicolai, H and Agrebi, S and Ries, F and Sadiki, A}, title = {Computation of Entropy Production in Stratified Flames Based on Chemistry Tabulation and an Eulerian Transported Probability Density Function Approach.}, journal = {Entropy (Basel, Switzerland)}, volume = {24}, number = {5}, pages = {}, doi = {10.3390/e24050615}, pmid = {35626500}, issn = {1099-4300}, support = {SA 836/15-1//Deutsche Forschungsgemeinschaft/ ; }, abstract = {This contribution presents a straightforward strategy to investigate the entropy production in stratified premixed flames. The modeling approach is grounded on a chemistry tabulation strategy, large eddy simulation, and the Eulerian stochastic field method. This enables a combination of a detailed representation of the chemistry with an advanced model for the turbulence chemistry interaction, which is crucial to compute the various sources of exergy losses in combustion systems. First, using detailed reaction kinetic reference simulations in a simplified laminar stratified premixed flame, it is demonstrated that the tabulated chemistry is a suitable approach to compute the various sources of irreversibilities. Thereafter, the effects of the operating conditions on the entropy production are investigated. For this purpose, two operating conditions of the Darmstadt stratified burner with varying levels of shear have been considered. The investigations reveal that the contribution to the entropy production through mixing emerging from the chemical reaction is much larger than the one caused by the stratification. Moreover, it is shown that a stronger shear, realized through a larger Reynolds number, yields higher entropy production through heat, mixing and viscous dissipation and reduces the share by chemical reaction to the total entropy generated.}, } @article {pmid35621794, year = {2022}, author = {Li, H and Nabawy, MRA}, title = {Wing Planform Effect on the Aerodynamics of Insect Wings.}, journal = {Insects}, volume = {13}, number = {5}, pages = {}, doi = {10.3390/insects13050459}, pmid = {35621794}, issn = {2075-4450}, support = {RPG-2019-366//Leverhulme Trust/ ; }, abstract = {This study investigates the effect of wing planform shape on the aerodynamic performance of insect wings by numerically solving the incompressible Navier-Stokes equations. We define the wing planforms using a beta-function distribution and employ kinematics representative of normal hovering flight. In particular, we use three primary parameters to describe the planform geometry: aspect ratio, radial centroid location, and wing root offset. The force coefficients, flow structures, and aerodynamic efficiency for different wing planforms at a Reynolds number of 100 are evaluated. It is found that the wing with the lowest aspect ratio of 1.5 results in the highest peaks of lift and drag coefficients during stroke reversals, whereas the higher aspect ratio wings produce higher lift and drag coefficients during mid half-stroke translation. For the wings considered, the leading-edge vortex detachment is found to be approximately at a location that is 3.5-5 mean chord lengths from the wing center of rotation for all aspect ratios and root offsets investigated. Consequently, the detachment area increases with the increase of aspect ratio and root offset, resulting in reduced aerodynamic coefficients. The radial centroid location is found to influence the local flow evolution time, and this results in earlier formation/detachment of the leading-edge vortex for wings with a smaller radial centroid location. Overall, the best performance, when considering both average lift coefficient and efficiency, is found at the intermediate aspect ratios of 4.5-6; increasing the centroid location mainly increases efficiency; and increasing the root offset leads to a decreased average lift coefficient whilst leading to relatively small variations in aerodynamic efficiency for most aspect ratios.}, } @article {pmid35617810, year = {2022}, author = {Huang, F and Noël, R and Berg, P and Hosseini, SA}, title = {Simulation of the FDA nozzle benchmark: A lattice Boltzmann study.}, journal = {Computer methods and programs in biomedicine}, volume = {221}, number = {}, pages = {106863}, doi = {10.1016/j.cmpb.2022.106863}, pmid = {35617810}, issn = {1872-7565}, abstract = {BACKGROUND AND OBJECTIVE: Contrary to flows in small intracranial vessels, many blood flow configurations such as those found in aortic vessels and aneurysms involve larger Reynolds numbers and, therefore, transitional or turbulent conditions. Dealing with such systems require both robust and efficient numerical methods.

METHODS: We assess here the performance of a lattice Boltzmann solver with full Hermite expansion of the equilibrium and central Hermite moments collision operator at higher Reynolds numbers, especially for under-resolved simulations. To that end the food and drug administration's benchmark nozzle is considered at three different Reynolds numbers covering all regimes: (1) laminar at a Reynolds number of 500, (2) transitional at a Reynolds number of 3500, and (3) low-level turbulence at a Reynolds number of 6500.

RESULTS: The lattice Boltzmann results are compared with previously published inter-laboratory experimental data obtained by particle image velocimetry. Our results show good agreement with the experimental measurements throughout the nozzle, demonstrating the good performance of the solver even in under-resolved simulations.

CONCLUSION: In this manner, fast but sufficiently accurate numerical predictions can be achieved for flow configurations of practical interest regarding medical applications.}, } @article {pmid35598483, year = {2022}, author = {Sharma, S and Jain, S and Saha, A and Basu, S}, title = {Evaporation dynamics of a surrogate respiratory droplet in a vortical environment.}, journal = {Journal of colloid and interface science}, volume = {623}, number = {}, pages = {541-551}, doi = {10.1016/j.jcis.2022.05.061}, pmid = {35598483}, issn = {1095-7103}, abstract = {HYPOTHESIS: Vortex droplet interaction is crucial for understanding the route of disease transmission through expiratory jet where several such embedded droplets continuously interact with vortical structures of different strengths and sizes.

EXPERIMENTS: A train of vortex rings with different vortex strength, quantified with vortex Reynolds number (Re'=0,53,221,297) are made to interact with an isolated levitated droplet, and the evolution dynamics is captured using shadowgraphy, particle image velocimetry (PIV), and backlight imaging technique. NaCl-DI water solution of 0, 1, 10 and 20 wt% concentrations are used as test fluids for the droplet.

FINDINGS: The results show the dependence of evaporation characteristics on vortex strength, while the crystallization dynamics was found to be independent of it. A reduction of 12.23% and 14.6% in evaporation time was seen in case of de-ionized (DI) water and 1% wt NaCl solution respectively in presence of vortex ring train at Re'=221. In contrast to this, a minimal reduction in evaporation time (0.6% and 0.9% for DI water and 1% wt NaCl solution, respectively) is observed when Re' is increased from 221 to 297. The mechanisms for evaporation time reduction due to enhancement of convective heat and mass transfer from the droplet and shearing away of vapor layer by vortex ring interaction are discussed in this work.}, } @article {pmid35591423, year = {2022}, author = {Karmveer, and Kumar Gupta, N and Siddiqui, MIH and Dobrotă, D and Alam, T and Ali, MA and Orfi, J}, title = {The Effect of Roughness in Absorbing Materials on Solar Air Heater Performance.}, journal = {Materials (Basel, Switzerland)}, volume = {15}, number = {9}, pages = {}, doi = {10.3390/ma15093088}, pmid = {35591423}, issn = {1996-1944}, abstract = {Artificial roughness on the absorber of the solar air heater (SAH) is considered to be the best passive technology for performance improvement. The roughened SAHs perform better in comparison to conventional SAHs under the same operational conditions, with some penalty of higher pumping power requirements. Thermo-hydraulic performance, based on effective efficiency, is much more appropriate to design roughened SAH, as it considers both the requirement of pumping power and useful heat gain. The shape, size, and arrangement of artificial roughness are the most important factors for the performance optimization of SAHs. The parameters of artificial roughness and operating parameters, such as the Reynolds number (Re), temperature rise parameter (ΔT/I) and insolation (I) show a combined effect on the performance of SAH. In this case study, various performance parameters of SAH have been evaluated to show the effect of distinct artificial roughness, investigated previously. Therefore, thermal efficiency, thermal efficiency improvement factor (TEIF) and the effective efficiency of various roughened absorbers of SAH have been predicted. As a result, thermal and effective efficiencies strongly depend on the roughness parameter, Re and ΔT/I. Staggered, broken arc hybrid-rib roughness shows a higher value of TEIF, thermal and effective efficiencies consistently among all other distinct roughness geometries for the ascending values of ΔT/I. This roughness shows the maximum value of effective efficiency equals 74.63% at a ΔT/I = 0.01 K·m2/W. The unique combination of parameters p/e = 10, e/Dh = 0.043 and α = 60° are observed for best performance at a ΔT/I higher than 0.00789 K·m2/W.}, } @article {pmid35591154, year = {2022}, author = {Salem, S and Fraňa, K}, title = {A Wind Tunnel Study of the Flow-Induced Vibrations of a Cylindrical Piezoelectric Transducer.}, journal = {Sensors (Basel, Switzerland)}, volume = {22}, number = {9}, pages = {}, pmid = {35591154}, issn = {1424-8220}, support = {SGS-2022-5040//Technical University of Liberec - SGS/ ; CZ.02.1.01/0.0/0.0/16_019/0000843//European Union and the Czech Government/ ; }, abstract = {Piezoelectric transducers are used as a sensing device to study the fluids' motion. Moreover, they are used as a harvester of energy of Flow-Induced Vibration (FIV). The current FIV harvesters in the literature rely on piezoelectric cantilevers coupled with a bluff body that creates flow instabilities. This paper studies the use of piezoelectric cylinders as a novel transducer in the field of fluid mechanics, where the transducer makes use of its bluff geometry to create instability. The study was based on wind tunnel measurements performed on four piezoelectric cylinders of different sizes over a speed range of 1-7 m/s. The paper looks at the variation of the generated voltage across the Reynolds number. It also compares the spectra of the generated open-circuit voltage to the turbulence spectra features known from the literature.}, } @article {pmid35590864, year = {2022}, author = {Funatani, S and Tsukamoto, Y and Toriyama, K}, title = {Temperature Measurement of Hot Airflow Using Ultra-Fine Thermo-Sensitive Fluorescent Wires.}, journal = {Sensors (Basel, Switzerland)}, volume = {22}, number = {9}, pages = {}, pmid = {35590864}, issn = {1424-8220}, abstract = {In this paper, we propose a temperature measurement method that uses ultrafine fluorescent wires to reduce the wire diameter to a much lesser extent than a thermocouple. This is possible because its structure is simple and any material can be used for the wire. Hence, ultrafine wires with a Reynolds number of less than 1.0 can be selected. Ultra-fine wires less than 50 µm in diameter were set in the test volume. The wire surfaces were coated with fluorescent paint. The test volume was illuminated using an ultraviolet light-emitting diode. The paint emits very tiny, orange-colored fluorescent light with an intensity that changes with the temperature of the atmosphere. The experimental results showed that the heating/cooling layers were well visualized and the temperature field was well analyzed.}, } @article {pmid35590633, year = {2022}, author = {Wang, G and Fei, L and Luo, KH}, title = {Unified lattice Boltzmann method with improved schemes for multiphase flow simulation: Application to droplet dynamics under realistic conditions.}, journal = {Physical review. E}, volume = {105}, number = {4-2}, pages = {045314}, doi = {10.1103/PhysRevE.105.045314}, pmid = {35590633}, issn = {2470-0053}, abstract = {As a powerful mesoscale approach, the lattice Boltzmann method (LBM) has been widely used for the numerical study of complex multiphase flows. Recently, Luo et al. [Philos. Trans. R. Soc. A: Math. Phys. Eng. Sci. 379, 20200397 (2021)10.1098/rsta.2020.0397] proposed a unified lattice Boltzmann method (ULBM) to integrate the widely used lattice Boltzmann collision operators into a unified framework. In this study, we incorporate additional features into this ULBM in order to simulate multiphase flow under realistic conditions. A nonorthogonal moment set [Fei et al., Phys. Rev. E 97, 053309 (2018)10.1103/PhysRevE.97.053309] and the entropic-multi-relaxation-time (KBC) lattice Boltzmann model are used to construct the collision operator. An extended combined pseudopotential model is proposed to realize multiphase flow simulation at high-density ratio with tunable surface tension over a wide range. The numerical results indicate that the improved ULBM can significantly decrease the spurious velocities and adjust the surface tension without appreciably changing the density ratio. The ULBM is validated through reproducing various droplet dynamics experiments, such as binary droplet collision and droplet impingement on superhydrophobic surfaces. Finally, the extended ULBM is applied to complex droplet dynamics, including droplet pancake bouncing and droplet splashing. The maximum Weber number and Reynolds number in the simulation reach 800 and 7200, respectively, at a density ratio of 1000. The study demonstrates the generality and versatility of ULBM for incorporating schemes to tackle challenging multiphase problems.}, } @article {pmid35590627, year = {2022}, author = {Verma, S and Hemmati, A}, title = {Route to transition in propulsive performance of oscillating foil.}, journal = {Physical review. E}, volume = {105}, number = {4-2}, pages = {045102}, doi = {10.1103/PhysRevE.105.045102}, pmid = {35590627}, issn = {2470-0053}, abstract = {Transition in the propulsive performance and vortex synchronization of an oscillating foil in a combined heaving and pitching motion is numerically investigated at a range of reduced frequencies (0.16 ≤f^{*} ≤ 0.64), phase offsets (0^{∘} ≤ϕ≤ 315^{∘} ), and Reynolds number (1000≤Re≤16000). Focusing on the common case of Re=1000, the drag to thrust transition is identified on a ϕ-f^{*} phase map. Here, the range of 90^{∘} ≤ϕ≤ 225^{∘} depicted a drag-dominated regime for increasing reduced frequency. However, thrust-dominated regimes were observed for ϕ< 90^{∘} and ϕ> 225^{∘}, where increasing the reduced frequency led to an increased thrust production. The isoline-depicting drag-thrust boundary was further observed to coincide with transitions in the characteristic near-wake modes with increasing reduced frequency, which ranged from 2P+2S to 2P and reverse von Kármán modes. However, evaluation of the wake with changing phase offsets at individual reduced frequencies only depicted effects on the spatial configuration of the vortex structures, while the number of vortices shed in one oscillation period was unchanged. The existence of similar wake modes with significantly different propulsive performance clearly suggests that transitions of the wake topology may not always be a reliable tool for understanding propulsive mechanisms of fish swimming or development of underwater propulsion systems. We further assessed a possible route to drag production via investigation into the mean velocity fields at increasing phase offset and at intermediate reduced frequencies ranging from 0.24 to 0.40. This revealed bifurcation of a velocity jet behind the foil on account of the wake topology and dynamics of shed vortex structures. The changes posed by increasing ϕ on wake structure interactions further hints at potential mechanisms that limit the achievement of optimum efficiency in underwater locomotion.}, } @article {pmid35580542, year = {2022}, author = {Ge, M and Sun, C and Zhang, G and Coutier-Delgosha, O and Fan, D}, title = {Combined suppression effects on hydrodynamic cavitation performance in Venturi-type reactor for process intensification.}, journal = {Ultrasonics sonochemistry}, volume = {86}, number = {}, pages = {106035}, doi = {10.1016/j.ultsonch.2022.106035}, pmid = {35580542}, issn = {1873-2828}, abstract = {Hydrodynamic cavitation is an emerging intensification technology in water treatment or chemical processing, and Venturi-type cavitation reactors exhibit advantages for industrial-scale production. The effects of temperature on hydrodynamic cavitating flows are investigated to find the optimum reaction conditions enhancing cavitating treatment intensity. Results show that the cavitation performance, including the cavitation intensity and cavitation unsteady behavior, is influenced by (1) cavitation number σ (the pressure difference affecting the vaporization process), (2) Reynolds number Re (the inertial/viscous ratio affecting the bubble size and liquid-vapor interface area), and (3) thermodynamic parameter Σ (the thermal effect affecting the temperature drop). With increasing temperature, the cavitation length first increases and then decreases, with a cavitation intensity peak at the transition temperature of 58 °C. With the growth of cavitation extent, the cavity-shedding regimes tend to transition from the attached sheet cavity to the periodic cloud cavity, and the vapor volume fluctuating frequency decreases accordingly. A combined suppression parameter (CSP) is provided to predict that, with increasing CSP value, the cavitation intensity can be decreased. Recommendations are given that working under the low-CSP range (55-60 °C) could enhance the intensification of the cavitation process.}, } @article {pmid35567865, year = {2022}, author = {Cherkaoui, I and Bettaibi, S and Barkaoui, A and Kuznik, F}, title = {Magnetohydrodynamic blood flow study in stenotic coronary artery using lattice Boltzmann method.}, journal = {Computer methods and programs in biomedicine}, volume = {221}, number = {}, pages = {106850}, doi = {10.1016/j.cmpb.2022.106850}, pmid = {35567865}, issn = {1872-7565}, abstract = {BACKGROUND AND OBJECTIVE: Cardiovascular diseases such as atherosclerosis are the first engender of death in the world. The malfunctioning of cardiovascular system is attributed mainly to hemodynamics. However, blood magnetic properties are of major haemodynamic interest, with significant clinical applications. The aim of this work is to study numerically the effect of high magnetic field on blood flow in stenotic artery.

METHODS: In this paper, a double population D2Q9 lattice Boltzmann model is proposed. Velocity and magnetic field are both solved using Lattice Boltzmann method with single relaxation time. Blood is considered homogeneous and Newtonian bio-magnetic fluid. The results of the proposed model are compared and validated by recent numerical and experimental studies in the literature and show good agreement. In this study, simulations are carried out for both hydrodynamics and magneto-hydrodynamics. For the magneto-hydrodynamic case, five values of Hartmann number of 10, 30, 50, 75 and 100 at Reynolds number of 400, 600 and 800 are investigated Results: The results show that velocity and recirculation zone increase with the increase of the degree of stenosis and Reynolds number. In addition, a considerable decrease in velocity, recirculation zones and pressure drop across the stenotic artery is noticed with the increase of Hartmann number.

CONCLUSION: The suggested model is found to be effective and accurate in the treatment of magneto-hydrodynamic blood flow in stenotic artery. The found results can be used by clinicians in the treatment of certain cardiovascular disorders and in regulating blood flow movement, especially during surgical procedures.}, } @article {pmid35551230, year = {2022}, author = {Chew, SH and Hoi, SM and Tran, MV and Foo, JJ}, title = {Partially-covered fractal induced turbulence on fins thermal dissipation.}, journal = {Scientific reports}, volume = {12}, number = {1}, pages = {7861}, pmid = {35551230}, issn = {2045-2322}, support = {FRGS/1/2018/TK07/MUSM/02/1//Ministry of Higher Education, Malaysia/ ; FRGS/1/2018/TK07/MUSM/02/1//Ministry of Higher Education, Malaysia/ ; MUM25929267//Monash University Malaysia/ ; }, abstract = {The impacts of partially-covered fractal grids induced turbulence on the forced convective heat transfer across plate-fin heat sink at Reynolds number ReDh = 22.0 × 103 were numerically and experimentally investigated. Results showed that partially covered grids rendered a higher thermal dissipation performance, with partially-covered square fractal grid (PCSFG) registering an outstanding increase of 43% in Nusselt number relative to the no grid configuration. The analyzation via an in-house developed single particle tracking velocimetry (SPTV) system displayed the findings of unique "Turbulence Annulus" formation, which provided a small degree of predictivity in the periodic annulus oscillations. Further assessments on PCSFG revealed the preferred inter-fin flow dynamics of (i) high flow velocity, (ii) strong turbulence intensity, (iii) vigorous flow fluctuations, (iv) small turbulence length scale, and (v) heightened decelerated flow events. These features stemmed from the coupling effects of multilength-scale fractal bar thicknesses in generating a veracity of eddy sizes, and a vertical segmentation producing heightened mass flow rate while inducing favourable wake-flow structures to penetrate inter-fin regions. Teeming effects of such energetic eddies within plate-fin array unveiled a powerful vortex shedding effect, with PCSFG achieving fluctuation frequency f = 18.5 Hz close to an optimal magnitude. The coaction of such traits limits the growth of fin boundary layers, providing superior thermal transfer capabilities which benefits the community in developing for higher efficiency heat transfer systems.}, } @article {pmid35547578, year = {2022}, author = {Qiao, Y and Luo, K and Fan, J}, title = {Computational Prediction of Thrombosis in Food and Drug Administration's Benchmark Nozzle.}, journal = {Frontiers in physiology}, volume = {13}, number = {}, pages = {867613}, pmid = {35547578}, issn = {1664-042X}, abstract = {Thrombosis seriously threatens human cardiovascular health and the safe operation of medical devices. The Food and Drug Administration's (FDA) benchmark nozzle model was designed to include the typical structure of medical devices. However, the thrombosis in the FDA nozzle has yet not been investigated. The objective of this study is to predict the thrombus formation process in the idealized medical device by coupling computational fluid dynamics and a macroscopic hemodynamic-based thrombus model. We developed the hemodynamic-based thrombus model by considering the effect of platelet consumption. The thrombus model was quantitatively validated by referring to the latest thrombosis experiment, which was performed in a backward-facing step with human blood flow. The same setup was applied in the FDA nozzle to simulate the thrombus formation process. The thrombus shaped like a ring was firstly observed in the FDA benchmark nozzle. Subsequently, the accuracy of the shear-stress transport turbulence model was confirmed in different turbulent flow conditions. Five scenarios with different Reynolds numbers were carried out. We found that turbulence could change the shape of centrosymmetric thrombus to axisymmetric and high Reynolds number blood flow would delay or even prevent thrombosis. Overall, the present study reports the thrombosis process in the FDA benchmark nozzle using the numerical simulation method, and the primary findings may shed light on the effect of turbulence on thrombosis.}, } @article {pmid35546646, year = {2022}, author = {Gil, A and Navarro, R and Quintero, P and Mares, A and Pérez, M and Montero, JA}, title = {CFD analysis of the HVAD's hemodynamic performance and blood damage with insight into gap clearance.}, journal = {Biomechanics and modeling in mechanobiology}, volume = {}, number = {}, pages = {}, pmid = {35546646}, issn = {1617-7940}, support = {MODELVAD//Fundación para la Investigación del Hospital Universitari La Fe/ ; }, abstract = {Mechanical circulatory support using ventricular assist devices has become commonplace in the treatment of patients suffering from advanced stages of heart failure. While blood damage generated by these devices has been evaluated in depth, their hemodynamic performance has been investigated much less. This work presents the analysis of the complete operating map of a left ventricular assist device, in terms of pressure head, power and efficiency. Further investigation into its hemocompatibility is included as well. To achieve these objectives, computational fluid dynamics simulations of a centrifugal blood pump with a wide-blade impeller were performed. Several conditions were considered by varying the rotational speed and volumetric flow rate. Regarding the device's hemocompatibility, blood damage was evaluated by means of the hemolysis index. By relating the hemocompatibility of the device to its hemodynamic performance, the results have demonstrated that the highest hemolysis occurs at low flow rates, corresponding to operating conditions of low efficiency. Both performance and hemocompatibility are affected by the gap clearance. An innovative investigation into the influence of this design parameter has yielded decreased efficiencies and increased hemolysis as the gap clearance is reduced. As a further novelty, pump operating maps were non-dimensionalized to highlight the influence of Reynolds number, which allows their application to any working condition. The pump's operating range places it in the transitional regime between laminar and turbulent, leading to enhanced efficiency for the highest Reynolds number.}, } @article {pmid35544978, year = {2022}, author = {Sander, A and Petračić, A and Zokić, I and Vrsaljko, D}, title = {Scaling up extractive deacidification of waste cooking oil.}, journal = {Journal of environmental management}, volume = {316}, number = {}, pages = {115222}, doi = {10.1016/j.jenvman.2022.115222}, pmid = {35544978}, issn = {1095-8630}, mesh = {*Biofuels/analysis ; Cooking ; *Fatty Acids, Nonesterified ; Plant Oils ; Solvents ; }, abstract = {Biodiesel produced from waste feedstocks can play a significant role in fighting climate change, improperly disposed waste and growing energy demand. Waste feedstocks such as used cooking oil have a great potential for energy production. However, they often have to be purified from free fatty acids prior to biodiesel production. Extractive deacidification with deep eutectic solvents is a promising alternative to conventional purification methods. To evaluate the process of extractive deacidification of waste cooking oil, a full set of physical, hydrodynamic and kinetic data were experimentally determined on a laboratory scale. Hydrodynamic and kinetic experiments were performed in three geometrically similar jacketed agitated vessels. Vessels were equipped with axial flow impeller (four pitched blade impeller). Physical properties (density, viscosity and surface tension) were experimentally determined. Preliminary hydrodynamic experiments involved several model systems without mass transfer. As a result, correlation between power number and Reynolds number as well as scale-up criterion was developed. Obtained dependencies were correlated with the physical properties. Mixing intensity for achieving complete dispersion was determined. Second stage of investigation involved two sets of experiments, hydrodynamic and kinetic, with interphase mass transfer (the extraction of free fatty acids from waste cooking oil with deep eutectic solvent, potassium carbonate:ethylene glycol, 1:10). Obtained results enabled understanding interphase mass transfer and prediction of mass transfer coefficient from the derived dimensionless correlations. The values of volumetric mass transfer coefficients were smaller for the dispersed phase, indicating that the prevailing mass transfer resistance was within the droplets. The working hypothesis was that the same process result should be achieved at the same dispersion rate, and that hypothesis was confirmed - at all scales extraction efficiency was 97.9 ± 0.1%.}, } @article {pmid35544559, year = {2022}, author = {Callaham, JL and Rigas, G and Loiseau, JC and Brunton, SL}, title = {An empirical mean-field model of symmetry-breaking in a turbulent wake.}, journal = {Science advances}, volume = {8}, number = {19}, pages = {eabm4786}, doi = {10.1126/sciadv.abm4786}, pmid = {35544559}, issn = {2375-2548}, abstract = {Improved turbulence modeling remains a major open problem in mathematical physics. Turbulence is notoriously challenging, in part due to its multiscale nature and the fact that large-scale coherent structures cannot be disentangled from small-scale fluctuations. This closure problem is emblematic of a greater challenge in complex systems, where coarse-graining and statistical mechanics descriptions break down. This work demonstrates an alternative data-driven modeling approach to learn nonlinear models of the coherent structures, approximating turbulent fluctuations as state-dependent stochastic forcing. We demonstrate this approach on a high-Reynolds number turbulent wake experiment, showing that our model reproduces empirical power spectra and probability distributions. The model is interpretable, providing insights into the physical mechanisms underlying the symmetry-breaking behavior in the wake. This work suggests a path toward low-dimensional models of globally unstable turbulent flows from experimental measurements, with broad implications for other multiscale systems.}, } @article {pmid35535750, year = {2022}, author = {Zhang, R and Toonder, JD and Onck, PR}, title = {Metachronal patterns by magnetically-programmable artificial cilia surfaces for low Reynolds number fluid transport and mixing.}, journal = {Soft matter}, volume = {18}, number = {20}, pages = {3902-3909}, doi = {10.1039/d1sm01680f}, pmid = {35535750}, issn = {1744-6848}, mesh = {Biological Transport ; *Cilia/metabolism ; *Magnetics ; Models, Biological ; Motion ; }, abstract = {Motile cilia can produce net fluid flows at low Reynolds number because of their asymmetric motion and metachrony of collective beating. Mimicking this with artificial cilia can find application in microfluidic devices for fluid transport and mixing. Here, we study the metachronal beating of nonidentical, magnetically-programmed artificial cilia whose individual non-reciprocal motion and collective metachronal beating pattern can be independently controlled. We use a finite element method that accounts for magnetic forces, cilia deformation and fluid flow in a fully coupled manner. Mimicking biological cilia, we study magnetic cilia subject to a full range of metachronal driving patterns, including antiplectic, symplectic, laeoplectic and diaplectic waves. We analyse the induced primary flow, secondary flow and mixing rate as a function of the phase lag between cilia and explore the underlying physical mechanism. Our results show that shielding effects between neighboring cilia lead to a primary flow that is larger for antiplectic than for symplectic metachronal waves. The secondary flow can be fully explained by the propagation direction of the metachronal wave. Finally, we show that the mixing rate can be strongly enhanced by laeoplectic and diaplectic metachrony resulting in large velocity gradients and vortex-like flow patterns.}, } @article {pmid35527637, year = {2022}, author = {Gomé, S and Tuckerman, LS and Barkley, D}, title = {Extreme events in transitional turbulence.}, journal = {Philosophical transactions. Series A, Mathematical, physical, and engineering sciences}, volume = {380}, number = {2226}, pages = {20210036}, doi = {10.1098/rsta.2021.0036}, pmid = {35527637}, issn = {1471-2962}, abstract = {Transitional localized turbulence in shear flows is known to either decay to an absorbing laminar state or to proliferate via splitting. The average passage times from one state to the other depend super-exponentially on the Reynolds number and lead to a crossing Reynolds number above which proliferation is more likely than decay. In this paper, we apply a rare-event algorithm, Adaptative Multilevel Splitting, to the deterministic Navier-Stokes equations to study transition paths and estimate large passage times in channel flow more efficiently than direct simulations. We establish a connection with extreme value distributions and show that transition between states is mediated by a regime that is self-similar with the Reynolds number. The super-exponential variation of the passage times is linked to the Reynolds number dependence of the parameters of the extreme value distribution. Finally, motivated by instantons from Large Deviation theory, we show that decay or splitting events approach a most-probable pathway. This article is part of the theme issue 'Mathematical problems in physical fluid dynamics (part 2)'.}, } @article {pmid35527633, year = {2022}, author = {Drivas, TD}, title = {Self-regularization in turbulence from the Kolmogorov 4/5-law and alignment.}, journal = {Philosophical transactions. Series A, Mathematical, physical, and engineering sciences}, volume = {380}, number = {2226}, pages = {20210033}, doi = {10.1098/rsta.2021.0033}, pmid = {35527633}, issn = {1471-2962}, abstract = {A defining feature of three-dimensional hydrodynamic turbulence is that the rate of energy dissipation is bounded away from zero as viscosity is decreased (Reynolds number increased). This phenomenon-anomalous dissipation-is sometimes called the 'zeroth law of turbulence' as it underpins many celebrated theoretical predictions. Another robust feature observed in turbulence is that velocity structure functions [Formula: see text] exhibit persistent power-law scaling in the inertial range, namely [Formula: see text] for exponents [Formula: see text] over an ever increasing (with Reynolds) range of scales. This behaviour indicates that the velocity field retains some fractional differentiability uniformly in the Reynolds number. The Kolmogorov 1941 theory of turbulence predicts that [Formula: see text] for all [Formula: see text] and Onsager's 1949 theory establishes the requirement that [Formula: see text] for [Formula: see text] for consistency with the zeroth law. Empirically, [Formula: see text] and [Formula: see text], suggesting that turbulent Navier-Stokes solutions approximate dissipative weak solutions of the Euler equations possessing (nearly) the minimal degree of singularity required to sustain anomalous dissipation. In this note, we adopt an experimentally supported hypothesis on the anti-alignment of velocity increments with their separation vectors and demonstrate that the inertial dissipation provides a regularization mechanism via the Kolmogorov 4/5-law. This article is part of the theme issue 'Mathematical problems in physical fluid dynamics (part 2)'.}, } @article {pmid35527631, year = {2022}, author = {Parente, E and Farano, M and Robinet, JC and De Palma, P and Cherubini, S}, title = {Continuing invariant solutions towards the turbulent flow.}, journal = {Philosophical transactions. Series A, Mathematical, physical, and engineering sciences}, volume = {380}, number = {2226}, pages = {20210031}, doi = {10.1098/rsta.2021.0031}, pmid = {35527631}, issn = {1471-2962}, abstract = {A new mathematical framework is proposed for characterizing the coherent motion of fluctuations around a mean turbulent channel flow. We search for statistically invariant coherent solutions of the unsteady Reynolds-averaged Navier-Stokes equations written in a perturbative form with respect to the turbulent mean flow, using a suitable approximation of the Reynolds stress tensor. This is achieved by setting up a continuation procedure of known solutions of the perturbative Navier-Stokes equations, based on the continuous increase of the turbulent eddy viscosity towards its turbulent value. The recovered solutions, being sustained only in the presence of the Reynolds stress tensor, are representative of the statistically coherent motion of turbulent flows. For small friction Reynolds number and/or domain size, the statistically invariant motion is almost identical to the corresponding invariant solution of the Navier-Stokes equations. Whereas, for sufficiently large friction number and/or domain size, it considerably departs from the starting invariant solution of the Navier-Stokes equations, presenting spatial structures, main wavelengths and scaling very close to those characterizing both large- and small-scale motion of turbulent channel flows. This article is part of the theme issue 'Mathematical problems in physical fluid dynamics (part 2)'.}, } @article {pmid35523801, year = {2022}, author = {Tretola, G and Vogiatzaki, K}, title = {Unveiling the dynamics of ultra high velocity droplet impact on solid surfaces.}, journal = {Scientific reports}, volume = {12}, number = {1}, pages = {7416}, pmid = {35523801}, issn = {2045-2322}, support = {EP/S001824/1//Engineering and Physical Sciences Research Council/ ; EP/S001824/1//Engineering and Physical Sciences Research Council/ ; }, abstract = {The impact of a liquid droplet onto a solid surface is a phenomenon present in a wide range of natural processes and technological applications. In this study, we focus on impact conditions characterised by ultra high velocities (up to 500 m/s), to investigate-for the first time-how the impact dynamics change when the compressibility of the liquid in the droplet is no longer negligible. A water droplet impacting a dry substrate at four different velocities, from 50 to 500 m/s, is simulated. Such conditions are particularly relevant to aviation as well as industrial gas turbine engine risk management. Thus, numerical investigations as the one we present here provide a powerful tool to analyse the process. We find that increasing the impact velocity changes the flow field within and outside the droplet the moment that the compressibility can no longer be neglected, with the rise of pressure fronts in both regions. Increasing the impact velocity, the compressibility affects also the lamella formed and changes its ejection velocity observed over time (and thus the wetting behaviour) when the region shift from incompressible to compressible. Moreover, it is found that the maximum pressure observed at the wall during the impact is located at the corner of the impact, where the lamella is ejected, not in the centre, and it is influenced by the initial velocity. To predict the maximum pressure experienced by the surface during the high velocity impact, we propose a correlation based on the initial Weber and Reynolds number of the droplet. The complexity and the scales of the dynamics involved in the ultra-high velocity impact is limiting the experimental and analytical studies. To the best of our knowledge there are no experimental data currently available at such conditions. In this study, through numerical simulations, new insights about the impact dynamics at such conditions are provided.}, } @article {pmid35523157, year = {2022}, author = {D'Adamo, J and Collaud, M and Sosa, R and Godoy-Diana, R}, title = {Wake and aeroelasticity of a flexible pitching foil.}, journal = {Bioinspiration & biomimetics}, volume = {17}, number = {4}, pages = {}, doi = {10.1088/1748-3190/ac6d96}, pmid = {35523157}, issn = {1748-3190}, abstract = {A flexible foil undergoing pitching oscillations is studied experimentally in a wind tunnel with different imposed free stream velocities. The chord-based Reynolds number is in the range 1600-4000, such that the dynamics of the system is governed by inertial forces and the wake behind the foil exhibits the reverse Bénard-von Kármán vortex street characteristic of flapping-based propulsion. Particle image velocimetry (PIV) measurements are performed to examine the flow around the foil, whilst the deformation of the foil is also tracked. The first natural frequency of vibration of the foil is within the range of flapping frequencies explored, determining a strongly-coupled dynamics between the elastic foil deformation and the vortex shedding. Cluster-based reduced order modelling is applied on the PIV data in order to identify the coherent flow structures. Analysing the foil kinematics and using a control-volume calculation of the average drag forces from the corresponding velocity fields, we determine the optimal flapping configurations for thrust generation. We show that propulsive force peaks occur at dimensionless frequencies shifted with respect to the elastic resonances that are marked by maximum trailing edge oscillation amplitudes. The thrust peaks are better explained by a wake resonance, which we examine using the tools of classic hydrodynamic stability on the mean propulsive jet profiles.}, } @article {pmid35522515, year = {2022}, author = {Schindler, F and Eckert, S and Zürner, T and Schumacher, J and Vogt, T}, title = {Collapse of Coherent Large Scale Flow in Strongly Turbulent Liquid Metal Convection.}, journal = {Physical review letters}, volume = {128}, number = {16}, pages = {164501}, doi = {10.1103/PhysRevLett.128.164501}, pmid = {35522515}, issn = {1079-7114}, abstract = {The large-scale flow structure and the turbulent transfer of heat and momentum are directly measured in highly turbulent liquid metal convection experiments for Rayleigh numbers varied between 4×10^{5} and ≤5×10^{9} and Prandtl numbers of 0.025≤Pr≤0.033. Our measurements are performed in two cylindrical samples of aspect ratios Γ=diameter/height=0.5 and 1 filled with the eutectic alloy GaInSn. The reconstruction of the three-dimensional flow pattern by 17 ultrasound Doppler velocimetry sensors detecting the velocity profiles along their beam lines in different planes reveals a clear breakdown of coherence of the large-scale circulation for Γ=0.5. As a consequence, the scaling laws for heat and momentum transfer inherit a dependence on the aspect ratio. We show that this breakdown of coherence is accompanied with a reduction of the Reynolds number Re. The scaling exponent β of the power law Nu∝Ra^{β} crosses eventually over from β=0.221 to 0.124 when the liquid metal flow at Γ=0.5 reaches Ra≳2×10^{8} and the coherent large-scale flow is completely collapsed.}, } @article {pmid35512019, year = {2022}, author = {Fei, L and Qin, F and Zhao, J and Derome, D and Carmeliet, J}, title = {Pore-Scale Study on Convective Drying of Porous Media.}, journal = {Langmuir : the ACS journal of surfaces and colloids}, volume = {38}, number = {19}, pages = {6023-6035}, doi = {10.1021/acs.langmuir.2c00267}, pmid = {35512019}, issn = {1520-5827}, abstract = {In this work, a numerical model for isothermal liquid-vapor phase change (evaporation) of the two-component air-water system is proposed based on the pseudopotential lattice Boltzmann method. Through the Chapman-Enskog multiscale analysis, we show that the model can correctly recover the macroscopic governing equations of the multicomponent multiphase system with a built-in binary diffusion mechanism. The model is verified based on the two-component Stefan problem where the measured binary diffusivity is consistent with theoretical analysis. The model is then applied to convective drying of a dual-porosity porous medium at the pore scale. The simulation captures a classical transition in the drying process of porous media, from the constant rate period (CRP, first phase) showing significant capillary pumping from large to small pores, to the falling rate period (FRP, second phase) with the liquid front receding in small pores. It is found that, in the CRP, the evaporation rate increases with the inflow Reynolds number (Re), while in the FRP, the evaporation curves almost collapse at different Res. The underlying mechanism is elucidated by introducing an effective Péclet number (Pe). It is shown that convection is dominant in the CRP and diffusion in the FRP, as evidenced by Pe > 1 and Pe < 1, respectively. We also find a log-law dependence of the average evaporation rate on the inflow Re in the CRP regime. The present work provides new insights into the drying physics of porous media and its direct modeling at the pore scale.}, } @article {pmid35493567, year = {2021}, author = {Salari, A and Appak-Baskoy, S and Coe, IR and Tsai, SSH and Kolios, MC}, title = {An ultrafast enzyme-free acoustic technique for detaching adhered cells in microchannels.}, journal = {RSC advances}, volume = {11}, number = {52}, pages = {32824-32829}, pmid = {35493567}, issn = {2046-2069}, abstract = {Adherent cultured cells are widely used biological tools for a variety of biochemical and biotechnology applications, including drug screening and gene expression analysis. One critical step in culturing adherent cells is the dissociation of cell monolayers into single-cell suspensions. Different enzymatic and non-enzymatic methods have been proposed for this purpose. Trypsinization, the most common enzymatic method for dislodging adhered cells, can be detrimental to cells, as it can damage cell membranes and ultimately cause cell death. Additionally, all available techniques require a prolonged treatment duration, typically on the order of minutes (5-10 min). Dissociation of cells becomes even more challenging in microfluidic devices, where, due to the nature of low Reynolds number flow and reduced mixing efficiency, multiple washing steps and prolonged trypsinization may be necessary to treat all cells. Here, we report a novel acoustofluidic method for the detachment of cells adhered onto a microchannel surface without exposing the cells to any enzymatic or non-enzymatic chemicals. This method enables a rapid (i.e., on the order of seconds), cost-effective, and easy-to-operate cell detachment strategy, yielding a detachment efficiency of ∼99% and cellular viability similar to that of the conventional trypsinization method. Also, as opposed to biochemical-based techniques (e.g., enzymatic), in our approach, cells are exposed to the dissociating agent (i.e., substrate-mediated acoustic excitation and microstreaming flow) only for as long as they remain attached to the substrate. After dissociation, the effect of acoustic excitation is reduced to microstreaming flow, therefore, minimizing unwanted effects of the dissociating agent on the cell phenotype. Additionally, our results suggest that cell excitation at acoustic powers lower than that required for complete cell detachment can potentially be employed for probing the adhesion strength of cell-substrate attachment. This novel approach can, therefore, be used for a wide range of lab-on-a-chip applications.}, } @article {pmid35489898, year = {2022}, author = {Das, A and Styslinger, M and Harris, DM and Zenit, R}, title = {Force and torque-free helical tail robot to study low Reynolds number micro-organism swimming.}, journal = {The Review of scientific instruments}, volume = {93}, number = {4}, pages = {044103}, doi = {10.1063/5.0079815}, pmid = {35489898}, issn = {1089-7623}, mesh = {Models, Biological ; *Robotics ; *Swimming/physiology ; Torque ; Viscosity ; }, abstract = {Helical propulsion is used by many micro-organisms to swim in viscous-dominated environments. Their swimming dynamics are relatively well understood, but a detailed study of the flow fields is still needed to understand wall effects and hydrodynamic interactions among swimmers. In this letter, we describe the development of an autonomous swimming robot with a helical tail that operates in the Stokes regime. The device uses a battery-based power system with a miniature motor that imposes a rotational speed on a helical tail. The speed, direction, and activation are controlled electronically using an infrared remote control. Since the robot is about 5 cm long, we use highly viscous fluids to match the Reynolds number, Re, to be less than 0.1. Measurements of swimming speeds are conducted for a range of helical wavelengths, λ, head geometries, and rotation rates, ω. We provide comparisons of the experimental measurements with analytical predictions derived from resistive force theory. This force and torque-free neutrally buoyant swimmer mimics the swimming strategy of bacteria more closely than previously used designs and offers a lot of potential for future applications.}, } @article {pmid35489862, year = {2022}, author = {Prasad, V and Kulkarni, SS and Sharma, A}, title = {Chaotic advection in a recirculating flow: Effect of a fluid-flexible-solid interaction.}, journal = {Chaos (Woodbury, N.Y.)}, volume = {32}, number = {4}, pages = {043122}, doi = {10.1063/5.0079141}, pmid = {35489862}, issn = {1089-7682}, abstract = {The present work is on laminar recirculating flow-induced deformation as well as motion of a neutrally buoyant flexible elliptical solid, resulting in Lagrangian chaos in a two-dimensional lid-driven cavity flow. Using a fully Eulerian and monolithic approach-based single-solver for the fluid flow and flexible-solid deformation, a chaotic advection study is presented for various aspect ratios β (=0.5-1.0) and a constant volume fraction Φ=10% of an elliptical solid at a constant Ericksen number Er=0.05 and Reynolds number Re=100. Our initial analysis reveals maximum chaotic advection at β=0.5 for which a comprehensive nonlinear dynamical analysis is presented. The Poincaré map revealed elliptic islands and chaotic sea in the fluid flow. Three large elliptic islands, apart from certain smaller islands, were identified near the solid. Periodic point analysis revealed the lowest order hyperbolic/elliptic periodic points to be three. Adaptive material tracking gave a physical picture of a deforming material blob revealing its exponential stretch along with steep folds and demonstrated unstable/stable manifolds corresponding to lowest order hyperbolic points. Furthermore, adaptive material tracking demonstrates heteroclinic connections and tangles in the system that confirm the existence of chaos. For the transient as compared to the periodic flow, adaptive material tracking demonstrates a larger exponential increase of the blob's interfacial area. The finite-time Lyapunov exponent field revealed attracting/repelling Lagrangian coherent structures and entrapped fluid zones. Our work demonstrates an immersed deformable solid-based onset of chaotic advection, for the first time in the literature, which is relevant to a wide range of applications.}, } @article {pmid35487201, year = {2022}, author = {Akanyeti, O and Di Santo, V and Goerig, E and Wainwright, DK and Liao, JC and Castro-Santos, T and Lauder, GV}, title = {Fish-inspired segment models for undulatory steady swimming.}, journal = {Bioinspiration & biomimetics}, volume = {17}, number = {4}, pages = {}, doi = {10.1088/1748-3190/ac6bd6}, pmid = {35487201}, issn = {1748-3190}, support = {R01 DC010809/DC/NIDCD NIH HHS/United States ; }, mesh = {Animals ; Biological Evolution ; Biomechanical Phenomena/physiology ; *Fishes/physiology ; Hydrodynamics ; *Swimming/physiology ; }, abstract = {Many aquatic animals swim by undulatory body movements and understanding the diversity of these movements could unlock the potential for designing better underwater robots. Here, we analyzed the steady swimming kinematics of a diverse group of fish species to investigate whether their undulatory movements can be represented using a series of interconnected multi-segment models, and if so, to identify the key factors driving the segment configuration of the models. Our results show that the steady swimming kinematics of fishes can be described successfully using parsimonious models, 83% of which had fewer than five segments. In these models, the anterior segments were significantly longer than the posterior segments, and there was a direct link between segment configuration and swimming kinematics, body shape, and Reynolds number. The models representing eel-like fishes with elongated bodies and fishes swimming at high Reynolds numbers had more segments and less segment length variability along the body than the models representing other fishes. These fishes recruited their anterior bodies to a greater extent, initiating the undulatory wave more anteriorly. Two shape parameters, related to axial and overall body thickness, predicted segment configuration with moderate to high success rate. We found that head morphology was a good predictor of its segment length. While there was a large variation in head segments, the length of tail segments was similar across all models. Given that fishes exhibited variable caudal fin shapes, the consistency of tail segments could be a result of an evolutionary constraint tuned for high propulsive efficiency. The bio-inspired multi-segment models presented in this study highlight the key bending points along the body and can be used to decide on the placement of actuators in fish-inspired robots, to model hydrodynamic forces in theoretical and computational studies, or for predicting muscle activation patterns during swimming.}, } @article {pmid35481832, year = {2022}, author = {Hu, S and Zhang, J and Shelley, MJ}, title = {Enhanced clamshell swimming with asymmetric beating at low Reynolds number.}, journal = {Soft matter}, volume = {18}, number = {18}, pages = {3605-3612}, doi = {10.1039/d2sm00292b}, pmid = {35481832}, issn = {1744-6848}, abstract = {A single flexible filament can be actuated to escape from the scallop theorem and generate net propulsion at low Reynolds number. In this work, we study the dynamics of a simple boundary-driven multi-filament swimmer, a two-arm clamshell actuated at the hinged point, using a nonlocal slender body approximation with hydrodynamic interactions. We first consider an elastic clamshell consisted of flexible filaments with intrinsic curvature, and then build segmental models consisted of rigid segments connected by different mechanical joints with different forms of response torques. The simplicity of the system allows us to fully explore the effect of various parameters on the swimming performance. Optimal included angles and elastoviscous numbers are identified. The segmental models capture the characteristic dynamics of the elastic clamshell. We further demonstrate how the swimming performance can be significantly enhanced by the asymmetric beating patterns induced by biased torques.}, } @article {pmid35478056, year = {2022}, author = {Kotnurkar, A and Kallolikar, N}, title = {Effect of Joule heating and entropy generation on multi-slip condition of peristaltic flow of Casson nanofluid in an asymmetric channel.}, journal = {Journal of biological physics}, volume = {}, number = {}, pages = {}, pmid = {35478056}, issn = {1573-0689}, abstract = {In the present investigation, the effect of multi-slip condition on peristaltic flow through asymmetric channel with Joule heating effect is considered. We also considered the incompressible non-Newtonian Casson nanofluid model for blood, which is electrically conducting. Second law of thermodynamics is used to examine the entropy generation. Multi-slip condition is used at the boundary of the wall and the analysis is also restricted under the low Reynolds number and long wavelength assumption. The governing equations were transformed into a non-dimensional form by using suitable terms. The reduced non-dimensional highly nonlinear partial differential equations are solved by using the Homotopy Perturbation Sumudu transformation method (HPSTM). The influence of different physical parameters on dimensionless velocity, pressure gradient, temperature, concentration and nanoparticle is graphically presented. From the results, one can understand that the Joule heating effect controls the heat transfer in the system and as the magnetic parameter is increased, there will be decay in the velocity of fluid. The outcomes of the present investigation can be applicable in examining the chyme motion in the gastrointestinal tract and controlling the blood flow during surgery. Present study shows an excellent agreement with the previously available studies in the limiting case.}, } @article {pmid35460986, year = {2022}, author = {Liu, J and Yang, Z and Li, M and Lu, K and Li, D}, title = {Evaluating the concrete grade-control structures built by modified fish-nest bricks in the river restoration: A lab-based case study.}, journal = {Journal of environmental management}, volume = {314}, number = {}, pages = {115056}, doi = {10.1016/j.jenvman.2022.115056}, pmid = {35460986}, issn = {1095-8630}, mesh = {Animals ; Ecosystem ; *Fishes ; *Rivers ; Water ; }, abstract = {Concrete grade-control structures (CGCSs) have broad application prospects in the restoration of large rivers. But there is a lack of indicators to evaluate CGCSs at laboratory study. In this study, we proposed two evaluation indicators from the perspective of the impact of CGCSs on geomorphology change and fish habitat, namely the spatial-averaged occurrence probability of sweep events near the bed and flow diversity. To verify the reasonableness of these indicators, flume experiments were conducted with CGCSs built by modified fish-nest bricks in different Reynolds number and layout condition. Data of the flow field around structures in streamwise, transverse and vertical direction was obtained and analyzed. Results of mean flow field show that large recirculation zones are found in the cavity and behind the element. The mechanism of suspended sediment deposition around CGCSs in the flow can be further clarified by combining sweep and ejection according to quadrant analysis. In the vertical direction, the ratio of sweep to total events near bed after spatial-averaged processing is found to be higher for the staggered array. According to the Shannon's entropy, water flow diversity was calculated to quantify the fish habitat. The water flow diversity index around the CGCSs is higher for the staggered. It can be concluded that the elements of CGCSs in staggered manners have a better protection for riverbed and can provide a more stable fish habitat suitability. The results anticipated by the spatial-averaged occurrence probability of sweep events near bed and flow diversity in the experiment are consistent with the result of previous research on landform change and fish habitat. The research could provide a theoretical basis for the application of CGCSs for river restoration.}, } @article {pmid35457904, year = {2022}, author = {Martin, E and Valeije, A and Sastre, F and Velazquez, A}, title = {Impact of Channels Aspect Ratio on the Heat Transfer in Finned Heat Sinks with Tip Clearance.}, journal = {Micromachines}, volume = {13}, number = {4}, pages = {}, pmid = {35457904}, issn = {2072-666X}, abstract = {A 3D numerical study is used to analyze the flow topology and performance, in terms of heat transfer efficiency and required pumping power, of heat sink devices with different channel aspect-ratio in the presence of tip-clearance. Seven different channel aspect ratios AR, from 0.25 to 1.75, were analyzed. The flow Reynolds numbers Re, based on the average velocity evaluated in the device channels region, were in the range of 200 to 1000. Two different behaviors of the global Nusselt were obtained depending on the flow Reynolds number: for Re<600, the heat transfer increased with the channels aspect ratio, e.g., for Re=400, the global Nusselt number increased by 14% for configuration AR=1.75 when compared to configuration AR=0.25. For Re>600, the maximum Nusselt is obtained for the squared-channel configuration, and, for some configurations, flow destabilization to a unsteady regime appeared. For Re=700, Nusselt number reduced when compared with the squared-channel device, 11% and 2% for configurations with AR=0.25 and 1.75, respectively. Dimensionless pressure drop decreased with the aspect ratio for all cases. In the context of micro-devices, where the Reynolds number is small, these results indicate that the use of channels with high aspect-ratios is more beneficial, both in terms of thermal and dynamic efficiency.}, } @article {pmid35454454, year = {2022}, author = {Ayub, R and Ahmad, S and Ahmad, S and Akhtar, Y and Alam, MM and Mahmoud, O}, title = {Numerical Assessment of Dipole Interaction with the Single-Phase Nanofluid Flow in an Enclosure: A Pseudo-Transient Approach.}, journal = {Materials (Basel, Switzerland)}, volume = {15}, number = {8}, pages = {}, pmid = {35454454}, issn = {1996-1944}, abstract = {Nanofluids substantially enhance the physical and thermal characteristics of the base or conducting fluids specifically when interacting with the magnetic field. Several engineering processes like geothermal energy extraction, metal casting, nuclear reactor coolers, nuclear fusion, magnetohydrodynamics flow meters, petrochemicals, and pumps incorporate magnetic field interaction with the nanofluids. On the other hand, an enhancement in heat transfer due to nanofluids is essentially required in various thermal systems. The goal of this study is to figure out that how much a magnetic field affects nanofluid flow in an enclosure because of a dipole. The nanofluid is characterized using a single-phase model, and the governing partial differential equations are computed numerically. A Pseudo time based numerical algorithm is developed to numerically solve the problem. It can be deduced that the Reynolds number and the magnetic parameter have a low effect on the Nusselt number and skin friction. The Nusselt number rises near the dipole location because of an increase in the magnetic parameter Mn and the Reynolds number Re. The imposed magnetic field alters the region of high temperature nearby the dipole, while newly generated vortices rotate in alternate directions. Furthermore, nanoparticle volume fraction causes a slight change in the skin friction while it marginally reduces the Nusselt number.}, } @article {pmid35448318, year = {2022}, author = {Chandrasekaran, AS and Fix, AJ and Warsinger, DM}, title = {Combined Membrane Dehumidification with Heat Exchangers Optimized Using CFD for High Efficiency HVAC Systems.}, journal = {Membranes}, volume = {12}, number = {4}, pages = {}, pmid = {35448318}, issn = {2077-0375}, support = {CHPB-50-2020//Purdue Center for High Performance Buildings/ ; }, abstract = {Traditional air conditioning systems use a significant amount of energy on dehumidification by condensing water vapor out from the air. Membrane-based air conditioning systems help overcome this problem by avoiding condensation and treating the sensible and latent loads separately, using membranes that allow water vapor transport, but not air (nitrogen and oxygen). In this work, a computational fluid dynamics (CFD) model has been developed to predict the heat and mass transfer and concentration polarization performance of a novel active membrane-based energy exchanger (AMX). The novel design is the first of its kind to integrate both vapor removal via membranes and air cooling into one device. The heat transfer results from the CFD simulations are compared with common empirical correlations for similar geometries. The performance of the AMX is studied over a broad range of operating conditions using the compared CFD model. The results show that strong tradeoffs result in optimal values for the channel length (0.6-0.8 m) and the ratio of coil diameter to channel height (~0.5). Water vapor transport is best if the flow is just past the turbulence transition around 3000-5000 Reynolds number. These trends hold over a range of conditions and dimensions.}, } @article {pmid35446443, year = {2022}, author = {Torres-Saucedo, OL and Morales-Cruzado, B and Pérez-Guitérrez, FG}, title = {Experimental determination of shear stresses on an artificial transcoelomic metastasis model using optical tweezers: A comparison with numerical simulation.}, journal = {Lasers in surgery and medicine}, volume = {}, number = {}, pages = {}, doi = {10.1002/lsm.23554}, pmid = {35446443}, issn = {1096-9101}, support = {A1-S-9887//Consejo Nacional de Ciencia y Tecnología/ ; CF-2019-102986//Consejo Nacional de Ciencia y Tecnología/ ; }, abstract = {BACKGROUND: One of the reported pathways of cancer spread is the transcoelomic pathway, which is understood as the spread of cancer cells in the abdominal and thoracic cavities through interstitial fluid. It has been proven that the shear stresses caused by microfluidic currents on cancer tumors in the abdominal and thoracic cavities cause the detachment of cancer cells triggering transcoelomic metastasis; however, the magnitude of shear stresses has not yet been measured experimentally.

OBJECTIVES: The objective of this study is to develop an experimental methodology using optical tweezers to approximate the shear stresses suffered by a nonporous, rigid artificial cancerous nodule model.

METHODS: Artificial cancerous nodule model was made by the agglomeration of 2 μm diameter polystyrene particles in a microfluidic platform. Optical tweezers were used as a velocimetry tool and shear stresses on the surface of the nodule model were approximated with the viscous shear stress equation. The results were verified with a numerical simulation performed in Ansys Fluent.

RESULTS: Shear stress originated by microflow over artificial cancerous nodule model were quantified both experimentally and numerically, showing good agreement between both methods. Such stress on the nodules' surface was much greater than that suffered by the wall on which the nodule model was located and dependent of the nodule model geometry. Although the experiment and simulation of this study were performed using a rigid and nonporous nodule model, the conclusion obtained about the increase of shear stresses applies to permeable, porous, and soft nodules as well, because the shear stresses are associated to the acceleration of the fluid originated by the reduction of the cross-sectional area.

CONCLUSIONS: Shear stress over artificial nodule model were successfully quantified using optical tweezer-based velocimetry technique and verified through numerical calculation. Advantages of experimental technique are: (1) it allows to control the position in a three-dimensional plane, allowing measurements in the vicinity of the analyzed surfaces, and (2) it is applicable for very low Reynolds number (Re « 1). On the other hand, as disadvantages: (1) it tends to be complicated to perform velocity measurements over obstacles and (2) it is limited in trapping distance.}, } @article {pmid35436159, year = {2022}, author = {Ibrahim, MG}, title = {Numerical simulation to the activation energy study on blood flow of seminal nanofluid with mixed convection effects.}, journal = {Computer methods in biomechanics and biomedical engineering}, volume = {}, number = {}, pages = {1-11}, doi = {10.1080/10255842.2022.2063018}, pmid = {35436159}, issn = {1476-8259}, abstract = {This study sheds light on the influences of Arrhenius activation energy and variable velocity slip on MHD blood motion of Seminal nanofluid in a vertical symmetric channel. In addition, mixed convection, hall current and thermal jump are taken into consideration. The governing system of differential equations with highly nonlinear terms is simplified with facts of long wavelength and low Reynolds number. Pade' approximant and differential transform techniques are combined mathematically to obtain the semi-numerical solutions for the governing system of PDEs. The results are computed and verified graphically with aid of Mathematica 12.3. Physical parameters considered are studied in detail sketchily for the proposed model. Verification/signification of results is approved semi-numerically by comparing the prior results by the newest existing published results by Ahmad et al 2021. Results show that, Velocity of seminal fluid is diminishes with a rise in viscosity-dependent parameter that is a significant feature which can be utilized in controlling the transport of spermatozoa into the cervical canal.}, } @article {pmid35428793, year = {2022}, author = {Koo, D and So, H}, title = {Facile microfabrication of three dimensional-patterned micromixers using additive manufacturing technology.}, journal = {Scientific reports}, volume = {12}, number = {1}, pages = {6346}, pmid = {35428793}, issn = {2045-2322}, mesh = {Computer Simulation ; Equipment Design ; *Lab-On-A-Chip Devices ; *Microtechnology ; Printing, Three-Dimensional ; }, abstract = {This study investigates the manufacturing method of oblique patterns in microchannels and the effect of these patterns on mixing performance in microchannels. To fabricate three-dimensional (3D) and oblique patterns in microchannels, 3D printing and replica methods were utilized to mold patterns and microchannels, respectively. The angle and size of the patterns were controlled by the printing angle and resolution, respectively. The mixing efficiency was experimentally characterized, and the mixing principle was analyzed using computational fluid dynamics simulation. The analysis showed that the mixing channel cast from the mold printed with a printing angle of 30° and resolution of 300 μm exhibited the best mixing efficiency with a segregation index of approximately 0.05 at a Reynolds number of 5.4. This was because, as the patterns inside the microchannel were more oblique, "split" and "recombine" behaviors between two fluids were enhanced owing to the geometrical effect. This study supports the use of the 3D printing method to create unique patterns inside microchannels and improve the mixing performance of two laminar flows for various applications such as point-of-care diagnostics, lab-on-a-chip, and chemical synthesis.}, } @article {pmid35428381, year = {2022}, author = {Ilg, P}, title = {Multiparticle collision dynamics for ferrofluids.}, journal = {The Journal of chemical physics}, volume = {156}, number = {14}, pages = {144905}, doi = {10.1063/5.0087981}, pmid = {35428381}, issn = {1089-7690}, abstract = {Detailed studies of the intriguing field-dependent dynamics and transport properties of confined flowing ferrofluids require efficient mesoscopic simulation methods that account for fluctuating ferrohydrodynamics. Here, we propose such a new mesoscopic model for the dynamics and flow of ferrofluids, where we couple the multi-particle collision dynamics method as a solver for the fluctuating hydrodynamics equations to the stochastic magnetization dynamics of suspended magnetic nanoparticles. This hybrid model is validated by reproducing the magnetoviscous effect in Poiseuille flow, obtaining the rotational viscosity in quantitative agreement with theoretical predictions. We also illustrate the new method for the benchmark problem of flow around a square cylinder. Interestingly, we observe that the length of the recirculation region is increased, whereas the drag coefficient is decreased in ferrofluids when an external magnetic field is applied compared with the field-free case at the same effective Reynolds number. The presence of thermal fluctuations and the flexibility of this particle-based mesoscopic method provide a promising tool to investigate a broad range of flow phenomena of magnetic fluids, and the method could also serve as an efficient way to simulate solvent effects when colloidal particles are immersed in ferrofluids.}, } @article {pmid35428147, year = {2022}, author = {Nagy, PT}, title = {Enstrophy change of the Reynolds-Orr solution in channel flow.}, journal = {Physical review. E}, volume = {105}, number = {3-2}, pages = {035108}, doi = {10.1103/PhysRevE.105.035108}, pmid = {35428147}, issn = {2470-0053}, abstract = {The plane Poiseuille flow is one of the elementary flow configurations. Although its laminar-turbulent transition mechanism has been investigated intensively in the last century, the significant difference in the critical Reynolds number between the experiments and the theory lacks a clear explanation. In this paper, an attempt is made to reduce this gap by analyzing the solution of the Reynolds-Orr equation. Recent published results have shown that the usage of enstrophy (the volume integral of the squared vorticity) instead of the kinetic energy as the norm of perturbations predicts higher Reynolds numbers in the two-dimensional case. In addition, other research show has shown an improvement of the original Reynolds-Orr energy equation using the weighted norm in a tilted coordinate system. In this paper the enstrophy is used in three dimensions combined with the tilted coordinate system approach. The zero-enstrophy-growth constraint is applied to the classical Reynolds-Orr equation, and then the solution is further refined in the tilted coordinate system. The results are compared to direct numerical simulations published previously.}, } @article {pmid35428113, year = {2022}, author = {Steiros, K}, title = {Balanced nonstationary turbulence.}, journal = {Physical review. E}, volume = {105}, number = {3-2}, pages = {035109}, doi = {10.1103/PhysRevE.105.035109}, pmid = {35428113}, issn = {2470-0053}, abstract = {Kolmogorov's 1941 (K41) framework remains central to the understanding of turbulent flows. However, in unsteady turbulence, K41's critical equilibrium assumption is expected to hold in an asymptotic manner, as the Reynolds number and wave numbers tend to infinity, rendering K41 not strictly valid at finite wave numbers. This work proposes a generalization of K41 for out-of-equilibrium effects and cascades far from initial conditions. The main result is a correction to the -5/3 law for out-of-equilibrium eddies, unrelated to intermittency effects. Experimental and numerical evidence is provided in support of the theoretical results.}, } @article {pmid35428103, year = {2022}, author = {Rana, N and Perlekar, P}, title = {Phase ordering, topological defects, and turbulence in the three-dimensional incompressible Toner-Tu equation.}, journal = {Physical review. E}, volume = {105}, number = {3}, pages = {L032603}, doi = {10.1103/PhysRevE.105.L032603}, pmid = {35428103}, issn = {2470-0053}, abstract = {We investigate the phase-ordering dynamics of the incompressible Toner-Tu equation in three dimensions. We show that the phase ordering proceeds via defect merger events and the dynamics is controlled by the Reynolds number Re. At low Re, the dynamics is similar to that of the Ginzburg-Landau equation. At high Re, turbulence controls phase ordering. In particular, we observe a forward energy cascade from the coarsening length scale to the dissipation scale, clustering of defects, and multiscaling in velocity correlations.}, } @article {pmid35420623, year = {2022}, author = {Thurgood, P and Chheang, C and Needham, S and Pirogova, E and Peter, K and Baratchi, S and Khoshmanesh, K}, title = {Generation of dynamic vortices in a microfluidic system incorporating stenosis barrier by tube oscillation.}, journal = {Lab on a chip}, volume = {22}, number = {10}, pages = {1917-1928}, doi = {10.1039/d2lc00135g}, pmid = {35420623}, issn = {1473-0189}, mesh = {Constriction, Pathologic ; Humans ; *Microfluidics/methods ; }, abstract = {Microfluidic systems incorporating sudden expansions are widely used for generation of vortex flow patterns. However, the formation of vortices requires high flow rates to induce inertial effects. Here, we introduce a new method for generating dynamic vortices in microfluidics at low static flow rates. Human blood is driven through a microfluidic channel incorporating a semi-circular stenosis barrier. The inlet tube of the channel is axially oscillated using a computer-controlled audio-speaker. The tube oscillation induces high transient flow rates in the channel, which generates dynamic vortices across the stenosis barrier. The size of the vortices can be modulated by varying the frequency and amplitude of tube oscillation. Various vortex flow patterns can be generated by varying the flow rate. The formation and size of the vortices can be predicted using the Reynolds number of the oscillating tube. We demonstrate the potential application of the system for investigating the adhesion and phagocytosis of circulating immune cells under pathologically high shear rates induced at the stenosis. This approach facilitates the development of versatile and controllable inertial microfluidic systems for performing various cellular assays while operating at low static flow rates and low sample volumes.}, } @article {pmid35407874, year = {2022}, author = {Behura, AK and Mohanty, CP and Singh, MR and Kumar, A and Linul, E and Rajak, DK}, title = {Performance Analysis of Three Side Roughened Solar Air Heater: A Preliminary Investigation.}, journal = {Materials (Basel, Switzerland)}, volume = {15}, number = {7}, pages = {}, pmid = {35407874}, issn = {1996-1944}, abstract = {In recent years, sunlight has been used in several fields such as photovoltaic cells, flat plate collectors, solar cookers, green buildings, and agricultural applications. Improved thermal performance has been seen which comes of three sides absorber plate with glass cover compared to the traditional one. This paper presents the Nusselt (Nu) number, collector efficiency factor (CEF), and collector heat removal factor (CHRF) for the optimal solution of three sides artificially roughened solar air heater. Five input variables such as Reynolds (Re) number, relative roughness pitch, relative roughness height, mass flow rate, and air temperature of the duct are taken into account for improved efficiency optimization of collector, collector heat removal factor, and Nu number. Technique for order of preference by similarity to ideal solution (TOPSIS) technique is used to identify the best alternative amongst a number of performance measures by converting them into an equivalent single variable. Moreover, the results revealed the high accuracy of the CEF, CHRF, and Nu number of 75-80%, 74-78%, and 63-71%, respectively. Meanwhile, it has been also observed that roughness Re number varies between 12,500 and 13,500, and height of relative roughness is 0.0245, including pitch of relative roughness 10 along with the rate of mass flow is 0.041 kg/s.}, } @article {pmid35407169, year = {2022}, author = {Bhatti, MM and Bég, OA and Abdelsalam, SI}, title = {Computational Framework of Magnetized MgO-Ni/Water-Based Stagnation Nanoflow Past an Elastic Stretching Surface: Application in Solar Energy Coatings.}, journal = {Nanomaterials (Basel, Switzerland)}, volume = {12}, number = {7}, pages = {}, pmid = {35407169}, issn = {2079-4991}, abstract = {In this article, motivated by novel nanofluid solar energy coating systems, a mathematical model of hybrid magnesium oxide (MgO) and nickel (Ni) nanofluid magnetohydrodynamic (MHD) stagnation point flow impinging on a porous elastic stretching surface in a porous medium is developed. The hybrid nanofluid is electrically conducted, and a magnetic Reynolds number is sufficiently large enough to invoke an induced magnetic field. A Darcy model is adopted for the isotropic, homogenous porous medium. The boundary conditions account for the impacts of the velocity slip and thermal slip. Heat generation (source)/absorption (sink) and also viscous dissipation effects are included. The mathematical formulation has been performed with the help of similarity variables, and the resulting coupled nonlinear dimensionless ordinary differential equations have been solved numerically with the help of the shooting method. In order to test the validity of the current results and the convergence of the solutions, a numerical comparison with previously published results is included. Numerical results are plotted for the effect of emerging parameters on velocity, temperature, magnetic induction, skin friction, and Nusselt number. With an increment in nanoparticle volume fraction of both MgO and Ni nanoparticles, the temperature and thermal boundary layer thickness of the nanofluid are elevated. An increase in the porous medium parameter (Darcy number), velocity slip, and thermal Grashof number all enhance the induced magnetic field. Initial increments in the nanoparticle volume fraction for both MgO and Ni suppress the magnetic induction near the wall, although, subsequently, when further from the wall, this effect is reversed. Temperature is enhanced with heat generation, whereas it is depleted with heat absorption and thermal slip effects. Overall, excellent thermal enhancement is achieved by the hybrid nanofluid.}, } @article {pmid35401713, year = {2022}, author = {Fang, L and Li, H and Li, B}, title = {Dynamic Analysis of Deep Water Highway Tunnel under Ocean Current.}, journal = {Computational intelligence and neuroscience}, volume = {2022}, number = {}, pages = {9551792}, pmid = {35401713}, issn = {1687-5273}, abstract = {Comprehensively comparing the merits and demerits of the existing means of transportation across the water, a new underwater transportation structure for crossing the wide water area, named as "deep water highway tunnel" (hereinafter called "DWHT"), is proposed. The characteristics of flow field around the typical section of DWHT at different flow velocities are investigated, which can provide reference for the values of hydrodynamic coefficient at high Reynolds number. The vibration modes and natural by the sound-solid coupling method. In addition, considering the factors of fluid-structure coupling, the dynamic response of displacement and internal force is analyzed based on CFD for the weak parts of the structure. The results show that the deepening of water and the increase of flow will significantly increase the flow field pressure and structure stress, and when the span (or width-span ratio) of the tunnel body extends beyond a certain range, the dynamic characteristics and dynamic response rules of the structure will change.}, } @article {pmid35393485, year = {2022}, author = {Ghorbani, N and Targhi, MZ and Heyhat, MM and Alihosseini, Y}, title = {Investigation of wavy microchannel ability on electronic devices cooling with the case study of choosing the most efficient microchannel pattern.}, journal = {Scientific reports}, volume = {12}, number = {1}, pages = {5882}, pmid = {35393485}, issn = {2045-2322}, abstract = {A numerical study was conducted to investigate the ability of wavy microchannels to damp the temperature fluctuations generates in electronic devices. Five wavy patterns are considered with the amplitude and wavelength in the ranges of 62.5 to 250 μm and 1250 to 5000 μm, respectively to study the effect of governing phenomena of flow within wavy patterns on thermal-hydraulic performance. The flow regime is laminar and the Reynolds number is in the range of 300 to 900, and a relatively high heat flux of 80 W/cm2 is applied to the microchannels substrate. Also, variable flux condition is studied for heat fluxes of 80, 120, 160, 200, and 240 W/cm2 and for the most efficient wavy and straight microchannels. Results showed that the geometries with larger amplitude to wavelength ratio have a lower radius of curvature and larger Dean number, and as a result of transverse flow (secondary flow) amplification, they have enhanced heat transfer. Also, by comparing the ratio of the transverse velocity components to the axial component, it was found that by decreasing the radius of curvature and increasing the Dean number, transverse velocity increases, which intensifies the heat transfer between the wall and the fluid. The appraisement of the performance evaluation criterion (PEC) illustrates that the wavy case with an amplitude of 250 μm and wavelength of 2500 μm is the best geometry from the thermal-hydraulic point of view in the studied range. Finally, with variable flux condition, the wavy microchannel has responded well to the temperature increase and has created a much more uniform surface temperature compared to straight pattern. The proposed wavy pattern ensures that there are no hotspots which could damage the electronic chip. Presented wavy patterns can be used in heat sinks heat transfer enhancement to allow the chip to run in higher heat fluxes.}, } @article {pmid35390073, year = {2022}, author = {Almerol, JLO and Liponhay, MP}, title = {Clustering of fast gyrotactic particles in low-Reynolds-number flow.}, journal = {PloS one}, volume = {17}, number = {4}, pages = {e0266611}, pmid = {35390073}, issn = {1932-6203}, mesh = {Cluster Analysis ; Computer Simulation ; *Hydrodynamics ; Physical Phenomena ; *Swimming ; }, abstract = {Systems of particles in turbulent flows exhibit clustering where particles form patches in certain regions of space. Previous studies have shown that motile particles accumulate inside the vortices and in downwelling regions, while light and heavy non-motile particles accumulate inside and outside the vortices, respectively. While strong clustering is generated in regions of high vorticity, clustering of motile particles is still observed in fluid flows where vortices are short-lived. In this study, we investigate the clustering of fast swimming particles in a low-Reynolds-number turbulent flow and characterize the probability distributions of particle speed and acceleration and their influence on particle clustering. We simulate gyrotactic swimming particles in a cubic system with homogeneous and isotropic turbulent flow. Here, the swimming velocity explored is relatively faster than what has been explored in other reports. The fluid flow is produced by conducting a direct numerical simulation of the Navier-Stokes equation. In contrast with the previous results, our results show that swimming particles can accumulate outside the vortices, and clustering is dictated by the swimming number and is invariant with the stability number. We have also found that highly clustered particles are sufficiently characterized by their acceleration, where the increase in the acceleration frequency distribution of the most clustered particles suggests a direct influence of acceleration on clustering. Furthermore, the acceleration of the most clustered particles resides in acceleration values where a cross-over in the acceleration PDFs are observed, an indicator that particle acceleration generates clustering. Our findings on motile particles clustering can be applied to understanding the behavior of faster natural or artificial swimmers.}, } @article {pmid35389496, year = {2022}, author = {Letendre, F and Cameron, CB}, title = {The capture of crude oil droplets by filter feeders at high and low Reynolds numbers.}, journal = {The Journal of experimental biology}, volume = {225}, number = {8}, pages = {}, doi = {10.1242/jeb.243819}, pmid = {35389496}, issn = {1477-9145}, support = {RGPIN/05058-2017//Natural Sciences and Engineering Research Council of Canada/ ; //Natural Sciences and Engineering Research Council of Canada/ ; }, mesh = {Animals ; Daphnia ; Food Chain ; *Petroleum ; *Petroleum Pollution ; *Thoracica ; }, abstract = {Crustacean filter feeders capture oil droplets with the use of their ramified appendages. These appendages behave as paddles or sieves, based on the system's Reynolds number. Here, we used high-speed videography, scanning electron microscopy and fluid mechanics to study the capturing mechanisms of crude oil droplets and the filtering appendage's wettability by two species of barnacles (Balanus glandula and Balanus crenatus) and of the freshwater cladoceran Daphnia magna. Our results show that barnacle appendages behave as paddles and capture droplets in their boundary layers at low Reynolds number. At high Reynolds number, droplets are most likely to be captured via direct interception. There is an intermediate range of Reynolds number where droplets can be captured by both mechanisms at the same time. Daphnia magna captures droplets in the boundary layers of the third and fourth pair of thoracic legs with a metachronal motion of the appendages. All studied surfaces were revealed to be highly lipophobic, demonstrating captured oil droplets with high contact angles. We also discuss implications of such capture mechanisms and wettability on potential ingestion of crude oil by filter feeders. These results further our understanding of the capture of crude oil by filter feeders, shedding light on the main entry point of oil in marine food webs.}, } @article {pmid35385160, year = {2022}, author = {Wang, J and Dong, Y and Ma, P and Wang, Y and Zhang, F and Cai, B and Chen, P and Liu, BF}, title = {Intelligent Micro/nanorobot for Cancer Theragnostic.}, journal = {Advanced materials (Deerfield Beach, Fla.)}, volume = {}, number = {}, pages = {e2201051}, doi = {10.1002/adma.202201051}, pmid = {35385160}, issn = {1521-4095}, abstract = {Cancer is one of the most intractable diseases owing to its high mortality rate and lack of effective diagnostic and treatment tools. Advancements in micro/nanorobot (MNR)-assisted sensing, imaging, and therapeutics offer unprecedented opportunities to develop MNR-based cancer theragnostic platforms. Unlike ordinary nanoparticles which exhibit Brownian motion in biofluids, MNRs overcome viscous resistance in an ultralow Reynolds number (Re<<1) environment by effective self-propulsion. This unique locomotion property has motivated the advanced design and functionalization of MNRs as a basis for next-generation cancer therapy platforms, which offer the potential for precise distribution and improved permeation of therapeutic agents. Enhanced barrier penetration, imaging-guided operation, and biosensing have additionally been studied to enable the promising cancer-related applications of MNRs. This review comprehensively addresses recent advances in MNR-based cancer therapy, including in actuation engines, diagnostics, medical imaging, and targeted drug delivery; we highlight promising research opportunities that could have a profound impact on cancer therapy over the next decade. This article is protected by copyright. All rights reserved.}, } @article {pmid35379035, year = {2022}, author = {Saeed Khan, MW and Ali, N and Bég, OA}, title = {Thermal entrance problem for blood flow inside an axisymmetric tube: The classical Graetz problem extended for Quemada's bio-rheological fluid with axial conduction.}, journal = {Proceedings of the Institution of Mechanical Engineers. Part H, Journal of engineering in medicine}, volume = {}, number = {}, pages = {9544119221086479}, doi = {10.1177/09544119221086479}, pmid = {35379035}, issn = {2041-3033}, abstract = {The heat-conducting nature of blood is critical in the human circulatory system and features also in important thermal regulation and blood processing systems in biomedicine. Motivated by these applications, in the present investigation, the classical Graetz problem in heat transfer is extended to the case of a bio-rheological fluid model. The Quemada bio-rheological fluid model is selected since it has been shown to be accurate in mimicking physiological flows (blood) at different shear rates and hematocrits. The steady two-dimensional energy equation without viscous dissipation in stationary regime is tackled via a separation of variables approach for the isothermal wall temperature case. Following the introduction of transformation variables, the ensuing dimensionless boundary value problem is solved numerically via MATLAB based algorithm known as bvp5c (a finite difference code that implements the four-stage Lobatto IIIa collocation formula). Numerical validation is also presented against two analytical approaches namely, series solutions and Kummer function techniques. Axial conduction in terms of Péclet number is also considered. Typical values of Reynolds number and Prandtl number are used to categorize the vascular regions. The graphical representation of mean temperature, temperature gradient, and Nusselt numbers along with detail discussions are presented for the effects of Quemada non-Newtonian parameters and Péclet number. The current analysis may also have potential applications for the development of microfluidic and biofluidic devices particularly which are used in the diagnosis of diseases in addition to blood oxygenation technologies.}, } @article {pmid35363001, year = {2022}, author = {Tan, S and Ni, R}, title = {Universality and Intermittency of Pair Dispersion in Turbulence.}, journal = {Physical review letters}, volume = {128}, number = {11}, pages = {114502}, doi = {10.1103/PhysRevLett.128.114502}, pmid = {35363001}, issn = {1079-7114}, abstract = {Turbulence can disperse a concentrated parcel of pollutants at a rate over nine orders of magnitude higher than its purely diffusive counterpart. One intriguing signature of turbulent dispersion is its superdiffusive scaling. However, the universality of this scaling law is still in question. By leveraging a new laboratory facility, particle pairs with small initial separations can be tracked over four decades of separation in time and five decades of separation in squared displacement, thereby observing the full range of dispersion scaling laws. The results show that the classical Richardson cubic scaling will be reached not for an initial separation asymptotically close to zero but at a critical value, and this value does not appear to depend on the Reynolds number, providing an effective way to study universal dispersion dynamics. Additionally, the results agree well with the prediction based on the multifractal model and may help reconcile different reported scaling laws from laboratory experiments and field studies.}, } @article {pmid35355005, year = {2022}, author = {Kamdar, S and Shin, S and Leishangthem, P and Francis, LF and Xu, X and Cheng, X}, title = {The colloidal nature of complex fluids enhances bacterial motility.}, journal = {Nature}, volume = {603}, number = {7903}, pages = {819-823}, pmid = {35355005}, issn = {1476-4687}, mesh = {Bacteria ; *Colloids ; *Ecosystem ; Humans ; Hydrodynamics ; Polymers ; }, abstract = {The natural habitats of microorganisms in the human microbiome, ocean and soil ecosystems are full of colloids and macromolecules. Such environments exhibit non-Newtonian flow properties, drastically affecting the locomotion of microorganisms1-5. Although the low-Reynolds-number hydrodynamics of swimming flagellated bacteria in simple Newtonian fluids has been well developed6-9, our understanding of bacterial motility in complex non-Newtonian fluids is less mature10,11. Even after six decades of research, fundamental questions about the nature and origin of bacterial motility enhancement in polymer solutions are still under debate12-23. Here we show that flagellated bacteria in dilute colloidal suspensions display quantitatively similar motile behaviours to those in dilute polymer solutions, in particular a universal particle-size-dependent motility enhancement up to 80% accompanied by a strong suppression of bacterial wobbling18,24. By virtue of the hard-sphere nature of colloids, whose size and volume fraction we vary across experiments, our results shed light on the long-standing controversy over bacterial motility enhancement in complex fluids and suggest that polymer dynamics may not be essential for capturing the phenomenon12-23. A physical model that incorporates the colloidal nature of complex fluids quantitatively explains bacterial wobbling dynamics and mobility enhancement in both colloidal and polymeric fluids. Our findings contribute to the understanding of motile behaviours of bacteria in complex fluids, which are relevant for a wide range of microbiological processes25 and for engineering bacterial swimming in complex environments26,27.}, } @article {pmid35338884, year = {2022}, author = {Mezali, F and Benmamar, S and Naima, K and Ameur, H and Rafik, O}, title = {Evaluation of stent effect and thrombosis generation with different blood rheology on an intracranial aneurysm by the Lattice Boltzmann method.}, journal = {Computer methods and programs in biomedicine}, volume = {219}, number = {}, pages = {106757}, doi = {10.1016/j.cmpb.2022.106757}, pmid = {35338884}, issn = {1872-7565}, mesh = {Blood Flow Velocity ; Hemodynamics/physiology ; Humans ; *Intracranial Aneurysm/surgery ; Rheology ; Stents ; *Thrombosis/prevention & control ; }, abstract = {BACKGROUND AND OBJECTIVE: Treatment of intracranial aneurysms with flow-diverting stents prevents rupture by reducing blood flow and creating thrombosis within the aneurysm. This paper aims to assess the hemodynamic effect of placing stents with different struts (0, 3, 5, 7 struts) on intracranial aneurysms and to propose a simple prediction model of thrombosis zone without any further computational cost.

METHOD: Lattice Boltzmann method with different rheological models (Newtonian, Carreau-Yasuda, KL) of blood are used to study the hemodynamic effect of flow-diverting stents in the aneurysm. Pulsatile flow boundary conditions were applied in the inlet of the artery. The average Reynolds number was resulting Re = 111. The Lagrangian tracking of the particle was developed to assess the intra-aneurysmal blood stagnation. To predict the probable thrombose zone induced by flow-diverting stents, the shear rate threshold is utilized to determine the nodes of fluid to clot.

RESULTS: The results show that the flow patterns into the aneurysmal sac develop a vortex, decreasing after stent placement until disappearance for the stent with seven struts (porosity 71.4%). Velocity, shear rate, shear stress, trajectory, path length, and occlusion rate are compared before and after stent placement. These parameters decrease inversely with the porosity of the stent. The three models yield a closes result of the (velocity, shear rate, occlusion rate). Tracking the fluid-particle trajectory shows that the length of the particle paths decreases with the number of struts causing fluid to slow down and increase, consequently, the residence time into the sac.

CONCLUSION: The flow-diverting stents placement cause the reduction of dynamic flow within aneurysm. The reduction effect is almost the same below five struts (80% of porosity). The results show that, if our objective is restricted to estimating the hemodynamic effect, measured by (velocity, shear rate, occlusion rate), the differences between rheological behavior models are, practically, not significant, and the models can be used indifferently.}, } @article {pmid35334666, year = {2022}, author = {Nuwairan, MA and Souayeh, B}, title = {Simulation of Gold Nanoparticle Transport during MHD Electroosmotic Flow in a Peristaltic Micro-Channel for Biomedical Treatment.}, journal = {Micromachines}, volume = {13}, number = {3}, pages = {}, pmid = {35334666}, issn = {2072-666X}, support = {Grant No.207021//Deanship of Scientific Research at King Faisal University/ ; }, abstract = {The study of gold nanoparticles (AuNPs) in the blood flow has emerged as an area of interest for numerous researchers, due to its many biomedical applications, such as cancer radiotherapy, DNA and antigens, drug and gene delivery, in vitro evaluation, optical bioimaging, radio sensitization and laser phototherapy of cancer cells and tumors. Gold nanoparticles can be amalgamated in various shapes and sizes. Due to this reason, gold nanoparticles can be diffused efficiently, target the diseased cells and destroy them. The current work studies the effect of gold nanoparticles of different shapes on the electro-magneto-hydrodynamic (EMHD) peristaltic propulsion of blood in a micro-channel under various effects, such as activation energy, bioconvection, radiation and gyrotactic microorganisms. Four kinds of nanoparticle shapes, namely bricks, cylinders and platelets, are considered. The governing equations are simplified under the approximations of low Reynolds number (LRN), long wavelength (LWL) and Debye-Hückel linearization (DHL). The numerical solutions for the non-dimensional equations are solved using the computational software MATLAB with the help of the bvp4c function. The influences of different physical parameters on the flow and thermal characteristics are computed through pictorial interpretations.}, } @article {pmid35329572, year = {2022}, author = {Sawka, A}, title = {Chemical Vapour Deposition of Scandia-Stabilised Zirconia Layers on Tubular Substrates at Low Temperatures.}, journal = {Materials (Basel, Switzerland)}, volume = {15}, number = {6}, pages = {}, pmid = {35329572}, issn = {1996-1944}, support = {16.16.160.557//Subvention of the Polish State Ministry of Education and Science for AGH University of Science and Technology, Faculty of Materials Science and Ceramics/ ; }, abstract = {The paper presents results of investigation on synthesis of non-porous ZrO2-Sc2O2 layers on tubular substrates by MOCVD (metalorganic chemical vapor deposition) method using Sc(tmhd)3 (Tris(2,2,6,6-tetramethyl-3,5-heptanedionato)scandium(III), 99%) and Zr(tmhd)4 (Tetrakis(2,2,6,6-tetramethyl-3,5-heptanedionato)zirconium)(IV), 99.9+%) as basic reactants. The molar content of Sc(tmhd)3 in the gas mixture was as follows: 14, 28%. The synthesis temperature was in the range of 600-700 °C. The value of extended Grx/Rex2 expression (Gr-Grashof number, Re-Reynolds number and x-the distance from the gas inflow point) was less than 0.01. The layers were deposited under reduced pressure or close to atmospheric pressure. The layers obtained were tested using scanning electron microscope (SEM) with an energy dispersive X-ray spectroscope (EDS) microanalyzer, X-ray diffractometer and UV-Vis spectrophotometer. The layers deposited were non-porous, amorphous or nanocrystalline with controlled chemical composition. The layers synthesized at 700 °C were nanocrystalline. ZrO2-Sc2O3 layers with 14 mol.% Sc2O3 content had a rhombohedral structure.}, } @article {pmid35327926, year = {2022}, author = {Lin, W and Shi, R and Lin, J}, title = {Heat Transfer and Pressure Drop of Nanofluid with Rod-like Particles in Turbulent Flows through a Curved Pipe.}, journal = {Entropy (Basel, Switzerland)}, volume = {24}, number = {3}, pages = {}, pmid = {35327926}, issn = {1099-4300}, support = {12132015//National Natural Science Foundation of China/ ; }, abstract = {Pressure drop, heat transfer, and energy performance of ZnO/water nanofluid with rodlike particles flowing through a curved pipe are studied in the range of Reynolds number 5000 ≤ Re ≤ 30,000, particle volume concentration 0.1% ≤ Φ ≤ 5%, Schmidt number 104 ≤ Sc ≤ 3 × 105, particle aspect ratio 2 ≤ λ ≤ 14, and Dean number 5 × 103 ≤ De ≤ 1.5 × 104. The momentum and energy equations of nanofluid, together with the equation of particle number density for particles, are solved numerically. Some results are validated by comparing with the experimental results. The effect of Re, Φ, Sc, λ, and De on the friction factor f and Nusselt number Nu is analyzed. The results showed that the values of f are increased with increases in Φ, Sc, and De, and with decreases in Re and λ. The heat transfer performance is enhanced with increases in Re, Φ, λ, and De, and with decreases in Sc. The ratio of energy PEC for nanofluid to base fluid is increased with increases in Re, Φ, λ, and De, and with decreases in Sc. Finally, the formula of ratio of energy PEC for nanofluid to base fluid as a function of Re, Φ, Sc, λ, and De is derived based on the numerical data.}, } @article {pmid35327850, year = {2022}, author = {Dou, HS}, title = {No Existence and Smoothness of Solution of the Navier-Stokes Equation.}, journal = {Entropy (Basel, Switzerland)}, volume = {24}, number = {3}, pages = {}, doi = {10.3390/e24030339}, pmid = {35327850}, issn = {1099-4300}, abstract = {The Navier-Stokes equation can be written in a form of Poisson equation. For laminar flow in a channel (plane Poiseuille flow), the Navier-Stokes equation has a non-zero source term (∇2u(x, y, z) = Fx (x, y, z, t) and a non-zero solution within the domain. For transitional flow, the velocity profile is distorted, and an inflection point or kink appears on the velocity profile, at a sufficiently high Reynolds number and large disturbance. In the vicinity of the inflection point or kink on the distorted velocity profile, we can always find a point where ∇2u(x, y, z) = 0. At this point, the Poisson equation is singular, due to the zero source term, and has no solution at this point due to singularity. It is concluded that there exists no smooth orphysically reasonable solutions of the Navier-Stokes equation for transitional flow and turbulence in the global domain due to singularity.}, } @article {pmid35299996, year = {2022}, author = {Marchello, R and Morandotti, M and Shum, H and Zoppello, M}, title = {The N -Link Swimmer in Three Dimensions: Controllability and Optimality Results.}, journal = {Acta applicandae mathematicae}, volume = {178}, number = {1}, pages = {6}, pmid = {35299996}, issn = {0167-8019}, abstract = {The controllability of a fully three-dimensional N -link swimmer is studied. After deriving the equations of motion in a low Reynolds number fluid by means of Resistive Force Theory, the controllability of the minimal 2-link swimmer is tackled using techniques from Geometric Control Theory. The shape of the 2-link swimmer is described by two angle parameters. It is shown that the associated vector fields that govern the dynamics generate, via taking their Lie brackets, all eight linearly independent directions in the combined configuration and shape space, leading to controllability; the swimmer can move from any starting configuration and shape to any target configuration and shape by operating on the two shape variables. The result is subsequently extended to the N -link swimmer. Finally, the minimal time optimal control problem and the minimization of the power expended are addressed and a qualitative description of the optimal strategies is provided.}, } @article {pmid35297830, year = {2022}, author = {Wang, Y and Zhao, W and Wang, B and Wang, Y}, title = {Prediction model of combustion characteristics of methane-air using hyperspectral imaging.}, journal = {Applied optics}, volume = {61}, number = {7}, pages = {D75-D84}, doi = {10.1364/AO.444118}, pmid = {35297830}, issn = {1539-4522}, abstract = {Hyperspectral imaging can obtain considerable flame information, which can improve the prediction accuracy of combustion characteristics. This paper studies the hyperspectral characteristics of methane flames and proposes several prediction models. The experimental results show that the radiation intensity and radiation types of free radicals are related to the equivalent ratio, and the radiation region of free radicals becomes larger with the increase of the Reynolds number. The polynomial regression prediction models include the linear model and quadratic model. It takes C2∗/CH∗ as input parameters, and results can be available immediately. The three-dimensional convolutional neural network (3D-CNN) prediction model takes all spectral and spatial information in the flame hyperspectral image as input parameters. By improving the structural parameters of the convolution network, the final prediction errors of the equivalent ratio and Reynolds number are 2.84% and 3.11%, respectively. The method of combining the 3D-CNN model with hyperspectral imaging significantly improves the prediction accuracy, and it can be used to predict other combustion characteristics such as pollutant emissions and combustion efficiency.}, } @article {pmid35291149, year = {2022}, author = {Ma, X and Gong, X and Tang, Z and Jiang, N}, title = {Control of leading-edge separation on bioinspired airfoil with fluttering coverts.}, journal = {Physical review. E}, volume = {105}, number = {2-2}, pages = {025107}, doi = {10.1103/PhysRevE.105.025107}, pmid = {35291149}, issn = {2470-0053}, abstract = {In this work, the aerodynamic role of the artificial covert feathers (i.e., coverts) on an airfoil is experimentally studied in a wind tunnel to investigate the flow control effect on the leading-edge separation. We apply flexible featherlike devices on a high-angle-of-attack airfoil. We use a hot-wire anemometer to measure the velocity profiles and turbulent fluctuations in the downstream wake flow. As a baseline of flow separation, a two-dimensional NACA 0018 airfoil model is set at the angle of attack of 15 ° at the chord-based Reynolds number of 1.0×10^{5}, causing strong leading-edge and trailing-edge shear layers and a low-speed wake flow area in between as large as 0.35 chord length. When deployed on the upper wing surface, the flexible coverts adaptively flutter under the influence of the local unsteady airflow. Hot-wire measurement results show that the leading-edge coverts effectively suppress the flow separation and reduce the size of the wake flow area. The change of power spectral density shows that the predominant peaks as the fundamental and harmonic frequencies are both attenuated due to the suppression of unsteady motions of the shear layers. On the other hand, the fluttering coverts at the trailing edge modify the trailing-edge shear layer by redistributing the turbulent kinetic energy to the high-frequency components. By simultaneous double-point measurement, we find that the leading-edge and trailing-edge shear layers are drawn closer to each other, and the two shear layers show an increased peak in the coherence spectrum. Further multiscale wavelet analysis shows that the perturbations at the 60% chord length increase the large-scale amplitude modulation of small-scale turbulence and therefore they stabilize the leading-edge and trailing-edge shear layers. Meanwhile, the flow intermittency outside of the wake flow area is attenuated as well. The effective flow control effects in the present work are in good agreement with the previous direct observations of bird flight in literature that the coverts on the upper wing surface play an important role in flow separation control during high-angle-of-attack flight. These findings advance the understanding of aerodynamic contribution of the covers on bird wings and reveal the engineering potential of bioinspired coverts for flow separation control of aircrafts and unmanned air vehicles.}, } @article {pmid35270649, year = {2022}, author = {Ovando-Chacon, GE and Rodríguez-León, A and Ovando-Chacon, SL and Hernández-Ordoñez, M and Díaz-González, M and Pozos-Texon, FJ}, title = {Computational Study of Thermal Comfort and Reduction of CO2 Levels inside a Classroom.}, journal = {International journal of environmental research and public health}, volume = {19}, number = {5}, pages = {}, pmid = {35270649}, issn = {1660-4601}, mesh = {*Air Pollution, Indoor/analysis/prevention & control ; *COVID-19/epidemiology ; Carbon Dioxide/analysis ; Humans ; Pandemics ; SARS-CoV-2 ; }, abstract = {Due to the current COVID-19 pandemic, guaranteeing thermal comfort and low CO2 levels in classrooms through efficient ventilation has become vitally important. This study presents three-dimensional simulations based on computational fluid dynamics of airflow inside an air-conditioned classroom located in Veracruz, Mexico. The analysis included various positions of an air extractor, Reynolds numbers up to 3.5 × 104, four different concentrations of pollutant sources, and three different times of the day. The simulations produced velocity, air temperature, and CO2 concentrations fields, and we calculated average air temperatures, average CO2 concentrations, and overall ventilation effectiveness. Our results revealed an optimal extractor position and Reynolds number conducive to thermal comfort and low CO2 levels due to an adequate ventilation configuration. At high pollutant concentrations, it is necessary to reduce the number of students in the classroom to achieve safe CO2 levels.}, } @article {pmid35264611, year = {2022}, author = {Memon, AA and Memon, MA and Bhatti, K and Khan, I and Alshammari, N and Al-Johani, AS and Hamadneh, NN and Andualem, M}, title = {Thermal decomposition of propylene oxide with different activation energy and Reynolds number in a multicomponent tubular reactor containing a cooling jacket.}, journal = {Scientific reports}, volume = {12}, number = {1}, pages = {4169}, pmid = {35264611}, issn = {2045-2322}, abstract = {In this article, we are focusing on heat and mass transfer through a Multicomponent tubular reactor containing a cooling jacket by thermal decomposition of propylene oxide in water. The chemical reaction is an irreversible, 1st order reaction and an exothermic reaction that yields propylene glycol with enthalpy = -84,666 J/mol. The constant rate of the reaction is followed by the Arrhenius equation in which the activation energy is taken on a trial basis in the range from 75,000 to 80,000 J/mol with a fixed frequency factor. For the fluid to flow, the Reynolds number is kept in the range from 100 to 1000. The three partial differential equations of mass, momentum, and energy are coupled to study heat and mass transfer in a tubular reactor by using the chemistry interface in COMSOL Multiphysics 5.4. The initial concentration of propylene oxide is tested in the range from 2 to 3% and the thermal conductivity of the mixture is tested in the range 0.599-0.799. It was found that the amount deactivated of the compound decreases with an increase in Reynolds number. Propylene oxide is decomposed at about 99.8% at Re = 100 at lower activation energy and gives the total maximum enthalpy change in the tubular reactor. Observing the relationship between Sherwood numbers to Nusselt numbers, it was deducted that the convective heat transfer is opposite to convective mass transfer for high Reynolds numbers.}, } @article {pmid35236870, year = {2022}, author = {Khan, Z and Ul Haq, S and Ali, F and Andualem, M}, title = {Free convection flow of second grade dusty fluid between two parallel plates using Fick's and Fourier's laws: a fractional model.}, journal = {Scientific reports}, volume = {12}, number = {1}, pages = {3448}, pmid = {35236870}, issn = {2045-2322}, abstract = {The paper aims to investigate the channel flow of second grade visco-elastic fluid generated due to an oscillating wall. The effect of heat and mass transfer has been taken into account. The phenomenon has been modelled in terms of PDEs. The constitutive equations are fractionalized by using the definition of the Caputo fractional operator with Fick's and Fourier's Laws. The system of fractional PDEs is non-dimensionalized by using appropriate dimensionless variables. The closed-form solutions of thermal and concentration boundary layers are obtained by using the Laplace and finite Fourier-Sine transforms, while the momentum equation is solved by a numerical approach by Zakian using [Formula: see text]. Furthermore, the parametric influence of various embedded physical parameters on momentum, temperature, and concentration distributions is depicted through various graphs. It is observed that the fractional approach is more convenient and realistic as compared to the classical approach. It is worth noting that the increasing values of [Formula: see text], [Formula: see text] and [Formula: see text] retard the boundary layer profile. For instance, this behaviour of [Formula: see text] is significant where boundary control is necessary. That is, in the case of resonance, the physical solution may be obtained by adding the effect of MHD. The Reynolds number is useful in characterising the transport properties of a fluid or a particle travelling through a fluid. The Reynolds number is one of the main controlling parameters in all viscous flow. It determines whether the fluid flow is laminar or turbulent. The evolution of the rate of heat, mass transfer, and skin friction on the left plate with various physical parameters are presented in tables. These quantities are of high interest for engineers. Keeping in mind the effect of various parameters on these engineering quantities, they make their feasibility reports.}, } @article {pmid35233704, year = {2022}, author = {Cai, C and Wen, C and Guan, L and Huang, Y and Jiang, Q}, title = {Influence of sodium hypochlorite concentration on cavitation effect and fluid dynamics induced by photon-induced photoacoustic streaming (PIPS): A visualization study.}, journal = {Lasers in medical science}, volume = {}, number = {}, pages = {}, pmid = {35233704}, issn = {1435-604X}, support = {[2017]-210//Guangzhou Medical University/ ; [2017-160]//Guangzhou Medical University/ ; }, abstract = {PURPOSE: The aim of the present study was to visualize and compare the cavitation effect and fluid dynamics induced by photon-induced photoacoustic streaming (PIPS) using sodium hypochlorite (NaOCl) with different concentrations as irrigant.

METHODS: Forty artificial root canals were prepared using MTWO Niti file up to size #25/.06. The canals were randomly divided into four groups (n = 10/group). High-speed camera was used to visualize and compare the cavitation effect induced by PIPS in the artificial root canals containing saline or NaOCl. Fluid velocity and Reynolds number of saline, 1%-, 2.5%- and 5.25% NaOCl irrigants induced by PIPS in the apical region were calculated using TEMA 2D software while the fluid motions were recorded.

RESULTS: Visualization profile revealed that NaOCl presented a stronger cavitation effect and fluid dynamics than saline during PIPS activation. In the apical region, 1% NaOCl group presented the highest average velocity of 3.868 m/s, followed by 2.5% NaOCl group (3.685 m/s), 5.25% NaOCl group (2.353 m/s) and saline group (1.268 m/s), corresponding to Reynolds number of 1653.173, 1572.196, 995.503 and 477.692. Statistically higher fluid velocity was calculated in 1% and 2.5% NaOCl groups compared to saline group, respectively (p < 0.05).

CONCLUSIONS: The application of NaOCl and its concentration significantly influence the cavitation effect and fluid dynamics during PIPS activation. 1% and 2.5% NaOCl groups presented a more violent fluid motion in the apical region when activated by PIPS.}, } @article {pmid35232981, year = {2022}, author = {Abd-Alla, AM and Thabet, EN and Bayones, FS}, title = {Numerical solution for MHD peristaltic transport in an inclined nanofluid symmetric channel with porous medium.}, journal = {Scientific reports}, volume = {12}, number = {1}, pages = {3348}, pmid = {35232981}, issn = {2045-2322}, abstract = {The significance of the study is to determine of transferred heat and mass impact on the magneto-hydrodynamic peristalsis of Jeffery nanofluid through porous media with inclined symmetric channels whose walls are induced by peristaltic motion within porous media. The aim of this investagtion is to study the influence of various types of parameters such as Brownian motion, thermophoresis, buoyancy forces, and magnetic fields are studies on concentration, temperature, and axial velocity. The numerical solution has been achieved according to the long-wavelength and low Reynolds number approximation utilizing the MATLAB bvp4c function. The resultant dimensions of nonlinear governing equations were approached numerically through the Runge-Kutta- Fehlberg integration scheme, a MATLAB program. The influence of different factors such as the ratio of relaxation to retardation times, nanoparticle Grashof number, and magnetic field was discussed on concentration, temperature, and velocity profiles. tables and graphs were used to demonstrate the numerically computed numerical results. Plotting graphs were utilized for evaluating the pertinent parameters impacts on the aforementioned quantities based on computational results. According to the findings, the effect of the parameters are significant.}, } @article {pmid35214965, year = {2022}, author = {Khan, NA and Sulaiman, M and Tavera Romero, CA and Alshammari, FS}, title = {Analysis of Nanofluid Particles in a Duct with Thermal Radiation by Using an Efficient Metaheuristic-Driven Approach.}, journal = {Nanomaterials (Basel, Switzerland)}, volume = {12}, number = {4}, pages = {}, pmid = {35214965}, issn = {2079-4991}, abstract = {This study investigated the steady two-phase flow of a nanofluid in a permeable duct with thermal radiation, a magnetic field, and external forces. The basic continuity and momentum equations were considered along with the Buongiorno model to formulate the governing mathematical model of the problem. Furthermore, the intelligent computational strength of artificial neural networks (ANNs) was utilized to construct the approximate solution for the problem. The unsupervised objective functions of the governing equations in terms of mean square error were optimized by hybridizing the global search ability of an arithmetic optimization algorithm (AOA) with the local search capability of an interior point algorithm (IPA). The proposed ANN-AOA-IPA technique was implemented to study the effect of variations in the thermophoretic parameter (Nt), Hartmann number (Ha), Brownian (Nb) and radiation (Rd) motion parameters, Eckert number (Ec), Reynolds number (Re) and Schmidt number (Sc) on the velocity profile, thermal profile, Nusselt number and skin friction coefficient of the nanofluid. The results obtained by the designed metaheuristic algorithm were compared with the numerical solutions obtained by the Runge-Kutta method of order 4 (RK-4) and machine learning algorithms based on a nonlinear autoregressive network with exogenous inputs (NARX) and backpropagated Levenberg-Marquardt algorithm. The mean percentage errors in approximate solutions obtained by ANN-AOA-IPA are around 10-6 to 10-7. The graphical analysis illustrates that the velocity, temperature, and concentration profiles of the nanofluid increase with an increase in the suction parameter, Eckert number and Schmidt number, respectively. Solutions and the results of performance indicators such as mean absolute deviation, Theil's inequality coefficient and error in Nash-Sutcliffe efficiency further validate the proposed algorithm's utility and efficiency.}, } @article {pmid35214944, year = {2022}, author = {Apmann, K and Fulmer, R and Scherer, B and Good, S and Wohld, J and Vafaei, S}, title = {Nanofluid Heat Transfer: Enhancement of the Heat Transfer Coefficient inside Microchannels.}, journal = {Nanomaterials (Basel, Switzerland)}, volume = {12}, number = {4}, pages = {}, pmid = {35214944}, issn = {2079-4991}, abstract = {The purpose of this paper is to investigate the effects of a connector between two microchannels, for the first time. A brief literature review is provided to offer a better understanding on the impacts of concentration and the characteristics of nanoparticles on thermal conductivity, viscosity, and, consequently, the heat transfer coefficient inside the microchannels. The given literature review aims to help engineer nanofluids to enhance the heat transfer coefficient inside the microchannels. In this research, Fe3O4 nanoparticles were introduced into the base liquid to enhance the heat transfer coefficient inside the microchannels and to provide a better understanding of the impact of the connector between two microchannels. It was observed that the connector has a significant impact on enhancing the heat transfer coefficient inside the second microchannel, by increasing the level of randomness of molecules and particles prior to entering the second channel. The connector would act to refresh the memory of the fluid before entering the second channel, and as a result, the heat transfer coefficient in the second channel would start at a maximum value. Therefore, the overall heat transfer coefficient in both microchannels would increase for given conditions. The impacts of the Reynolds number and introducing nanoparticles in the base liquid on effects induced by the connector were investigated, suggesting that both factors play a significant role on the connector's impact on the heat transfer coefficient.}, } @article {pmid35209192, year = {2022}, author = {Kim, GB and Park, KH and Kim, SJ}, title = {Hemodynamics and Wall Shear Stress of Blood Vessels in Aortic Coarctation with Computational Fluid Dynamics Simulation.}, journal = {Molecules (Basel, Switzerland)}, volume = {27}, number = {4}, pages = {}, pmid = {35209192}, issn = {1420-3049}, support = {2021R1A2C1091322//National Research Foundation of Korea/ ; }, mesh = {Algorithms ; Aorta/abnormalities/diagnostic imaging/physiopathology ; Aortic Coarctation/*diagnosis/*physiopathology ; Blood Flow Velocity ; *Hemodynamics ; Humans ; *Models, Cardiovascular ; *Stress, Mechanical ; }, abstract = {The purpose of this study was to identify the characteristics of blood flow in aortic coarctation based on stenotic shape structure, stenosis rate, and the distribution of the wall load delivered into the blood vessels and to predict the impact on aneurysm formation and rupture of blood vessels by using a computational fluid dynamics modeling method. It was applied on the blood flow in abdominal aortic blood vessels in which stenosis occurred by using the commercial finite element software ADINA on fluid-solid interactions. The results of modeling, with an increasing stenosis rate and Reynolds number, showed the pressure drop was increased and the velocity was greatly changed. When the stenosis rate was the same, the pressure drop and the velocity change were larger in the stenosis with a symmetric structure than in the stenosis with an asymmetric one. Maximal changes in wall shear stress were observed in the area before stenosis and minimal changes were shown in stenosis areas. The minimal shear stress occurred at different locations depending on the stenosis shape models. With an increasing stenosis rate and Reynolds number, the maximal wall shear stress was increased and the minimal wall shear stress was decreased. Through such studies, it is thought that the characteristics of blood flow in the abdominal aorta where a stenosis is formed will be helpful in understanding the mechanism of growth of atherosclerosis and the occurrence and rupture of the abdominal aortic flow.}, } @article {pmid35208284, year = {2022}, author = {Antognoli, M and Tomasi Masoni, S and Mariotti, A and Mauri, R and Salvetti, MV and Brunazzi, E and Galletti, C}, title = {Mixing Improvement in a T-Shaped Micro-Junction through Small Rectangular Cavities.}, journal = {Micromachines}, volume = {13}, number = {2}, pages = {}, pmid = {35208284}, issn = {2072-666X}, abstract = {The T-shaped micro-junction is among the most used geometry in microfluidic applications, and many design modifications of the channel walls have been proposed to enhance mixing. In this work, we investigate through numerical simulations the introduction of one pair of small rectangular cavities in the lateral walls of the mixing channel just downstream of the confluence region. The aim is to preserve the simple geometry that has contributed to spread the practical use of the T-shaped micro-junction while suggesting a modification that should, in principle, work jointly with the vortical structures present in the mixing channel, further enhancing their efficiency in mixing without significant additional pressure drops. The performance is analyzed in the different flow regimes occurring by increasing the Reynolds number. The cavities are effective in the two highly-mixed flow regimes, viz., the steady engulfment and the periodic asymmetric regimes. This presence does not interfere with the formation of the vortical structures that promote mixing by convection in these two regimes, but it further enhances the mixing of the inlet streams in the near-wall region of the mixing channel without any additional cost, leading to better performance than the classical configuration.}, } @article {pmid35207114, year = {2022}, author = {Nichka, V and Mareev, S and Pismenskaya, N and Nikonenko, V and Bazinet, L}, title = {Mathematical Modeling of the Effect of Pulsed Electric Field Mode and Solution Flow Rate on Protein Fouling during Bipolar Membrane Electroacidificaiton of Caseinate Solution.}, journal = {Membranes}, volume = {12}, number = {2}, pages = {}, pmid = {35207114}, issn = {2077-0375}, support = {21-19-00087//Russian Science Foundation/ ; 210829409//Natural Sciences and Engineering Research Council/ ; }, abstract = {A one-dimensional non-stationary model was developed for a better understanding of the protein fouling formation mechanism during electroacidification of caseinate solution using electrodialysis with bipolar membranes (EDBM) in pulsed electric field (PEF) mode. Four different PEF modes were investigated with pulse-pause durations of 10-10 s, 10-20 s, 10-33 s, 10-50 s. For each current mode 3 different flow rates were considered, corresponding to Reynolds numbers, Re, equal to 187, 374 and 560. The processes are considered in the diffusion boundary layer between the surface of the cation-exchange layer of bipolar membrane and bulk solution of the desalination compartment. The Nernst-Planck and material balance equation systems describe the ion transport. The electroneutrality condition and equilibrium chemical reactions are taken into account. The calculation results using the developed model are in qualitative agreement with the experimental data obtained during the previous experimental part of the study. It is confirmed that both the electrical PEF mode and the flow rate have a significant effect on the thickness (and mass) of the protein fouling during EDBM. Moreover, the choice of the electric current mode has the main impact on the fouling formation rate; an increase in the PEF pause duration leads to a decrease in the amount of fouling. It was shown that an increase in the PEF pause duration from 10 s to 50 s, in combination with an increase in Reynolds number (the flow rate) from 187 to 560, makes it possible to reduce synergistically the mass of protein deposits from 6 to 1.3 mg/cm2, which corresponds to a 78% decrease.}, } @article {pmid35205589, year = {2022}, author = {Yang, X and Yang, L}, title = {Numerical Study of Entropy Generation in Fully Developed Turbulent Circular Tube Flow Using an Elliptic Blending Turbulence Model.}, journal = {Entropy (Basel, Switzerland)}, volume = {24}, number = {2}, pages = {}, doi = {10.3390/e24020295}, pmid = {35205589}, issn = {1099-4300}, abstract = {As computational fluid dynamics (CFD) advances, entropy generation minimization based on CFD becomes attractive for optimizing complex heat-transfer systems. This optimization depends on the accuracy of CFD results, such that accurate turbulence models, such as elliptic relaxation or elliptic blending turbulence models, become important. The performance of a previously developed elliptic blending turbulence model (the SST k-ω-φ-α model) to predict the rate of entropy generation in the fully developed turbulent circular tube flow with constant heat flux was studied to provide some guidelines for using this class of turbulence model to calculate entropy generation in complex systems. The flow and temperature fields were simulated by using a CFD package, and then the rate of entropy generation was calculated in post-processing. The analytical correlations and results of two popular turbulence models (the realizable k-ε and the shear stress transport (SST) k-ω models) were used as references to demonstrate the accuracy of the SST k-ω-φ-α model. The findings indicate that the turbulent Prandtl number (Prt) influences the entropy generation rate due to heat-transfer irreversibility. Prt = 0.85 produces the best results for the SST k-ω-φ-α model. For the realizable k-ε and SST k-ω models, Prt = 0.85 and Prt = 0.92 produce the best results, respectively. For the realizable k-ε and the SST k-ω models, the two methods used to predict the rate of entropy generation due to friction irreversibility produce the same results. However, for the SST k-ω-φ-α model, the rates of entropy generation due to friction irreversibility predicted by the two methods are different. The difference at a Reynolds number of 100,000 is about 14%. The method that incorporates the effective turbulent viscosity should be used to predict the rate of entropy generation due to friction irreversibility for the SST k-ω-φ-α model. Furthermore, when the temperature in the flow field changes dramatically, the temperature-dependent fluid properties must be considered.}, } @article {pmid35196405, year = {2022}, author = {Xia, N and Jin, B and Jin, D and Yang, Z and Pan, C and Wang, Q and Ji, F and Iacovacci, V and Majidi, C and Ding, Y and Zhang, L}, title = {Decoupling and Reprogramming the Wiggling Motion of Midge Larvae Using a Soft Robotic Platform.}, journal = {Advanced materials (Deerfield Beach, Fla.)}, volume = {34}, number = {17}, pages = {e2109126}, doi = {10.1002/adma.202109126}, pmid = {35196405}, issn = {1521-4095}, support = {JLFS/E-402/18//Hong Kong Research Grants Council/ ; MRP/036/18X//ITF/ ; //HKSAR Innovation and Technology Commission/ ; CAS20403//Croucher Foundation Grant/ ; U1930402//National Science Foundation of China/ ; }, mesh = {Animals ; Biomimetics ; Larva ; Locomotion ; *Robotics ; Swimming ; }, abstract = {The efficient motility of invertebrates helps them survive under evolutionary pressures. Reconstructing the locomotion of invertebrates and decoupling the influence of individual basic motion are crucial for understanding their underlying mechanisms, which, however, generally remain a challenge due to the complexity of locomotion gaits. Herein, a magnetic soft robot to reproduce midge larva's key natural swimming gaits is developed, and the coupling effect between body curling and rotation on motility is investigated. Through the authors' systematically decoupling studies using programmed magnetic field inputs, the soft robot (named LarvaBot) experiences various coupled gaits, including biomimetic side-to-side flexures, and unveils that the optimal rotation amplitude and the synchronization of curling and rotation greatly enhance its motility. The LarvaBot achieves fast locomotion and upstream capability at the moderate Reynolds number regime. The soft robotics-based platform provides new insight to decouple complex biological locomotion, and design programmed swimming gaits for the fast locomotion of soft-bodied swimmers.}, } @article {pmid35193246, year = {2022}, author = {Czelusniak, LE and Mapelli, VP and Wagner, AJ and Cabezas-Gómez, L}, title = {Shaping the equation of state to improve numerical accuracy and stability of the pseudopotential lattice Boltzmann method.}, journal = {Physical review. E}, volume = {105}, number = {1-2}, pages = {015303}, doi = {10.1103/PhysRevE.105.015303}, pmid = {35193246}, issn = {2470-0053}, abstract = {It has recently been shown that altering the shape of the metastable and unstable branches of an equation of state (EOS) can substantially improve the numerical accuracy of liquid and vapor densities in the pseudopotential lattice Boltzmann method [Peng et al., Phys. Rev. E 101, 063309 (2020)2470-004510.1103/PhysRevE.101.063309]. We found that this approach reduces stability of the method in nonequilibrium conditions and is unstable for bubbles at low reduced temperatures. Here we present an improved method for altering the shape of the metastable and unstable branches of the EOS which remains stable for both equilibrium and nonequilibrium situations and has no issues with bubbles. We also performed a detailed study of the stability of the methods for a droplet impact on a liquid film for reduced temperatures down to 0.35 with Reynolds number of 300. Our approach remained stable for a density ratio of up to 3.38×10^{4} .}, } @article {pmid35193206, year = {2022}, author = {Richter, SK and Menzel, AM}, title = {Mediated interactions between rigid inclusions in two-dimensional elastic or fluid films.}, journal = {Physical review. E}, volume = {105}, number = {1-1}, pages = {014609}, doi = {10.1103/PhysRevE.105.014609}, pmid = {35193206}, issn = {2470-0053}, abstract = {Interactions between rigid inclusions in continuous three-dimensional linearly elastic solids and low-Reynolds-number viscous fluids have largely been quantified in the past. Prime example systems are given by functionalized elastic composite materials or fluid colloidal suspensions. Here, we address the significantly less frequently studied situation of rigid inclusions in two-dimensional elastic or low-Reynolds-number fluid films. We concentrate on the situation in which disklike inclusions remain well separated from each other and do not get into contact. Specifically, we demonstrate and explain that the logarithmic divergence of the associated Green's function is removed in the absence of net external forces on the inclusions, in line with physical intuition. For instance, this situation applies when only pairwise mutual interactions between the inclusions prevail. Our results will support, for example, investigations on membranes functionalized by appropriate inclusions, both of technical or biological origin, or the dynamics of active microswimmers in appropriately prepared thin films.}, } @article {pmid35190663, year = {2022}, author = {Hamzah, HK and Ali, FH and Hatami, M}, title = {MHD mixed convection and entropy generation of CNT-water nanofluid in a wavy lid-driven porous enclosure at different boundary conditions.}, journal = {Scientific reports}, volume = {12}, number = {1}, pages = {2881}, pmid = {35190663}, issn = {2045-2322}, abstract = {In this study, Galerkin Finite Element Method or GFEM is used for the modeling of mixed convection with the entropy generation in wavy lid-driven porous enclosure filled by the CNT-water nanofluid under the magnetic field. Two different cases of boundary conditions for hot and cold walls are considered to study the fluid flow (streamlines) and heat transfer (local and average Nusselt numbers) as well as the entropy generation parameters. Richardson (Ri), Darcy (Da), Hartmann angle (γ), Amplitude (A), Number of peaks (N), Volume fraction (φ), Heat generation factor (λ), Hartmann number (Ha) and Reynolds number (Re) are studied parameters in this study which results indicated that at low Richardson numbers (< 1) increasing the inclined angle of magnetic field, decreases the Nu numbers, but at larger Richardson numbers (> 1) it improves the Nu numbers.}, } @article {pmid35184017, year = {2022}, author = {Bakos, V and Gyarmati, B and Csizmadia, P and Till, S and Vachoud, L and Nagy Göde, P and Tardy, GM and Szilágyi, A and Jobbágy, A and Wisniewski, C}, title = {Viscous and filamentous bulking in activated sludge: Rheological and hydrodynamic modelling based on experimental data.}, journal = {Water research}, volume = {214}, number = {}, pages = {118155}, doi = {10.1016/j.watres.2022.118155}, pmid = {35184017}, issn = {1879-2448}, abstract = {Although achieving good activated sludge settleability is a key requirement for meeting effluent quality criteria, wastewater treatment plants often face undesired floc structure changes. Filamentous bulking has widely been studied, however, viscous sludge formation much less investigated so far. Our main goal was to find relationship between sludge floc structure and related rheological properties, moreover, to estimate pressure loss in pipe networks through hydrodynamic modelling of the non-Newtonian flows in case of well settling (ideal-like), viscous and filamentous sludge. Severe viscous and filamentous kinds of bulking were generated separately in continuous-flow lab-scale systems initially seeded with the same reference (ideal-like) biomass and the entire evolution of viscous and filamentous bulking was monitored. The results suggested correlation between the rheological properties and the floc structure transformations, and showed the most appropriate fit for the Herschel-Bulkley model (vs. Power-law and Bingham). Validated computational fluid dynamics studies estimated the pipe pressure loss in a wide Reynolds number range for the initial well settling (reference) and the final viscous and filamentous sludge as well. A practical standard modelling protocol was developed for improving energy efficiency of sludge pumping in different floc structure scenarios.}, } @article {pmid35183949, year = {2022}, author = {Yu, Z and Yang, G and Zhang, W}, title = {A new model for the terminal settling velocity of microplastics.}, journal = {Marine pollution bulletin}, volume = {176}, number = {}, pages = {113449}, doi = {10.1016/j.marpolbul.2022.113449}, pmid = {35183949}, issn = {1879-3363}, mesh = {Environmental Monitoring ; *Microplastics ; Plastics ; *Water Pollutants, Chemical/analysis ; }, abstract = {Microplastic (MP) settling process is important for the transport of microplastic particles (MPs, <5 mm) in water bodies. However, for the control parameter of the drag coefficient (Cd), no generalized formula has been proposed for MPs of different shapes and materials. In this study, a total of 1343 MP settling data were collected from the literature. It was found that the drag law for perfect spheres cannot reasonably predict Cd for MPs with particle Reynolds number of 1-103. A new formula for Cd was developed by introducing the dimensionless particle diameter (d⁎) and two shape descriptors. The absolute error of the new formula is 15.2%, smaller than those (42.5-72.8%) of other existing formulas. Moreover, an explicit model was developed for MP settling velocity by correlating Cd, d⁎, and shape descriptors, with lower absolute error (8.8%) than those (15.4-77.2%) of existing models.}, } @article {pmid35160419, year = {2022}, author = {Faroughi, SA and Roriz, AI and Fernandes, C}, title = {A Meta-Model to Predict the Drag Coefficient of a Particle Translating in Viscoelastic Fluids: A Machine Learning Approach.}, journal = {Polymers}, volume = {14}, number = {3}, pages = {}, pmid = {35160419}, issn = {2073-4360}, support = {UID-B/05256/2020, UID-P/05256/2020, MIT-EXPL/TDI/0038/2019//FEDER funds through the COMPETE 2020 Programme and National Funds through FCT (Portuguese Foundation for Science and Technology)/ ; NORTE-07-0162-FEDER-000086//University of Minho cluster/ ; CPCA A2 6052 2020//Minho Advanced Computing Center/ ; HPC-EUROPA3 (INFRAIA-2016-1-730897)//Consorzio Interuniversitario dell'Italia Nord Est per il Calcolo Automatico (CINECA)/ ; icei-prace-2020-0009//PRACE - Partnership for Advanced Computing in Europe/ ; }, abstract = {This study presents a framework based on Machine Learning (ML) models to predict the drag coefficient of a spherical particle translating in viscoelastic fluids. For the purpose of training and testing the ML models, two datasets were generated using direct numerical simulations (DNSs) for the viscoelastic unbounded flow of Oldroyd-B (OB-set containing 12,120 data points) and Giesekus (GI-set containing 4950 data points) fluids past a spherical particle. The kinematic input features were selected to be Reynolds number, 0

METHODS: Computational Fluid Dynamics (CFD) approach is used to simulate the airflow in a neonate, an infant and an adult in sedentary breathing conditions. The healthy CT scans are segmented using MIMICS 21.0 (Materialise, Ann arbor, MI). The patient-specific 3D airway models are analyzed for low Reynolds number flow using ANSYS FLUENT 2020 R2. The applicability of the Grid Convergence Index (GCI) for polyhedral mesh adopted in this work is also verified.

RESULTS: This study shows that the inferior meatus of neonates accounted for only 15% of the total airflow. This was in contrast to the infants and adults who experienced 49 and 31% of airflow at the inferior meatus region. Superior meatus experienced 25% of total flow which is more than normal for the neonate. The highest velocity of 1.8, 2.6 and 3.7 m/s was observed at the nasal valve region for neonates, infants and adults, respectively. The anterior portion of the nasal cavity experienced maximum wall shear stress with average values of 0.48, 0.25 and 0.58 Pa for the neonates, infants and adults.

CONCLUSIONS: The neonates have an underdeveloped nasal cavity which significantly affects their airway distribution. The absence of inferior meatus in the neonates has limited the flow through the inferior regions and resulted in uneven flow distribution.}, } @article {pmid34846896, year = {2021}, author = {Kim, AR and Mitra, SK and Zhao, B}, title = {Reduced Pressure Drop in Viscoelastic Polydimethylsiloxane Wall Channels.}, journal = {Langmuir : the ACS journal of surfaces and colloids}, volume = {37}, number = {49}, pages = {14292-14301}, doi = {10.1021/acs.langmuir.1c02087}, pmid = {34846896}, issn = {1520-5827}, mesh = {Biological Transport ; *Dimethylpolysiloxanes ; *Lab-On-A-Chip Devices ; Viscosity ; }, abstract = {Polydimethylsiloxane (PDMS) is an important viscoelastic material that finds applications in a large number of engineering systems, particularly lab-on-chip microfluidic devices built with a flexible substrate. Channels made of PDMS, used for transporting analytes, are integral to these applications. The PDMS viscoelastic nature can induce additional hydrodynamic contributions at the soft wall/fluid interface compared to rigid walls. In this research, we investigated the pressure drop within PDMS channels bounded by rigid tubes (cellulose tubes). The bulging effect of the PDMS was limited by the rigid tubes under flowing fluids. The PDMS viscoelasticity was modulated by changing the ratio of the base to the cross-linker from 10:1 to 35:1. We observed that the pressure drop of the flowing fluids within the channel decreased with the increased loss tangent of the PDMS in the examined laminar regime [Reynolds number (Re) ∼ 23-58.6 for water and Re ∼ 0.69-8.69 for glycerol solution]. The elastic PDMS 10:1 wall channels followed the classical Hagen Poiseuille's equation, but the PDMS walls with lower cross-linker concentrations and thicker walls decreased pressure drops. The friction factor (f) for the PDMS channels with the two working fluids could be approximated as f = 47/Re. We provide a correlation between the pressure drop and PDMS viscoelasticity based on experimental findings. In the correlation, the loss tangent predominates; the larger the loss tangent, the smaller is the pressure drop. The research findings appear to be unexpected if only considering the energy dissipation of viscoelastic PDMS walls. We attributed the reduction in the pressure drop to a lubricating effect of the viscoelastic PDMS walls in the presence of the working fluids. Our results reveal the importance of the subtle diffusion of the residual oligomers and water from the bulk to the soft wall/fluid interface for the observed pressure drop in soft wall channels.}, } @article {pmid34846030, year = {2021}, author = {Chen, X and Zhan, Y and Fu, YI and Lin, J and Ji, Y and Zhao, C and Fang, Y and Wu, J}, title = {The effect of stenosis rate and Reynolds number on local flow characteristics and plaque formation around the atherosclerotic stenosis.}, journal = {Acta of bioengineering and biomechanics}, volume = {23}, number = {1}, pages = {135-147}, pmid = {34846030}, issn = {1509-409X}, mesh = {*Atherosclerosis ; Constriction, Pathologic ; Hemodynamics ; Humans ; *Models, Cardiovascular ; Stress, Mechanical ; }, abstract = {PURPOSE: Atherosclerosis causes plaque to build-up in arteries. Effect of the specific local hemodynamic environment around an atherosclerotic plaque on the thrombosis formation does not remain quite clear but is believed to be crucial. The aim of this study is to uncover the flow effects on plaques formation.

METHODS: To study the mechanically regulated plaque formation, the flow fields in artery blood vessels with different stenosis rates at various Reynolds numbers were simulated numerically with the two-dimensional axisymmetric models, and the hemodynamic characteristics around the plaque were scaled with stenosis rate and Reynolds number.

RESULTS: The results showed that increases of both Reynolds number and stenosis rate facilitated the occurrence of flow separation phenomenon, extended recirculation zone, and upregulated the maximum normalized wall shear stress near the plaque throat section while downregulated the minimal normalized wall shear stress at the front shoulder of plaque, as it should be; in the atherosclerotic plaque leeside of the recirculation zone, an obvious catch bond region of wall shear stress might exist especially under low Reynolds number with stenosis rate smaller than 30%. This catch bond region in the plaque leeside might be responsible for the LBF (low blood flow)-enhanced formation of the atherosclerotic plaque.

CONCLUSIONS: This work may provide a novel insight into understanding the biomechanical effects behind the formation and damage of atherosclerotic plaques and propose a new strategy for preventing atherosclerotic diseases.}, } @article {pmid34845537, year = {2021}, author = {Patel, K and Stark, H}, title = {Instability of a liquid sheet with viscosity contrast in inertial microfluidics.}, journal = {The European physical journal. E, Soft matter}, volume = {44}, number = {11}, pages = {144}, pmid = {34845537}, issn = {1292-895X}, abstract = {Flows at moderate Reynolds numbers in inertial microfluidics enable high throughput and inertial focusing of particles and cells with relevance in biomedical applications. In the present work, we consider a viscosity-stratified three-layer flow in the inertial regime. We investigate the interfacial instability of a liquid sheet surrounded by a density-matched but more viscous fluid in a channel flow. We use linear stability analysis based on the Orr-Sommerfeld equation and direct numerical simulations with the lattice Boltzmann method (LBM) to perform an extensive parameter study. Our aim is to contribute to a controlled droplet production in inertial microfluidics. In the first part, on the linear stability analysis we show that the growth rate of the fastest growing mode [Formula: see text] increases with the Reynolds number [Formula: see text] and that its wavelength [Formula: see text] is always smaller than the channel width w for sufficiently small interfacial tension [Formula: see text]. For thin sheets we find the scaling relation [Formula: see text], where m is viscosity ratio and [Formula: see text] the sheet thickness. In contrast, for thicker sheets [Formula: see text] decreases with increasing [Formula: see text] or m due to the nearby channel walls. Examining the eigenvalue spectra, we identify Yih modes at the interface. In the second part on the LBM simulations, the thin liquid sheet develops two distinct dynamic states: waves traveling along the interface and breakup into droplets with bullet shape. For smaller flow rates and larger sheet thicknesses, we also observe ligament formation and the sheet eventually evolves irregularly. Our work gives some indication how droplet formation can be controlled with a suitable parameter set [Formula: see text].}, } @article {pmid34845318, year = {2021}, author = {Pang, M and Zhang, T and Meng, Y and Ling, Z}, title = {Experimental study on the permeability of crushed coal medium based on the Ergun equation.}, journal = {Scientific reports}, volume = {11}, number = {1}, pages = {23030}, pmid = {34845318}, issn = {2045-2322}, support = {51774234//the National Natural Science Foundations of China/ ; }, abstract = {Accurate determination of the permeability of crushed coal medium is the basis for the study of their permeability characteristics. To investigate the permeability characteristics of this special porous medium composed of crushed coal particles, the permeability parameters of crushed coal specimens of different initial porosities were measured by designing a lateral-limit compression seepage test system. Parameters were determined separately for specimens of different initial porosities. (1) the Reynolds number distribution region characterising the seepage state was determined and obtained. Specimens with initial porosity distribution between 0.02 and 0.08, and seepage Reynolds number distribution in the low-permeability zone, under Darcy flow; (2) the intrinsic permeability of the crushed coal medium was obtained by using the Ergun equation. The complex inverse proportional relationship between the drag coefficient and Reynolds number was derived; (3) Through the determination of the permeability of the crushed coal medium, the mean value of βK value was obtained to be about 45.7, and the analysis of the permeability of porous medium can determine its critical permeability. The relationship between the Forchheimer number Fo and critical Reynolds number was measured. The results indicate that it conforms to a linear distribution. In-depth analysis of these two parameters can be used to explore the flow transition process between laminar, transition, and turbulent flow. This study provides insight into the permeability characteristics of the media in fractured coal bodies.}, } @article {pmid34840965, year = {2021}, author = {Krane, M}, title = {Vortex Formation Times in the Glottal Jet, Measured in a Scaled-Up Model.}, journal = {Fluids (Basel, Switzerland)}, volume = {6}, number = {11}, pages = {}, pmid = {34840965}, issn = {2311-5521}, support = {R01 DC005642/DC/NIDCD NIH HHS/United States ; }, abstract = {In this paper, the timing of vortex formation on the glottal jet is studied using previously published velocity measurements of flow through a scaled-up model of the human vocal folds. The relative timing of the pulsatile glottal jet and the instability vortices are acoustically important since they determine the harmonic and broadband content of the voice signal. Glottis exit jet velocity time series were extracted from time-resolved planar DPIV measurements. These measurements were acquired at four glottal flow speeds (u SS = 16.1-38 cm/s) and four glottis open times (T o = 5.67-23.7 s), providing a Reynolds number range Re = 4100-9700 and reduced vibration frequency f* = 0.01-0.06. Exit velocity waveforms showed temporal behavior on two time scales, one that correlates to the period of vibration and another characterized by short, sharp velocity peaks (which correlate to the passage of instability vortices through the glottis exit plane). The vortex formation time, estimated by computing the time difference between subsequent peaks, was shown to be not well-correlated from one vibration cycle to the next. The principal finding is that vortex formation time depends not only on cycle phase, but varies strongly with reduced frequency of vibration. In all cases, a strong high-frequency burst of vortex motion occurs near the end of the cycle, consistent with perceptual studies using synthesized speech.}, } @article {pmid34832781, year = {2021}, author = {Jbeili, M and Zhang, J}, title = {Effects of Microscopic Properties on Macroscopic Thermal Conductivity for Convective Heat Transfer in Porous Materials.}, journal = {Micromachines}, volume = {12}, number = {11}, pages = {}, pmid = {34832781}, issn = {2072-666X}, support = {Discovery Grant - Individual//Natural Sciences and Engineering Research Council/ ; }, abstract = {Porous materials are widely used in many heat transfer applications. Modeling porous materials at the microscopic level can accurately incorporate the detailed structure and substance parameters and thus provides valuable information for the complex heat transfer processes in such media. In this study, we use the generalized periodic boundary condition for pore-scale simulations of thermal flows in porous materials. A two-dimensional porous model consisting of circular solid domains is considered, and comprehensive simulations are performed to study the influences on macroscopic thermal conductivity from several microscopic system parameters, including the porosity, Reynolds number, and periodic unit aspect ratio and the thermal conductance at the solid-fluid interface. Our results show that, even at the same porosity and Reynolds number, the aspect ratio of the periodic unit and the interfacial thermal conductance can significantly affect the macroscopic thermal behaviors of porous materials. Qualitative analysis is also provided to relate the apparent thermal conductivity to the complex flow and temperature distributions in the microscopic porous structure. The method, findings and discussions presented in this paper could be useful for fundamental studies, material development, and engineering applications of porous thermal flow systems.}, } @article {pmid34828226, year = {2021}, author = {Li, W and Xie, Z and Xi, K and Xia, S and Ge, Y}, title = {Constructal Optimization of Rectangular Microchannel Heat Sink with Porous Medium for Entropy Generation Minimization.}, journal = {Entropy (Basel, Switzerland)}, volume = {23}, number = {11}, pages = {}, pmid = {34828226}, issn = {1099-4300}, support = {51979278//National Natural Science Foundation of China/ ; 51579244//National Natural Science Foundation of China/ ; }, abstract = {A model of rectangular microchannel heat sink (MCHS) with porous medium (PM) is developed. Aspect ratio of heat sink (HS) cell and length-width ratio of HS are optimized by numerical simulation method for entropy generation minimization (EGM) according to constructal theory. The effects of inlet Reynolds number (Re) of coolant, heat flux on bottom, porosity and volume proportion of PM on dimensionless entropy generation rate (DEGR) are analyzed. From the results, there are optimal aspect ratios to minimize DEGR. Given the initial condition, DEGR is 33.10% lower than its initial value after the aspect ratio is optimized. With the increase of Re, the optimal aspect ratio declines, and the minimum DEGR drops as well. DEGR gets larger and the optimal aspect ratio remains constant with the increasing of heat flux on bottom. For the different volume proportion of PM, the optimal aspect ratios are diverse, but the minimum DEGR almost stays unchanged. The twice minimized DEGR, which results from aspect ratio and length-width ratio optimized simultaneously, is 10.70% lower than the once minimized DEGR. For a rectangular bottom, a lower DEGR can be reached by choosing the proper direction of fluid flow.}, } @article {pmid34828211, year = {2021}, author = {Khan, MF and Sulaiman, M and Tavera Romero, CA and Alkhathlan, A}, title = {A Hybrid Metaheuristic Based on Neurocomputing for Analysis of Unipolar Electrohydrodynamic Pump Flow.}, journal = {Entropy (Basel, Switzerland)}, volume = {23}, number = {11}, pages = {}, pmid = {34828211}, issn = {1099-4300}, abstract = {A unipolar electrohydrodynamic (UP-EHD) pump flow is studied with known electric potential at the emitter and zero electric potential at the collector. The model is designed for electric potential, charge density, and electric field. The dimensionless parameters, namely the electrical source number (Es), the electrical Reynolds number (ReE), and electrical slip number (Esl), are considered with wide ranges of variation to analyze the UP-EHD pump flow. To interpret the pump flow of the UP-EHD model, a hybrid metaheuristic solver is designed, consisting of the recently developed technique sine-cosine algorithm (SCA) and sequential quadratic programming (SQP) under the influence of an artificial neural network. The method is abbreviated as ANN-SCA-SQP. The superiority of the technique is shown by comparing the solution with reference solutions. For a large data set, the technique is executed for one hundred independent experiments. The performance is evaluated through performance operators and convergence plots.}, } @article {pmid34828180, year = {2021}, author = {Jia, Y and Huang, J and Wang, J and Li, H}, title = {Heat Transfer and Fluid Flow Characteristics of Microchannel with Oval-Shaped Micro Pin Fins.}, journal = {Entropy (Basel, Switzerland)}, volume = {23}, number = {11}, pages = {}, pmid = {34828180}, issn = {1099-4300}, support = {5210060458//National Natural Science Foundation of China/ ; JJKH20210112KJ//The Scientific research project of Jilin Provincial Department of Education/ ; }, abstract = {A novel microchannel heat sink with oval-shaped micro pin fins (MOPF) is proposed and the characteristics of fluid flow and heat transfer are studied numerically for Reynolds number (Re) ranging from 157 to 668. In order to study the influence of geometry on flow and heat transfer characteristics, three non-dimensional variables are defined, such as the fin axial length ratio (α), width ratio (β), and height ratio (γ). The thermal enhancement factor (η) is adopted as an evaluation criterion to evaluate the best comprehensive thermal-hydraulic performance of MOPF. Results indicate that the oval-shaped pin fins in the microchannel can effectively prevent the rise of heat surface temperature along the flow direction, which improves the temperature distribution uniformity. In addition, results show that for the studied Reynolds number range and microchannel geometries in this paper, the thermal enhancement factor η increases firstly and then decreases with the increase of α and β. In addition, except for Re = 157, η decreases first and then increases with the increase of the fin height ratio γ. The thermal enhancement factor for MOPF with α = 4, β = 0.3, and γ = 0.5 achieves 1.56 at Re = 668. The results can provide a theoretical basis for the design of a microchannel heat exchanger.}, } @article {pmid34818642, year = {2021}, author = {Hernández Meza, JM and Vélez-Cordero, JR and Ramírez Saito, A and Aranda-Espinoza, S and Arauz-Lara, JL and Yáñez Soto, B}, title = {Particle/wall electroviscous effects at the micron scale: comparison between experiments, analytical and numerical models.}, journal = {Journal of physics. Condensed matter : an Institute of Physics journal}, volume = {34}, number = {9}, pages = {}, doi = {10.1088/1361-648X/ac3cef}, pmid = {34818642}, issn = {1361-648X}, abstract = {We report a experimental study of the motion of 1 μm single particles interacting with functionalized walls at low and moderate ionic strengths conditions. The 3D particle's trajectories were obtained by analyzing the diffracted particle images (point spread function). The studied particle/wall systems include negatively charged particles interacting with bare glass, glass covered with polyelectrolytes and glass covered with a lipid monolayer. In the low salt regime (pure water) we observed a retardation effect of the short-time diffusion coefficients when the particle interacts with a negatively charged wall; this effect is more severe in the perpendicular than in the lateral component. The decrease of the diffusion as a function of the particle-wall distancehwas similar regardless the origin of the negative charge at the wall. When surface charge was screened or salt was added to the medium (10 mM), the diffusivity curves recover the classical hydrodynamic behavior. Electroviscous theory based on the thin electrical double layer (EDL) approximation reproduces the experimental data except for smallh. On the other hand, 2D numerical solutions of the electrokinetic equations showed good qualitative agreement with experiments. The numerical model also showed that the hydrodynamic and Maxwellian part of the electroviscous total drag tend to zero ash→ 0 and how this is linked with the merging of both EDL's at close proximity.}, } @article {pmid34816334, year = {2021}, author = {Díaz, MV}, title = {On the long-time persistence of hydrodynamic memory.}, journal = {The European physical journal. E, Soft matter}, volume = {44}, number = {11}, pages = {141}, pmid = {34816334}, issn = {1292-895X}, abstract = {The Basset-Boussinesq-Oseen (BBO) equation correctly describes the nonuniform motion of a spherical particle at a low Reynolds number. It contains an integral term with a singular kernel which accounts for the diffusion of vorticity around the particle throughout its entire history. However, if there are any departures in either rigidity or shape from a solid sphere, besides the integral force with a singular kernel, the Basset history force, we should add a second history force with a non-singular kernel, related to the shape or composition of the particle. In this work, we introduce a fractional generalized Basset-Boussinesq-Oseen equation which includes both history terms as fractional derivatives. Using the Laplace transform, an integral representation of the solution is obtained. For a driven single particle, the solution shows that memory effects persist indefinitely under rather general driving conditions.}, } @article {pmid34805706, year = {2021}, author = {Yin, B and Yue, W and Sohan, ASMMF and Zhou, T and Qian, C and Wan, X}, title = {Micromixer with Fine-Tuned Mathematical Spiral Structures.}, journal = {ACS omega}, volume = {6}, number = {45}, pages = {30779-30789}, pmid = {34805706}, issn = {2470-1343}, abstract = {Micromixers with the microchannel structure can enable rapid and efficient mixing of multiple types of fluids on a microfluidic chip. Herein, we report the mixing performance of three passive micromixers based on the different mathematical spiral structures. We study the fluid flow characteristics of Archimedes spiral, Fermat spiral, and hyperbolic spiral structures with various channel widths and Reynolds number (Re) ranging from 0 to 10 via numerical simulation and visualization experiments. In addition, we analyze the mechanism of streamlines and Dean vortices at different cross sections during fluid flows. As the fluid flows in the Fermat spiral channel, the centrifugal force induces the Dean vortex to form a chaotic advection, enhancing the fluid mixing performance. By integrating the Fermat spiral channel into a microfluidic chip, we successfully detect acute myocardial infarction (AMI) marker with the double-antibody sandwich method and reduce the detection time to 10 min. This method has a low reagent consumption and a high reaction efficiency and demonstrates great potential in point-of-care testing (POCT).}, } @article {pmid34797128, year = {2021}, author = {Jaccod, A and Chibbaro, S}, title = {Constrained Reversible System for Navier-Stokes Turbulence.}, journal = {Physical review letters}, volume = {127}, number = {19}, pages = {194501}, doi = {10.1103/PhysRevLett.127.194501}, pmid = {34797128}, issn = {1079-7114}, abstract = {Following a Gallavotti's conjecture, stationary states of Navier-Stokes fluids are proposed to be described equivalently by alternative equations besides the Navier-Stokes equation itself. We discuss a model system symmetric under time reversal based on the Navier-Stokes equations constrained to keep the enstrophy constant. It is demonstrated through highly resolved numerical experiments that the reversible model evolves to a stationary state which reproduces quite accurately all statistical observables relevant for the physics of turbulence extracted by direct numerical simulations (DNS) at different Reynolds numbers. The possibility of using reversible models to mimic turbulence dynamics is of practical importance for the coarse-grained version of Navier-Stokes equations, as used in large-eddy simulations. Furthermore, the reversible model appears mathematically simpler, since enstrophy is bounded to be constant for every Reynolds number. Finally, the theoretical interest in the context of statistical mechanics is briefly discussed.}, } @article {pmid34781498, year = {2021}, author = {An, X and Dong, B and Wang, Y and Zhang, Y and Zhou, X and Li, W}, title = {Coupled lattice Boltzmann-large eddy simulation model for three-dimensional multiphase flows at large density ratio and high Reynolds number.}, journal = {Physical review. E}, volume = {104}, number = {4-2}, pages = {045305}, doi = {10.1103/PhysRevE.104.045305}, pmid = {34781498}, issn = {2470-0053}, abstract = {A coupled lattice Boltzmann-large eddy simulation model is developed for modeling three-dimensional multiphase flows at large density ratios and high Reynolds numbers. In the framework of the lattice Boltzmann method, the model is proposed based on the standard Smagorinsky subgrid-scale approach, and a reconstructed multiple-relaxation-time collision operator is adopted. The conservative Allen-Cahn equation and Navier-Stokes equations are solved through the lattice Boltzmann discretization scheme for the interface tracking and velocity field evolution, respectively. Relevant benchmark cases are carried out to validate the performance of this model in simulating multiphase flows at a large density ratio and a high Reynolds number, including a stationary droplet, the process of spinodal decomposition, the Rayleigh-Taylor instability, the phenomenon of a droplet splashing on a thin liquid film, and the liquid jet breakup process. The maximum values of density ratio and Re number are 1000 and 10 240, respectively. The capability and reliability of the proposed model have been demonstrated by the good agreement between simulation results and the analytical solutions or the previously available results.}, } @article {pmid34776531, year = {2021}, author = {Braun, S and Scheichl, S and Kuzdas, D}, title = {The triple-deck stage of marginal separation.}, journal = {Journal of engineering mathematics}, volume = {128}, number = {1}, pages = {16}, pmid = {34776531}, issn = {0022-0833}, abstract = {The method of matched asymptotic expansions is applied to the investigation of transitional separation bubbles. The problem-specific Reynolds number is assumed to be large and acts as the primary perturbation parameter. Four subsequent stages can be identified as playing key roles in the characterization of the incipient laminar-turbulent transition process: due to the action of an adverse pressure gradient, a classical laminar boundary layer is forced to separate marginally (I). Taking into account viscous-inviscid interaction then enables the description of localized, predominantly steady, reverse flow regions (II). However, certain conditions (e.g. imposed perturbations) may lead to a finite-time breakdown of the underlying reduced set of equations. The ensuing consideration of even shorter spatio-temporal scales results in the flow being governed by another triple-deck interaction. This model is capable of both resolving the finite-time singularity and reproducing the spike formation (III) that, as known from experimental observations and direct numerical simulations, sets in prior to vortex shedding at the rear of the bubble. Usually, the triple-deck stage again terminates in the form of a finite-time blow-up. The study of this event gives rise to a noninteracting Euler-Prandtl stage (IV) associated with unsteady separation, where the vortex wind-up and shedding process takes place. The focus of the present paper lies on the triple-deck stage III and is twofold: firstly, a comprehensive numerical investigation based on a Chebyshev collocation method is presented. Secondly, a composite asymptotic model for the regularization of the ill-posed Cauchy problem is developed.

SUPPLEMENTARY INFORMATION: The online version contains supplementary material available at 10.1007/s10665-021-10125-3.}, } @article {pmid34766181, year = {2022}, author = {Yu, P and Durgesh, V}, title = {Application of Dynamic Mode Decomposition to Study Temporal Flow Behavior in a Saccular Aneurysm.}, journal = {Journal of biomechanical engineering}, volume = {144}, number = {5}, pages = {}, doi = {10.1115/1.4052999}, pmid = {34766181}, issn = {1528-8951}, mesh = {Blood Flow Velocity ; Hemodynamics ; Humans ; *Intracranial Aneurysm ; Models, Cardiovascular ; Rheology ; }, abstract = {Aneurysms are abnormal expansion of weakened blood vessels which can cause mortality or long-term disability upon rupture. Several studies have shown that inflow conditions spatially and temporally influence aneurysm flow behavior. The objective of this investigation is to identify impact of inflow conditions on spatio-temporal flow behavior in an aneurysm using dynamic mode decomposition (DMD). For this purpose, low-frame rate velocity field measurements are performed in an idealized aneurysm model using particle image velocimetry (PIV). The inflow conditions are precisely controlled using a ViVitro SuperPump system where nondimensional fluid parameters such as peak Reynolds number (Rep) and Womersely number (α) are varied from 50-270 and 2-5, respectively. The results show the ability of DMD to identify the spatial flow structures and their frequency content. Furthermore, DMD captured the impact of inflow conditions, and change in mode shapes, amplitudes, frequency, and growth rate information is observed. The DMD low-order flow reconstruction also showed the complex interplay of flow features for each inflow scenario. Furthermore, the low-order reconstruction results provided a mathematical description of the flow behavior in the aneurysm which captured the vortex formation, evolution, and convection in detail. These results indicated that the vortical structure behavior varied with the change in α while its strength and presence of secondary structures are influenced by the change in Rep.}, } @article {pmid34756978, year = {2022}, author = {Hu, F and Zhang, S and Wang, X and Wang, C and Wu, J and Poncin, S and Xu, L and Xu, G and Hu, Y and Li, HZ}, title = {Quantitative hydrodynamic characterization of high solid anaerobic digestion: Correlation of "mixing-fluidity-energy" and scale-up effect.}, journal = {Bioresource technology}, volume = {344}, number = {Pt B}, pages = {126237}, doi = {10.1016/j.biortech.2021.126237}, pmid = {34756978}, issn = {1873-2976}, mesh = {Anaerobiosis ; *Bioreactors ; *Hydrodynamics ; Rheology ; }, abstract = {High solid anaerobic digestion (HSAD)'s complex rheological behavior exhibits short-circuiting and dead zone. Mixing optimization is potential to enhance HSAD hydrodynamics. Besides, scale-up effect is quite essential for HSAD's applications, but remains rarely studied yet. Effect of impeller with different width on the correlation of "mixing-fluidity-energy" at different rotating speeds was first investigated at pilot-scale in present work. Then, scale-up effect based on rotating speed and a generalized Reynolds number was revealed from the aspects of fluidity and energy consumption. Results show that impeller width of 100 mm (10 rpm), 200 mm and 300 mm (5 and 10 rpm) are preferred for hydrodynamics and energy economics. Furthermore, Re similarity has better referential significance for the scale-up. In this study, new insight is gained into the correlation of "mixing-fluidity-energy" within a pilot-scale digester. Scale-up effect based Re similarity could potentially offer guidance for HSAD's application in the practical engineering.}, } @article {pmid34746583, year = {2021}, author = {Lian, SJ and Hu, ZX and Lan, Z and Wen, RF and Ma, XH}, title = {Optimal Operation of an Oscillatory Flow Crystallizer: Coupling Disturbance and Stability.}, journal = {ACS omega}, volume = {6}, number = {43}, pages = {28912-28922}, pmid = {34746583}, issn = {2470-1343}, abstract = {In the process of industrial crystallization, it is always difficult to balance the secondary nucleation rate and metastable zone width (MSZW). Herein, we report an experimental and numerical study for the cooling crystallization of paracetamol in an oscillatory flow crystallizer (OFC), finding the optimal operating conditions for balancing the secondary nucleation rate and MSZW. The results show that the MSZW decreases with the increase of oscillation Reynolds number (Re o). Compared to the traditional stirring system, the OFC has an MSZW three times larger than that of the stirring system under a similar power density of consumption. With the numerical simulation, the OFC can produce a stable space environment and instantaneous strong disturbance, which is conducive to the crystallization process. Above all, a high Re o is favorable to produce a sufficient nucleation rate, which may inevitably constrict the MSZW to a certain degree. Then, the optimization strategy of the operating parameter (Re o) in the OFC is proposed.}, } @article {pmid34739321, year = {2021}, author = {Browne, CA and Datta, SS}, title = {Elastic turbulence generates anomalous flow resistance in porous media.}, journal = {Science advances}, volume = {7}, number = {45}, pages = {eabj2619}, pmid = {34739321}, issn = {2375-2548}, abstract = {Many energy, environmental, industrial, and microfluidic processes rely on the flow of polymer solutions through porous media. Unexpectedly, the macroscopic flow resistance often increases above a threshold flow rate in a porous medium, but not in bulk solution. The reason why has been a puzzle for over half a century. Here, by directly visualizing flow in a transparent 3D porous medium, we demonstrate that this anomalous increase is due to the onset of an elastic instability in which the flow exhibits strong spatiotemporal fluctuations reminiscent of inertial turbulence, despite the small Reynolds number. Our measurements enable us to quantitatively establish that the energy dissipated by pore-scale fluctuations generates the anomalous increase in the overall flow resistance. Because the macroscopic resistance is one of the most fundamental descriptors of fluid flow, our results both help deepen understanding of complex fluid flows and provide guidelines to inform a broad range of applications.}, } @article {pmid34739267, year = {2021}, author = {Bott, AFA and Chen, L and Boutoux, G and Caillaud, T and Duval, A and Koenig, M and Khiar, B and Lantuéjoul, I and Le-Deroff, L and Reville, B and Rosch, R and Ryu, D and Spindloe, C and Vauzour, B and Villette, B and Schekochihin, AA and Lamb, DQ and Tzeferacos, P and Gregori, G and Casner, A}, title = {Inefficient Magnetic-Field Amplification in Supersonic Laser-Plasma Turbulence.}, journal = {Physical review letters}, volume = {127}, number = {17}, pages = {175002}, doi = {10.1103/PhysRevLett.127.175002}, pmid = {34739267}, issn = {1079-7114}, abstract = {We report a laser-plasma experiment that was carried out at the LMJ-PETAL facility and realized the first magnetized, turbulent, supersonic (Ma_{turb} ≈2.5) plasma with a large magnetic Reynolds number (Rm≈45) in the laboratory. Initial seed magnetic fields were amplified, but only moderately so, and did not become dynamically significant. A notable absence of magnetic energy at scales smaller than the outer scale of the turbulent cascade was also observed. Our results support the notion that moderately supersonic, low-magnetic-Prandtl-number plasma turbulence is inefficient at amplifying magnetic fields compared to its subsonic, incompressible counterpart.}, } @article {pmid34737529, year = {2021}, author = {Behera, S and Bhardwaj, R and Agrawal, A}, title = {Effect of co-flow on fluid dynamics of a cough jet with implications in spread of COVID-19.}, journal = {Physics of fluids (Woodbury, N.Y. : 1994)}, volume = {33}, number = {10}, pages = {101701}, pmid = {34737529}, issn = {1070-6631}, abstract = {We discuss the temporal evolution of a cough jet of an infected subject in the context of the spread of COVID-19. Computations were carried out using large eddy simulation, and, in particular, the effect of the co-flow (5% and 10% of maximum cough velocity) on the evolution of the jet was quantified. The Reynolds number (Re) of the cough jet, based on the mouth opening diameter (D) and the average cough velocity, is 13 002. The time-varying inlet velocity profile of the cough jet is represented as a combination of gamma-probability-distribution functions. Simulations reveal the detailed structure of cough jet with and without a co-flow for the first time, to the best of our knowledge. The cough jet temporal evolution is similar to that of a continuous free-jet and follows the same routes of instability, as documented for a free-jet. The convection velocity of the cough jet decays with time and distance, following a power-law variation. The cough jet is observed to travel a distance of approximately 1.1 m in half a second. However, in the presence of 10% co-flow, the cough jet travels faster and covers the similar distance in just 0.33 s. Therefore, in the presence of a co-flow, the probability of transmission of COVID-19 by airborne droplets and droplet nuclei increases, since they can travel a larger distance. The cough jet without the co-flow corresponds to a larger volume content compared to that with the co-flow and spreads more within the same range of distance. These simulations are significant as they help to reveal the intricate structure of the cough jet and show that the presence of a co-flow can significantly augment the risk of infection of COVID-19.}, } @article {pmid34732570, year = {2021}, author = {Choueiri, GH and Lopez, JM and Varshney, A and Sankar, S and Hof, B}, title = {Experimental observation of the origin and structure of elastoinertial turbulence.}, journal = {Proceedings of the National Academy of Sciences of the United States of America}, volume = {118}, number = {45}, pages = {}, pmid = {34732570}, issn = {1091-6490}, abstract = {Turbulence generally arises in shear flows if velocities and hence, inertial forces are sufficiently large. In striking contrast, viscoelastic fluids can exhibit disordered motion even at vanishing inertia. Intermediate between these cases, a state of chaotic motion, "elastoinertial turbulence" (EIT), has been observed in a narrow Reynolds number interval. We here determine the origin of EIT in experiments and show that characteristic EIT structures can be detected across an unexpectedly wide range of parameters. Close to onset, a pattern of chevron-shaped streaks emerges in qualitative agreement with linear and weakly nonlinear theory. However, in experiments, the dynamics remain weakly chaotic, and the instability can be traced to far lower Reynolds numbers than permitted by theory. For increasing inertia, the flow undergoes a transformation to a wall mode composed of inclined near-wall streaks and shear layers. This mode persists to what is known as the "maximum drag reduction limit," and overall EIT is found to dominate viscoelastic flows across more than three orders of magnitude in Reynolds number.}, } @article {pmid34732141, year = {2021}, author = {Zhou, Y and Wang, DM and Liu, L and Huang, P}, title = {The morphometric of lycopsid sporophylls and the evaluation of their dispersal potential: an example from the Upper Devonian of Zhejiang Province, China.}, journal = {BMC ecology and evolution}, volume = {21}, number = {1}, pages = {198}, pmid = {34732141}, issn = {2730-7182}, mesh = {China ; *Fossils ; }, abstract = {BACKGROUND: Previous studies have discussed the special structural adaptations of Late Palaeozoic lycopsids, for example, the dispersal potential of reproductive organs. Based on materials from the Upper Devonian Wutong Formation in Changxing County, Zhejiang Province, China, we now analyze the morphometric and perform some calculation to evaluate the dispersal of sporophyll units of lycopsids.

RESULTS: The fossil sporophyll units are divided into two types in view of obvious difference in shape and we name two new (form) species for them. We also analyze the falling process and give the calculation method of dispersal distance.

CONCLUSIONS: The fossil sporophyll units show relatively poor potential of wind dispersal compared with modern samaras, and show potential adaptation to the turbulent environment.}, } @article {pmid34731319, year = {2021}, author = {Miles, JG and Battista, NA}, title = {Exploring the sensitivity in jellyfish locomotion under variations in scale, frequency, and duty cycle.}, journal = {Journal of mathematical biology}, volume = {83}, number = {5}, pages = {56}, pmid = {34731319}, issn = {1432-1416}, mesh = {Animals ; Biomechanical Phenomena ; Locomotion ; *Models, Biological ; *Scyphozoa ; Swimming ; }, abstract = {Jellyfish have been called one of the most energy-efficient animals in the world due to the ease in which they move through their fluid environment, by product of their bell kinematics coupled with their morphological, muscular, material properties. We investigated jellyfish locomotion by conducting in silico comparative studies and explored swimming performance across different fluid scales (i.e., Reynolds Number), bell contraction frequencies, and contraction phase kinematics (duty cycle) for a jellyfish with a fineness ratio of 1 (ratio of bell height to bell diameter). To study these relationships, an open source implementation of the immersed boundary method was used (IB2d) to solve the fully coupled fluid-structure interaction problem of a flexible jellyfish bell in a viscous fluid. Thorough 2D parameter subspace explorations illustrated optimal parameter combinations in which give rise to enhanced swimming performance. All performance metrics indicated a higher sensitivity to bell actuation frequency than fluid scale or duty cycle, via Sobol sensitivity analysis, on a higher performance parameter subspace. Moreover, Pareto-like fronts were identified in the overall performance space involving the cost of transport and forward swimming speed. Patterns emerged within these performance spaces when highlighting different parameter regions, which complemented the global sensitivity results. Lastly, an open source computational model for jellyfish locomotion is offered to the science community that can be used as a starting place for future numerical experimentation.}, } @article {pmid34693101, year = {2021}, author = {Grande Gutiérrez, N and Shankar, KN and Sinno, T and Diamond, SL}, title = {Thrombosis and Hemodynamics: external and intrathrombus gradients.}, journal = {Current opinion in biomedical engineering}, volume = {19}, number = {}, pages = {}, pmid = {34693101}, issn = {2468-4511}, support = {R01 HL103419/HL/NHLBI NIH HHS/United States ; U01 HL131053/HL/NHLBI NIH HHS/United States ; }, abstract = {Distinct from dilute, isotropic, and homogeneous reaction systems typically used in laboratory kinetic assays, blood is concentrated, two-phase, flowing, and highly anisotropic when clotting on a surface. This review focuses on spatial gradients that are generated and can dictate thrombus structure and function. Novel experimental and computational tools have recently emerged to explore reaction-transport coupling during clotting. Multiscale simulations help bridge tissue length scales (the coronary arteries) to millimeter scales of a growing clot to the microscopic scale of single-cell signaling and adhesion. Microfluidic devices help create and control pathological velocity profiles, albeit at a low Reynolds number. Since rate processes and force loading are often coupled, this review highlights prevailing convective-diffusive transport physics that modulate cellular and molecular processes during thrombus formation.}, } @article {pmid34685088, year = {2021}, author = {Sun, X and Mohammed, HI and Tiji, ME and Mahdi, JM and Majdi, HS and Wang, Z and Talebizadehsardari, P and Yaïci, W}, title = {Investigation of Heat Transfer Enhancement in a Triple Tube Latent Heat Storage System Using Circular Fins with Inline and Staggered Arrangements.}, journal = {Nanomaterials (Basel, Switzerland)}, volume = {11}, number = {10}, pages = {}, pmid = {34685088}, issn = {2079-4991}, abstract = {Inherent fluctuations in the availability of energy from renewables, particularly solar, remain a substantial impediment to their widespread deployment worldwide. Employing phase-change materials (PCMs) as media, saving energy for later consumption, offers a promising solution for overcoming the problem. However, the heat conductivities of most PCMs are limited, which severely limits the energy storage potential of these materials. This study suggests employing circular fins with staggered distribution to achieve improved thermal response rates of PCM in a vertical triple-tube heat exchanger involving two opposite flow streams of the heat-transfer fluid (HTF). Since heat diffusion is not the same at various portions of the PCM unit, different fin configurations, fin dimensions and HTF flow boundary conditions were explored using computational studies of melting in the PCM triple-tube system. Staggered configuration of fin distribution resulted in significant increases in the rates of PCM melting. The results indicate that the melting rate and heat charging rate could be increased by 37.2 and 59.1%, respectively, in the case of staggered distribution. Furthermore, the use of lengthy fins with smaller thickness in the vertical direction of the storage unit resulted in a better positive role of natural convection; thus, faster melting rates were achieved. With fin dimensions of 0.666 mm × 15 mm, the melting rate was found to be increased by 23.6%, when compared to the base case of 2 mm × 5 mm. Finally, it was confirmed that the values of the Reynolds number and inlet temperatures of the HTF had a significant impact on melting time savings when circular fins of staggered distribution were included.}, } @article {pmid34683293, year = {2021}, author = {Yamashita, H and Akinaga, T and Sugihara-Seki, M}, title = {Pattern Transition on Inertial Focusing of Neutrally Buoyant Particles Suspended in Rectangular Duct Flows.}, journal = {Micromachines}, volume = {12}, number = {10}, pages = {}, pmid = {34683293}, issn = {2072-666X}, support = {JP20H02072//JSPS KAKENHI/ ; }, abstract = {The continuous separation and filtration of particles immersed in fluid flows are important interests in various applications. Although the inertial focusing of particles suspended in a duct flow is promising in microfluidics, predicting the focusing positions depending on the parameters, such as the shape of the duct cross-section and the Reynolds number (Re) has not been achieved owing to the diversity of the inertial-focusing phenomena. In this study, we aimed to elucidate the variation of the inertial focusing depending on Re in rectangular duct flows. We performed a numerical simulation of the lift force exerted on a spherical particle flowing in a rectangular duct and determined the lift-force map within the duct cross-section over a wide range of Re. We estimated the particle trajectories based on the lift map and Stokes drag, and identified the particle-focusing points appeared in the cross-section. For an aspect ratio of the duct cross-section of 2, we found that the blockage ratio changes transition structure of particle focusing. For blockage ratios smaller than 0.3, particles focus near the centres of the long sides of the cross-section at low Re and near the centres of both the long and short sides at relatively higher Re. This transition is expressed as a subcritical pitchfork bifurcation. For blockage ratio larger than 0.3, another focusing pattern appears between these two focusing regimes, where particles are focused on the centres of the long sides and at intermediate positions near the corners. Thus, there are three regimes; the transition between adjacent regimes at lower Re is found to be expressed as a saddle-node bifurcation and the other transition as a supercritical pitchfork bifurcation.}, } @article {pmid34678790, year = {2021}, author = {Christov, IC}, title = {Soft hydraulics: from Newtonian to complex fluid flows through compliant conduits.}, journal = {Journal of physics. Condensed matter : an Institute of Physics journal}, volume = {34}, number = {6}, pages = {}, doi = {10.1088/1361-648X/ac327d}, pmid = {34678790}, issn = {1361-648X}, mesh = {Cross-Sectional Studies ; *Hydrodynamics ; Lab-On-A-Chip Devices ; *Microfluidics/methods ; Viscosity ; }, abstract = {Microfluidic devices manufactured from soft polymeric materials have emerged as a paradigm for cheap, disposable and easy-to-prototype fluidic platforms for integrating chemical and biological assays and analyses. The interplay between the flow forces and the inherently compliant conduits of such microfluidic devices requires careful consideration. While mechanical compliance was initially a side-effect of the manufacturing process and materials used, compliance has now become a paradigm, enabling new approaches to microrheological measurements, new modalities of micromixing, and improved sieving of micro- and nano-particles, to name a few applications. This topical review provides an introduction to the physics of these systems. Specifically, the goal of this review is to summarize the recent progress towards a mechanistic understanding of the interaction between non-Newtonian (complex) fluid flows and their deformable confining boundaries. In this context, key experimental results and relevant applications are also explored, hand-in-hand with the fundamental principles for their physics-based modeling. The key topics covered include shear-dependent viscosity of non-Newtonian fluids, hydrodynamic pressure gradients during flow, the elastic response (deformation and bulging) of soft conduits due to flow within, the effect of cross-sectional conduit geometry on the resulting fluid-structure interaction, and key dimensionless groups describing the coupled physics. Open problems and future directions in this nascent field of soft hydraulics, at the intersection of non-Newtonian fluid mechanics, soft matter physics, and microfluidics, are noted.}, } @article {pmid34677517, year = {2021}, author = {Park, NS and Yoon, S and Jeong, W and Jeong, YW}, title = {A Study on the Evaluation of Flow Distribution Evenness in Parallel-Arrayed-Type Low-Pressure Membrane Module Piping.}, journal = {Membranes}, volume = {11}, number = {10}, pages = {}, doi = {10.3390/membranes11100751}, pmid = {34677517}, issn = {2077-0375}, support = {No. 2020R1A2C1006495//National Research Foundation of Korea (NRF)/ ; }, abstract = {The objectives of this study were to measure the flow rate distribution from a header pipe to each module installed in parallel for a water treatment membrane filtration process in operation and to investigate the reason for an uneven distribution of the flow rate via the CFD technique. In addition, this study attempted to propose the ratio of the branch pipe to the header pipe required to equalize the flow distribution for the same membrane filtration process. Finally, the relationship between the Reynolds number in the header pipe and the degree of the manifold flow distribution evenness was investigated. Mobile ultrasonic flow meter was used to measure the flow rate flowing from the membrane module pipe to each module, and the CFD technique was used to verify this. From the results of the actual measurement using ultrasonic flow meter and CFD simulation, it was confirmed that the outflow flow rate from the branch pipe located at the end of the header pipe was three times higher than that of the branch pipe near the inlet. The reason was that the differential pressure generated between each membrane module was higher toward the end of the header pipe. When the ratio of the sum of the cross-sectional area of the branch pipe and the cross-sectional area of the header pipe was reduced by about 30 times, it was confirmed that the flow rate flowing from each branch pipe to the membrane module was almost equal. Also, if the flow in the header pipe is transitional or laminar (Reynolds No. is approximately 4000 or less), the flow rate flowing from each branch pipe to the membrane module can be more even.}, } @article {pmid34677490, year = {2021}, author = {Kim, KT and Park, JE and Jung, SY and Kang, TG}, title = {Fouling Mitigation via Chaotic Advection in a Flat Membrane Module with a Patterned Surface.}, journal = {Membranes}, volume = {11}, number = {10}, pages = {}, pmid = {34677490}, issn = {2077-0375}, support = {2019R1F1A1058001//National Research Foundation of Korea/ ; }, abstract = {Fouling mitigation using chaotic advection caused by herringbone-shaped grooves in a flat membrane module is numerically investigated. The feed flow is laminar with the Reynolds number (Re) ranging from 50 to 500. In addition, we assume a constant permeate flux on the membrane surface. Typical flow characteristics include two counter-rotating flows and downwelling flows, which are highly influenced by the groove depth at each Re. Poincaré sections are plotted to represent the dynamical systems of the flows and to analyze mixing. The flow systems become globally chaotic as the groove depth increases above a threshold value. Fouling mitigation via chaotic advection is demonstrated using the dimensionless average concentration (c¯w*) on the membrane and its growth rate. When the flow system is chaotic, the growth rate of c¯w* drops significantly compared to that predicted from the film theory, demonstrating that chaotic advection is an attractive hydrodynamic technique that mitigates membrane fouling. At each Re, there exists an optimal groove depth minimizing c¯w* and the growth rate of c¯w*. Under the optimum groove geometry, foulants near the membrane are transported back to the bulk flow via the downwelling flows, distributed uniformly in the entire channel via chaotic advection.}, } @article {pmid34663851, year = {2021}, author = {Khan, WU and Imran, A and Raja, MAZ and Shoaib, M and Awan, SE and Kausar, K and He, Y}, title = {A novel mathematical modeling with solution for movement of fluid through ciliary caused metachronal waves in a channel.}, journal = {Scientific reports}, volume = {11}, number = {1}, pages = {20601}, pmid = {34663851}, issn = {2045-2322}, abstract = {In the present research, a novel mathematical model for the motion of cilia using non-linear rheological fluid in a symmetric channel is developed. The strength of analytical perturbation technique is employed for the solution of proposed physical process using mectachoronal rhythm based on Cilia induced flow for pseudo plastic nano fluid model by considering the low Reynolds number and long wave length approximation phenomena. The role of ciliary motion for the fluid transport in various animals is explained. Analytical expressions are gathered for stream function, concentration, temperature profiles, axial velocity, and pressure gradient. Whereas, transverse velocity, pressure rise per wave length, and frictional force on the wall of the tubule are investigated with aid of numerical computations and their outcomes are demonstrated graphically. A comprehensive analysis for comparison of Perturb and numerical solution is done. This analysis validates the analytical solution.}, } @article {pmid34659649, year = {2022}, author = {Cui, PY and Chen, WQ and Wang, JQ and Zhang, JH and Huang, YD and Tao, WQ}, title = {Numerical studies on issues of Re-independence for indoor airflow and pollutant dispersion within an isolated building.}, journal = {Building simulation}, volume = {15}, number = {7}, pages = {1259-1276}, pmid = {34659649}, issn = {1996-3599}, abstract = {This study conducted the numerical models validated by wind-tunnel experiments to investigate the issues of Re-independence of indoor airflow and pollutant dispersion within an isolated building. The window Reynolds number (Re w) was specified to characterize the indoor flow and dispersion. The indicators of RRC (ratio of relative change) or DR (K_DR) (difference ratio of dimensionless concentration) ≤ 5% were applied to quantitatively determine the critical Re w for indoor flow and turbulent diffusion. The results show that the critical Re (Re crit) value is position-dependent, and Re crit at the most unfavorable position should be suggested as the optimal value within the whole areas of interest. Thus Re H,crit = 27,000 is recommended for the outdoor flows; while Re w,crit = 15,000 is determined for the indoor flows due to the lower part below the window showing the most unfavorable. The suggested Re w,crit (=15,000) for indoor airflow and cross ventilation is independence of the window size. Moreover, taking K_DR ≤ 5% as the indicator, the suggested Re w,crit for ensuring indoor pollutant diffusion enter the Re-independence regime should also be 15,000, indicating that indoor passive diffusion is completely determined by the flow structures. The contours of dimensionless velocity (U/U 0) and concentration (K) against the increasing Re w further confirmed this critical value. This study further reveals the Re-independence issues for indoor flow and dispersion to ensure the reliability of the data obtained by reduced-scale numerical or wind-tunnel models.}, } @article {pmid34656560, year = {2022}, author = {Moitoi, AJ and Shaw, S}, title = {Magnetic drug targeting during Caputo-Fabrizio fractionalized blood flow through a permeable vessel.}, journal = {Microvascular research}, volume = {139}, number = {}, pages = {104262}, doi = {10.1016/j.mvr.2021.104262}, pmid = {34656560}, issn = {1095-9319}, mesh = {Antineoplastic Agents/*blood/chemistry/therapeutic use ; Blood Vessels/*metabolism ; Computer Simulation ; *Drug Carriers ; Drug Compounding ; *Magnetic Fields ; *Metal Nanoparticles ; *Models, Cardiovascular ; Nanotechnology ; Neoplasms/*blood supply/drug therapy/metabolism ; Numerical Analysis, Computer-Assisted ; Permeability ; Regional Blood Flow ; }, abstract = {Nanoparticle-based drug targeting is an important platform for the treatment of cardiovascular disorders. Magnetic drug targeting is more significant as it is a noninvasive procedure and biocompatible. The present problem aims to understand magnetic drug delivery to a specific location in a permeable blood vessel under the vibration and magnetic environment. Caputo-Fabrizio fractional-order time derivatives are used in the governing equations. The momentum equations are solved analytically and presented in the form of Lorenzo-Hartley and Robotonov-Hartley functions and convolution of the Laplace transform. Convolution integrations are solved by using the numerical integration technique. The Fourth order Runge-Kutta method (RK4) is used to solve the force balance equation. The influence of pertinent parameters such as Reynolds number, pulsatile frequency, magnetic field strength, Darcy number and fractional-order parameters are presented through graphs. It is observed that increasing Reynolds number results in decreasing the tendency of the drug to capture near the tumor site, whereas the pulsatile frequency presents an opposite phenomenon. Increasing the magnetic field strength and Darcy number boosts the capture efficiency of drug particles near the tumor site. The short memory effect efficiently captures the magnetic drug carriers to a specific location under the action of suitable magnetic field strength.}, } @article {pmid34654198, year = {2021}, author = {Calderer, MC and Golovaty, D and Yao, L and Zhao, L}, title = {Shear flow of active matter in thin channels.}, journal = {Physical review. E}, volume = {104}, number = {3-1}, pages = {034607}, doi = {10.1103/PhysRevE.104.034607}, pmid = {34654198}, issn = {2470-0053}, abstract = {We study the shear flow of active filaments confined in a thin channel for extensile and contractile fibers. We apply the Ericksen-Leslie equations of liquid crystal flow with an activity source term. The dimensionless form of this system includes the Ericksen, activity, and Reynolds numbers, together with the aspect ratio of the channel, as the main driving parameters. We perform a normal mode stability analysis of the base shear flow. For both types of fibers, we arrive at a comprehensive description of the stability properties and their dependence on the parameters of the system. The transition to unstable frequencies in extensile fibers occurs at a positive threshold value of the activity parameter, whereas for contractile ones a complex behavior is found at low absolute value of the activity number. The latter might be an indication of the biologically relevant plasticity and phase transition issues. In contrast with extensile fibers, flows of contractile ones are also found to be highly sensitive to the Reynolds number. The work on extensile fibers is guided by experiments on active filaments in confined channels and aims at quantifying their findings in the prechaotic regime.}, } @article {pmid34651149, year = {2021}, author = {Gallen, AF and Castro, M and Hernandez-Machado, A}, title = {Red blood cells in low Reynolds number flow: A vorticity-based characterization of shapes in two dimensions.}, journal = {Soft matter}, volume = {17}, number = {42}, pages = {9587-9594}, doi = {10.1039/d1sm00559f}, pmid = {34651149}, issn = {1744-6848}, mesh = {Cell Movement ; Cell Shape ; *Erythrocytes ; *Hydrodynamics ; Physical Phenomena ; }, abstract = {Studies on the mechanical properties of red blood cells improve the diagnosis of some blood-related diseases. Some existing numerical methods have successfully simulated the coupling between a fluid and red blood cells. This paper introduces an alternative phase-field model formulation of two-dimensional cells that solves the vorticity and stream function that simplifies the numerical implementation. We integrate red blood cell dynamics immersed in a Poiseuille flow and reproduce previously reported morphologies (slippers or parachutes). In the case of flow in a very wide channel, we discover a new metastable shape referred to as 'anti-parachute' that evolves into a horizontal slipper centered on the channel. This sort of metastable morphology may contribute to the dynamical response of the blood.}, } @article {pmid34644682, year = {2022}, author = {Truong, H and Engels, T and Wehmann, H and Kolomenskiy, D and Lehmann, FO and Schneider, K}, title = {An experimental data-driven mass-spring model of flexibleCalliphorawings.}, journal = {Bioinspiration & biomimetics}, volume = {17}, number = {2}, pages = {}, doi = {10.1088/1748-3190/ac2f56}, pmid = {34644682}, issn = {1748-3190}, mesh = {Animals ; Biomechanical Phenomena ; Elasticity ; *Flight, Animal ; Humans ; Insecta ; Models, Biological ; *Wings, Animal ; }, abstract = {Insect wings can undergo significant deformation during flapping motion owing to inertial, elastic and aerodynamic forces. Changes in shape then alter aerodynamic forces, resulting in a fully coupled fluid-structure interaction (FSI) problem. Here, we present detailed three-dimensional FSI simulations of deformable blowfly (Calliphora vomitoria) wings in flapping flight. A wing model is proposed using a multi-parameter mass-spring approach, chosen for its implementation simplicity and computational efficiency. We train the model to reproduce static elasticity measurements by optimizing its parameters using a genetic algorithm with covariance matrix adaptation (CMA-ES). Wing models trained with experimental data are then coupled to a high-performance flow solver run on massively parallel supercomputers. Different features of the modeling approach and the intra-species variability of elastic properties are discussed. We found that individuals with different wing stiffness exhibit similar aerodynamic properties characterized by dimensionless forces and power at the same Reynolds number. We further study the influence of wing flexibility by comparing between the flexible wings and their rigid counterparts. Under equal prescribed kinematic conditions for rigid and flexible wings, wing flexibility improves lift-to-drag ratio as well as lift-to-power ratio and reduces peak force observed during wing rotation.}, } @article {pmid34642447, year = {2021}, author = {Ali, A and Kanwal, T and Awais, M and Shah, Z and Kumam, P and Thounthong, P}, title = {Impact of thermal radiation and non-uniform heat flux on MHD hybrid nanofluid along a stretching cylinder.}, journal = {Scientific reports}, volume = {11}, number = {1}, pages = {20262}, pmid = {34642447}, issn = {2045-2322}, abstract = {The current research investigates the thermal radiations and non-uniform heat flux impacts on magnetohydrodynamic hybrid nanofluid (CuO-Fe2O3/H2O) flow along a stretching cylinder, which is the main aim of this study. The velocity slip conditions have been invoked to investigate the slippage phenomenon on the flow. The impact of induced magnetic field with the assumption of low Reynolds number is imperceptible. Through the use of appropriate non-dimensional parameters and similarity transformations, the ruling PDE's (partial differential equations) are reduced to set of ODE's (ordinary differential equations), which are then numerically solved using Adams-Bashforth Predictor-Corrector method. Velocity and temperature fields with distinct physical parameters are investigated and explored graphically. The main observations about the hybrid nanofluid and non-uniform heat flux are analyzed graphically. A decrease in the velocity of the fluid is noted with addition of Hybrid nanofluid particles while temperature of the fluid increases by adding the CuO-Fe2O3 particles to the base fluid. Also, velocity of the fluid decreases when we incorporate the effects of magnetic field and slip. Raise in curvature parameter γ caused enhancement of velocity and temperature fields at a distance from the cylinder but displays opposite behavior nearby the surface of cylinder. The existence of heat generation and absorption for both mass dependent and time dependent parameters increases the temperature of the fluid.}, } @article {pmid34636830, year = {2021}, author = {Ho, TM and Yang, J and Tsai, PA}, title = {Microfluidic mass transfer of CO2 at elevated pressures: implications for carbon storage in deep saline aquifers.}, journal = {Lab on a chip}, volume = {21}, number = {20}, pages = {3942-3951}, doi = {10.1039/d1lc00106j}, pmid = {34636830}, issn = {1473-0189}, mesh = {*Carbon Dioxide ; *Groundwater ; Microfluidics ; Water ; }, abstract = {Carbon capture and sequestration (CCS) in a deep saline aquifer is one of the most promising technologies to mitigate anthropologically emitted carbon dioxide. Accurately quantifying the mass transport of CO2 at pore-scales is crucial but challenging for successful CCS deployment. Here, we conduct high-pressure microfluidic experiments, mimicking reservoir conditions up to 9.5 MPa and 35 °C, to elucidate the microfluidic mass transfer process of CO2 at three different states (i.e., gas, liquid, and supercritical phase) into water. We measure the size change of CO2 micro-bubbles/droplets generated using a microfluidic T-junction to estimate the volumetric mass transfer coefficient (kLa), quantifying the rate change of CO2 concentration under the driving force of concentration gradient. The results show that bubbles/droplets under high-pressure conditions reach a steady state faster than low pressure. The measured volumetric mass transfer coefficient increases with the Reynolds number (based on the liquid slug) and is nearly independent of the injection pressure for both the gas and liquid phases. In addition, kLa significantly enlarges with increasing high pressure at the supercritical state. Compared with various chemical engineering applications using millimeter-sized capillaries (with typical kLa measured ranging from ≈0.005 to 0.8 s-1), the microfluidic results show a significant increase in the volumetric mass transfer of CO2 into water by two to three orders of magnitude, O (102-103), with decreasing hydrodynamic diameter (of ≈50 μm).}, } @article {pmid34635693, year = {2021}, author = {Liao, Y and Mechulam, Y and Lassalle-Kaiser, B}, title = {A millisecond passive micromixer with low flow rate, low sample consumption and easy fabrication.}, journal = {Scientific reports}, volume = {11}, number = {1}, pages = {20119}, pmid = {34635693}, issn = {2045-2322}, mesh = {Complex Mixtures/*analysis ; *Computer Simulation ; Equipment Design ; Humans ; Lab-On-A-Chip Devices/*standards ; Microfluidic Analytical Techniques/*instrumentation/*methods ; }, abstract = {Fast mixing of small volumes of solutions in microfluidic devices is essential for an accurate control and observation of the dynamics of a reaction in biological or chemical studies. It is often, however, a challenging task, as the Reynolds number (Re) in microscopic devices is typically < 100. In this report, we detail a novel mixer based on the "staggered herring bone" (SHB) pattern and "split-recombination" strategies with an optimized geometry, the periodic rotation of the flow structure can be controlled and recombined in a way that the vortices and phase shifts of the flow induce intertwined lamellar structures, thus increasing the contact surface and enhancing mixing. The optimization improves the mixing while using a low flow rate, hence a small volume for mixing and moderate pressure drops. The performances of the patterns were first simulated using COMSOL Multiphysics under different operating conditions. The simulation indicates that at very low flow rate (1-12 µL·min-1) and Re (3.3-40), as well as a very small working volume (~ 3 nL), a very good mixing (~ 98%) can be achieved in the ms time range (4.5-78 ms). The most promising design was then visualized experimentally, showing results that are consistent with the outcomes of the simulations. Importantly, the devices were fabricated using a classical soft-lithography method, as opposed to additive manufacturing often used to generate complex mixing structures. This new device minimizes the sample consumption and could therefore be applied for studies using precious samples.}, } @article {pmid34625588, year = {2021}, author = {Hussain, A and Hassan, A and Mdallal, QA and Ahmad, H and Sherif, EM and Rehman, A and Arshad, M}, title = {Comsolic solution of an elliptic cylindrical compressible fluid flow.}, journal = {Scientific reports}, volume = {11}, number = {1}, pages = {20030}, pmid = {34625588}, issn = {2045-2322}, abstract = {In this article, the primary focus is to investigate the heat transfer effects with viscous compressible laminar flow in the permeable elliptic cylinder. The Reynolds number is kept 100 for flow to be laminar. The physics of heat transfer is selected to be coupled with the laminar flow. The results for particular step-size time for Velocity distribution, pressure profile, temperature profile, isothermal temperature contours, and drag coefficient have been analyzed. Mesh has been generated through COMSOL, mesh entities have been elaborated statistically. The maximum and minimum velocity profile is observed at the elliptical cylinder's walls and upper, lower boundary respectively. The maximum velocity observed is 2.22 m/s. Pressure profile around elliptic corners is found maximum, distinct patterns are observed even under the influence of applied heat. Temperature is observed maximum at walls but it gradually increases as moving from the upper boundary towards the lower boundary. The isothermal contour patterns are observed maximum near the walls, drag coefficient of gradual decrease is observed. COMSOL multi-physics is utilized for mathematical modeling of problems and the Backward-Differentiation-Formula has been exploited to handle problems numerically. The results will help greatly to understand the characterizations of viscous fluids and in industries like air furnaces and automobile cooling systems.}, } @article {pmid34623848, year = {2021}, author = {Khalid, M and Shankar, V and Subramanian, G}, title = {Continuous Pathway between the Elasto-Inertial and Elastic Turbulent States in Viscoelastic Channel Flow.}, journal = {Physical review letters}, volume = {127}, number = {13}, pages = {134502}, doi = {10.1103/PhysRevLett.127.134502}, pmid = {34623848}, issn = {1079-7114}, abstract = {Viscoelastic plane Poiseuille flow is shown to become linearly unstable in the absence of inertia, in the limit of high elasticities, for ultradilute polymer solutions. While inertialess elastic instabilities have been predicted for curvilinear shear flows, this is the first ever report of a purely elastic linear instability in a rectilinear shear flow. The novel instability continues up to a Reynolds number (Re) of O(1000), corresponding to the recently identified elasto-inertial turbulent state believed to underlie the maximum-drag-reduced regime. Thus, for highly elastic ultradilute polymer solutions, a single linearly unstable modal branch may underlie transition to elastic turbulence at zero Re and to elasto-inertial turbulence at moderate Re, implying the existence of continuous pathways connecting the turbulent states to each other and to the laminar base state.}, } @article {pmid34608161, year = {2021}, author = {Marusic, I and Chandran, D and Rouhi, A and Fu, MK and Wine, D and Holloway, B and Chung, D and Smits, AJ}, title = {An energy-efficient pathway to turbulent drag reduction.}, journal = {Nature communications}, volume = {12}, number = {1}, pages = {5805}, pmid = {34608161}, issn = {2041-1723}, abstract = {Simulations and experiments at low Reynolds numbers have suggested that skin-friction drag generated by turbulent fluid flow over a surface can be decreased by oscillatory motion in the surface, with the amount of drag reduction predicted to decline with increasing Reynolds number. Here, we report direct measurements of substantial drag reduction achieved by using spanwise surface oscillations at high friction Reynolds numbers ([Formula: see text]) up to 12,800. The drag reduction occurs via two distinct physical pathways. The first pathway, as studied previously, involves actuating the surface at frequencies comparable to those of the small-scale eddies that dominate turbulence near the surface. We show that this strategy leads to drag reduction levels up to 25% at [Formula: see text] = 6,000, but with a power cost that exceeds any drag-reduction savings. The second pathway is new, and it involves actuation at frequencies comparable to those of the large-scale eddies farther from the surface. This alternate pathway produces drag reduction of 13% at [Formula: see text] = 12,800. It requires significantly less power and the drag reduction grows with Reynolds number, thereby opening up potential new avenues for reducing fuel consumption by transport vehicles and increasing power generation by wind turbines.}, } @article {pmid34607142, year = {2022}, author = {Yogarathinam, LT and Velswamy, K and Gangasalam, A and Ismail, AF and Goh, PS and Narayanan, A and Abdullah, MS}, title = {Performance evaluation of whey flux in dead-end and cross-flow modes via convolutional neural networks.}, journal = {Journal of environmental management}, volume = {301}, number = {}, pages = {113872}, doi = {10.1016/j.jenvman.2021.113872}, pmid = {34607142}, issn = {1095-8630}, mesh = {*Cheese/analysis ; Filtration ; Membranes, Artificial ; Neural Networks, Computer ; *Whey ; Whey Proteins ; }, abstract = {Effluent originating from cheese production puts pressure onto environment due to its high organic load. Therefore, the main objective of this work was to compare the influence of different process variables (transmembrane pressure (TMP), Reynolds number and feed pH) on whey protein recovery from synthetic and industrial cheese whey using polyethersulfone (PES 30 kDa) membrane in dead-end and cross-flow modes. Analysis on the fouling mechanistic model indicates that cake layer formation is dominant as compared to other pore blocking phenomena evaluated. Among the input variables, pH of whey protein solution has the biggest influence towards membrane flux and protein rejection performances. At pH 4, electrostatic attraction experienced by whey protein molecules prompted a decline in flux. Cross-flow filtration system exhibited a whey rejection value of 0.97 with an average flux of 69.40 L/m2h and at an experimental condition of 250 kPa and 8 for TMP and pH, respectively. The dynamic behavior of whey effluent flux was modeled using machine learning (ML) tool convolutional neural networks (CNN) and recursive one-step prediction scheme was utilized. Linear and non-linear correlation indicated that CNN model (R2 - 0.99) correlated well with the dynamic flux experimental data. PES 30 kDa membrane displayed a total protein rejection coefficient of 0.96 with 55% of water recovery for the industrial cheese whey effluent. Overall, these filtration studies revealed that this dynamic whey flux data studies using the CNN modeling also has a wider scope as it can be applied in sensor tuning to monitor flux online by means of enhancing whey recovery efficiency.}, } @article {pmid34599248, year = {2021}, author = {Almalki, MM and Alaidarous, ES and Maturi, DA and Raja, MAZ and Shoaib, M}, title = {Intelligent computing technique based supervised learning for squeezing flow model.}, journal = {Scientific reports}, volume = {11}, number = {1}, pages = {19597}, pmid = {34599248}, issn = {2045-2322}, abstract = {In this study, the unsteady squeezing flow between circular parallel plates (USF-CPP) is investigated through the intelligent computing paradigm of Levenberg-Marquard backpropagation neural networks (LMBNN). Similarity transformation introduces the fluidic system of the governing partial differential equations into nonlinear ordinary differential equations. A dataset is generated based on squeezing fluid flow system USF-CPP for the LMBNN through the Runge-Kutta method by the suitable variations of Reynolds number and volume flow rate. To attain approximation solutions for USF-CPP to different scenarios and cases of LMBNN, the operations of training, testing, and validation are prepared and then the outcomes are compared with the reference data set to ensure the suggested model's accuracy. The output of LMBNN is discussed by the mean square error, dynamics of state transition, analysis of error histograms, and regression illustrations.}, } @article {pmid34588473, year = {2021}, author = {Ramzan, M and Khan, NS and Kumam, P}, title = {Mechanical analysis of non-Newtonian nanofluid past a thin needle with dipole effect and entropic characteristics.}, journal = {Scientific reports}, volume = {11}, number = {1}, pages = {19378}, pmid = {34588473}, issn = {2045-2322}, abstract = {The study concerns with the mechanical characteristics of heat and mass transfer flow of a second grade nanofluid as well as gyrotatic microorganism motion past a thin needle with dipole effect, entropy generation, thermal radiation, Arrhenius activation energy and binar chemical reaction. The governing equations and boundary conditions are simplified by the use of suitable similarity transformations. Homotopy analysis method is implemented to obtain the series solution of non-linear ordinary differential equations. Physical behaviors of heat and mass transfer flow with gyrotatic microorganisms and entropy generation are investigated through the embedded parameters. The nanofluid velocity is enhanced for higher values of the ferromagnetic parameter, local Grashof number, bioconvection Rayleigh number and radiation parameter. The Reynolds number, radiation parameter and Eckert number decrease the nanofluid temperature. The entropy generation is increased with the enhancement of radiation parameter, Eckert number, Lewis number, temperature difference parameter, dimensionless constant parameter, Curie temperature, Prandtl number and concentration difference parameter.}, } @article {pmid34586089, year = {2021}, author = {Treiser, MD and Miles, MR and Albino, FP and Giladi, AM and Katz, RD and Higgins, JP}, title = {Long-Term Patency and Fluid Dynamics of Recipient Artery after End-to-Side Anastomosis for Free Tissue Transfer.}, journal = {Plastic and reconstructive surgery}, volume = {148}, number = {5}, pages = {800e-803e}, doi = {10.1097/PRS.0000000000008439}, pmid = {34586089}, issn = {1529-4242}, mesh = {Adolescent ; Adult ; Anastomosis, Surgical/methods ; Arteries/diagnostic imaging/physiology/*surgery ; Blood Flow Velocity ; Collateral Circulation ; Extremities/blood supply/*injuries/surgery ; Follow-Up Studies ; Free Tissue Flaps/blood supply/*transplantation ; Humans ; Middle Aged ; Reconstructive Surgical Procedures/*methods ; Treatment Outcome ; Ultrasonography, Doppler, Duplex ; *Vascular Patency ; Young Adult ; }, abstract = {BACKGROUND: End-to-end microvascular anastomoses sacrifice downstream inline perfusion of the recipient vessels. End-to-side anastomoses, in theory, maintain distal inline flow of the recipient vessel. The proposed benefit of the end-to-side technique depends on patency of the distal vessels and subsequent flow parameters, but maintenance of distal perfusion has not been conclusively demonstrated.

METHODS: Fifteen patients who underwent a successful extremity free flap procedure via end-to-side anastomoses to a noncritical vessel between 2003 and 2017 were enrolled. Recipient artery patency distal to the anastomosis was assessed using pulse volume recordings and duplex ultrasound imaging. Resistance indices, flow velocities, vessel diameters, volumetric flow, and turbulent flow dimensionless number (Reynolds number) were measured. Comparisons were made to the ipsilateral collateral vessel as well as to the vessels on the nonoperative contralateral limb using paired t tests.

RESULTS: Downstream flow was identified in 14 of 15 patients (93 percent patency). There was no statistical difference in resistive indices comparing the anastomotic vessel (0.859 ± 0.300) and the collateral vessel (0.853 ± 0.179) of the ipsilateral extremity. Ultrasound flows were similar; the anastomotic vessel demonstrated downstream volumetric flows of 139 ± 92.0 cm3/min versus 137 ± 41.6 cm3/min within the same vessel of the nonoperative contralateral limb. The anastomotic vessel had Reynolds numbers well below the turbulent threshold (448 ± 202 and 493 ± 127 for the anastomotic and nonoperative contralateral limb, respectively).

CONCLUSION: End-to-side anastomosis to noncritical vessels resulted in a 93 percent long-term recipient vessel patency rate, with no statistically significant changes in volumetric flows, resistive indices, or fluid dynamics in the vessels that remained patent.}, } @article {pmid34577719, year = {2021}, author = {Huang, L and Du, J and Zhu, Z}, title = {Neutrally Buoyant Particle Migration in Poiseuille Flow Driven by Pulsatile Velocity.}, journal = {Micromachines}, volume = {12}, number = {9}, pages = {}, pmid = {34577719}, issn = {2072-666X}, support = {11572107//National Natural Science Foundation of China/ ; GK199900299012-026//the Fundamental Research Funds for the Provincial Universities of Zhejiang/ ; }, abstract = {A neutrally buoyant circular particle migration in two-dimensional (2D) Poiseuille channel flow driven by pulsatile velocity is numerical studied by using immersed boundary-lattice Boltzmann method (IB-LBM). The effects of Reynolds number (25≤Re≤200) and blockage ratio (0.15≤k≤0.40) on particle migration driven by pulsatile and non-pulsatile velocity are all numerically investigated for comparison. The results show that, different from non-pulsatile cases, the particle will migrate back to channel centerline with underdamped oscillation during the time period with zero-velocity in pulsatile cases. The maximum lateral travel distance of the particle in one cycle of periodic motion will increase with increasing Re, while k has little impact. The quasi frequency of such oscillation has almost no business with Re and k. Moreover, Re plays an essential role in the damping ratio. Pulsatile flow field is ubiquitous in aorta and other arteries. This article is conducive to understanding nanoparticle migration in those arteries.}, } @article {pmid34577699, year = {2021}, author = {Farahinia, A and Jamaati, J and Niazmand, H and Zhang, W}, title = {Numerical Analysis of the Heterogeneity Effect on Electroosmotic Micromixers Based on the Standard Deviation of Concentration and Mixing Entropy Index.}, journal = {Micromachines}, volume = {12}, number = {9}, pages = {}, pmid = {34577699}, issn = {2072-666X}, abstract = {One approach to achieve a homogeneous mixture in microfluidic systems in the quickest time and shortest possible length is to employ electroosmotic flow characteristics with heterogeneous surface properties. Mixing using electroosmotic flow inside microchannels with homogeneous walls is done primarily under the influence of molecular diffusion, which is not strong enough to mix the fluids thoroughly. However, surface chemistry technology can help create desired patterns on microchannel walls to generate significant rotational currents and improve mixing efficiency remarkably. This study analyzes the function of a heterogeneous zeta-potential patch located on a microchannel wall in creating mixing inside a microchannel affected by electroosmotic flow and determines the optimal length to achieve the desired mixing rate. The approximate Helmholtz-Smoluchowski model is suggested to reduce computational costs and simplify the solving process. The results show that the heterogeneity length and location of the zeta-potential patch affect the final mixing proficiency. It was also observed that the slip coefficient on the wall has a more significant effect than the Reynolds number change on improving the mixing efficiency of electroosmotic micromixers, benefiting the heterogeneous distribution of zeta-potential. In addition, using a channel with a heterogeneous zeta-potential patch covered by a slip surface did not lead to an adequate mixing in low Reynolds numbers. Therefore, a homogeneous channel without any heterogeneity would be a priority in such a range of Reynolds numbers. However, increasing the Reynolds number and the presence of a slip coefficient on the heterogeneous channel wall enhances the mixing efficiency relative to the homogeneous one. It should be noted, though, that increasing the slip coefficient will make the mixing efficiency decrease sharply in any situation, especially in high Reynolds numbers.}, } @article {pmid34575038, year = {2021}, author = {Gimsa, J and Gimsa, U}, title = {Contributions to a Discussion of Spinosaurus aegyptiacus as a Capable Swimmer and Deep-Water Predator.}, journal = {Life (Basel, Switzerland)}, volume = {11}, number = {9}, pages = {}, pmid = {34575038}, issn = {2075-1729}, abstract = {The new findings on Spinosaurus' swim tail strongly suggest that Spinosaurus was a specialized deep-water predator. However, the tail must be seen in the context of the propelled body. The comparison of the flow characteristics of Spinosaurus with geometrically similar animals and their swimming abilities under water must take their Reynolds numbers into account and provide a common context for the properties of Spinosaurus' tail and dorsal sail. Head shape adaptations such as the head crest reduced hydrodynamic disturbance and facilitated stealthy advance, especially when hunting without visual contact, when Spinosaurus could have used its rostral integumentary mechanoreceptors for prey detection. The muscular neck permitted 'pivot' feeding, where the prey's escape abilities were overcome by rapid dorsoventral head movement, facilitated by crest-mediated lower friction.}, } @article {pmid34549120, year = {2021}, author = {Wu, R and Xie, F and Wei, J and Song, X and Yang, H and Lv, P and Yu, G}, title = {Study on Soot Emission Characteristics of Methane/Oxygen Inverse Diffusion Flame.}, journal = {ACS omega}, volume = {6}, number = {36}, pages = {23191-23202}, pmid = {34549120}, issn = {2470-1343}, abstract = {Inverse diffusion flame (IDF) is an effective and widely used reaction form in the process of noncatalytic partial oxidation (NC-POX) of gaseous hydrocarbons (such as natural gas and coke oven gas). However, soot is generated in the combustion chamber in the case of unreasonable feeding conditions, and thus causes serious damage to the wall and nozzle. In this study, the effects of the equivalence ratio ([O/C]e), the oxygen flow rate, and the Reynolds number on the soot and CH* emission characteristics of CH4/O2 inverse diffusion flame were comprehensively analyzed based on a hyperspectral imaging system. In addition, the relationship between CH* and soot is explored using Ansys Fluent simulation. The experimental results show that the soot radiation core generation area is located in the outer ring of the flame, and the radial distribution of the radiation intensity is bimodal. With the increase in [O/C]e, the initial position for soot radiation and the overall radiation intensity of soot decrease. In addition, the CH* radiation intensity decreases as [O/C]e increases, and CH* exists in the whole flame. The simulation results clearly show that the existence of CH* is conducive to soot production. The emission intensity and the core area of soot formation increase with the increase in the oxygen velocity. Additionally, the soot emission region increases and the flame tip changes from a round blunt to symmetrical tip with the increase in the Reynolds number.}, } @article {pmid34547732, year = {2021}, author = {Haider, N and Shahzad, A and Qadri, MNM and Shams, TA}, title = {Aerodynamic analysis of hummingbird-like hovering flight.}, journal = {Bioinspiration & biomimetics}, volume = {16}, number = {6}, pages = {}, doi = {10.1088/1748-3190/ac28eb}, pmid = {34547732}, issn = {1748-3190}, mesh = {Animals ; Biomechanical Phenomena ; Birds ; Computer Simulation ; *Flight, Animal ; Insecta ; Models, Biological ; *Wings, Animal ; }, abstract = {Flapping wing micro aerial vehicles are studied as the substitute for fixed and rotary wing micro aerial vehicles because of the advantages such as agility, maneuverability, and employability in confined environments. Hummingbird's sustainable hovering capability inspires many researchers to develop micro aerial vehicles with similar dynamics. In this research, a wing of a ruby-throated hummingbird is modeled as an insect wing using membrane and stiffeners. The effect of flexibility on the aerodynamic performance of a wing in hovering flight has been studied numerically by using a fluid-structure interaction scheme at a Reynolds number of 3000. Different wings have been developed by using different positions and thicknesses of the stiffeners. The chordwise and spanwise flexural stiffnesses of all the wings modeled in this work are comparable to insects of similar span and chord length. When the position of the stiffener is varied, the best-performing wing has an average lift coefficient of 0.51. Subsequently, the average lift coefficient is increased to 0.56 when the appropriate thickness of the stiffeners is chosen. The best flexible wing outperforms its rigid counterpart and produces lift and power economy comparable to a real hummingbird's wing. That is, the average lift coefficient and power economy of 0.56 and 0.88 for the best flexible wing as compared to 0.61 and 1.07 for the hummingbird's wing. It can be concluded that a simple manufacturable flexible wing design based on appropriate positioning and thickness of stiffeners can serve as a potential candidate for bio-inspired flapping-wing micro aerial vehicles.}, } @article {pmid34528156, year = {2021}, author = {Javid, K and Hassan, M and Tripathi, D and Khan, S and Bobescu, E and Bhatti, MM}, title = {Double-diffusion convective biomimetic flow of nanofluid in a complex divergent porous wavy medium under magnetic effects.}, journal = {Journal of biological physics}, volume = {47}, number = {4}, pages = {477-498}, pmid = {34528156}, issn = {1573-0689}, mesh = {*Biomimetics ; Diffusion ; *Magnetic Fields ; *Nanotechnology ; Porosity ; }, abstract = {We explore the physical influence of magnetic field on double-diffusive convection in complex biomimetic (peristaltic) propulsion of nanofluid through a two-dimensional divergent channel. Additionally, porosity effects along with rheological properties of the fluid are also retained in the analysis. The mathematical model is developed by equations of continuity, momentum, energy, and mass concentration. First, scaling analysis is introduced to simplify the rheological equations in the wave frame of reference and then get the final form of equations after applying the low Reynolds number and lubrication approach. The obtained equations are solved analytically by using integration method. Physical interpretation of velocity, pressure gradient, pumping phenomena, trapping phenomena, heat, and mass transfer mechanisms are discussed in detail under magnetic and porous environment. The magnitude of velocity profile is reduced by increasing Grashof parameter. The bolus circulations disappeared from trapping phenomena for larger strength of magnetic and porosity medium. The magnitude of temperature profile and mass concentration are increasing by enhancing the Brownian motion parameter. This study can be productive in manufacturing non-uniform and divergent shapes of micro-lab-chip devices for thermal engineering, industrial, and medical technologies.}, } @article {pmid34505131, year = {2022}, author = {Costa, RP and Simplice Talla Nwotchouang, B and Yao, J and Biswas, D and Casey, D and McKenzie, R and Steinman, DA and Loth, F}, title = {Transition to Turbulence Downstream of a Stenosis for Whole Blood and a Newtonian Analog Under Steady Flow Conditions.}, journal = {Journal of biomechanical engineering}, volume = {144}, number = {3}, pages = {}, doi = {10.1115/1.4052370}, pmid = {34505131}, issn = {1528-8951}, mesh = {Animals ; Blood Flow Velocity ; Constriction, Pathologic ; *Glycerol ; *Models, Cardiovascular ; Rheology ; Stress, Mechanical ; Swine ; Water ; }, abstract = {Blood, a multiphase fluid comprised of plasma, blood cells, and platelets, is known to exhibit a shear-thinning behavior at low shear rates and near-Newtonian behavior at higher shear rates. However, less is known about the impact of its multiphase nature on the transition to turbulence. In this study, we experimentally determined the critical Reynolds number at which the flow began to transition to turbulence downstream of eccentric stenosis for whole porcine blood and a Newtonian blood analog (water-glycerin mixture). Velocity profiles for both fluids were measured under steady-state flow conditions using an ultrasound Doppler probe placed 12 diameters downstream of eccentric stenosis. Velocity was recorded at 21 locations along the diameter at 11 different flow rates. Normalized turbulent kinetic energy was used to determine the critical Reynolds number for each fluid. Blood rheology was measured before and after each experiment. Tests were conducted on five samples of each fluid inside a temperature-controlled in vitro flow system. The viscosity at a shear rate of 1000 s-1 was used to define the Reynolds number for each fluid. The mean critical Reynolds numbers for blood and water-glycerin were 470 ± 27.5 and 395 ± 10, respectively, indicating a ∼19% delay in transition to turbulence for whole blood compared to the Newtonian fluid. This finding is consistent with a previous report for steady flow in a straight pipe, suggesting some aspect of blood rheology may serve to suppress, or at least delay, the onset of turbulence in vivo.}, } @article {pmid34497885, year = {2021}, author = {Bu, X and Zhou, S and Sun, M and Alheshibri, M and Khan, MS and Xie, G and Chelgani, SC}, title = {Exploring the Relationships between Gas Dispersion Parameters and Differential Pressure Fluctuations in a Column Flotation.}, journal = {ACS omega}, volume = {6}, number = {34}, pages = {21900-21908}, pmid = {34497885}, issn = {2470-1343}, abstract = {Flotation separation, which is the most important mineral beneficiation technique, is dependent on gas dispersion (hydrodynamic conditions). Thus, many investigations have focused on the precise determination of hydrodynamic conditions such as Reynolds number of the bubbles, bubble velocity, and bubble diameter. However, few studies have examined their relationships with pressure fluctuations in a column flotation. This study introduced the differential pressure fluctuations as an actual variable that could be considered to determine the collection zone's hydrodynamic conditions in a cyclonic microbubble flotation column. In general, the outcomes indicated that superficial gas velocity had the most substantial relationship with the differential pressure fluctuations among other flotation factors (such as pump speed, superficial gas velocity, superficial water velocity, and frother dosage). Furthermore, a high coefficient of determination (R 2 > 0.77) for the equation generated to assess the relationships demonstrated that differential pressure fluctuations could be used as a promising tool to determine the hydrodynamic parameters' characteristics in the flotation columns.}, } @article {pmid34497293, year = {2021}, author = {Aghamiri, H and Niknejadi, M and Toghraie, D}, title = {Analysis of the forced convection of two-phase Ferro-nanofluid flow in a completely porous microchannel containing rotating cylinders.}, journal = {Scientific reports}, volume = {11}, number = {1}, pages = {17811}, pmid = {34497293}, issn = {2045-2322}, abstract = {In the present work, the forced convection of nanofluid flow in a microchannel containing rotating cylinders is investigated in different geometries. The heat flux applied to the microchannel wall is 10,000 W m-2. The effects of Reynolds number, the volume fraction of nanoparticles, and the porosity percentage of the porous medium are investigated on the flow fields, temperature, and heat transfer rate. Reynolds number values vary from Re = 250-1000, non-dimensional rotational velocities 1 and 2, respectively, and volume fraction of nanoparticles 0-2%. The results show that increasing the velocity of rotating cylinders increases the heat transfer; also, increasing the Reynolds number and volume fraction of nanoparticles increases the heat transfer, pressure drop, and Cf,ave. By comparing the porosity percentages with each other, it is concluded that due to the greater contact of the nanofluid with the porous medium and the creation of higher velocity gradients, the porosity percentage is 45% and the values of are 90% higher than the porosity percentage. Comparing porosity percentages with each other, at porosity percentage 90% is greater than at porosity percentage 45%. On the other hand, increasing the Reynolds number reduces the entropy generation due to heat transfer and increases the entropy generation due to friction. Increasing the volume fraction of nanoparticles increases the entropy generations due to heat transfer and friction.}, } @article {pmid34482836, year = {2021}, author = {Mandell, JG and Loke, YH and Mass, PN and Cleveland, V and Delaney, M and Opfermann, J and Aslan, S and Krieger, A and Hibino, N and Olivieri, LJ}, title = {Altered hemodynamics by 4D flow cardiovascular magnetic resonance predict exercise intolerance in repaired coarctation of the aorta: an in vitro study.}, journal = {Journal of cardiovascular magnetic resonance : official journal of the Society for Cardiovascular Magnetic Resonance}, volume = {23}, number = {1}, pages = {99}, pmid = {34482836}, issn = {1532-429X}, support = {R01 HL143468/HL/NHLBI NIH HHS/United States ; R38 AI140298/AI/NIAID NIH HHS/United States ; R38AI140298/AI/NIAID NIH HHS/United States ; R01HL143468-0/HL/NHLBI NIH HHS/United States ; }, mesh = {Aorta ; Aorta, Thoracic/diagnostic imaging/surgery ; *Aortic Coarctation/diagnostic imaging/surgery ; Blood Flow Velocity ; Hemodynamics ; Humans ; Magnetic Resonance Spectroscopy ; Predictive Value of Tests ; Retrospective Studies ; }, abstract = {BACKGROUND: Coarctation of the aorta (CoA) is associated with decreased exercise capacity despite successful repair. Altered flow patterns have been identified due to abnormal aortic arch geometry. Our previous work demonstrated aorta size mismatch to be associated with exercise intolerance in this population. In this study, we studied aortic flow patterns during simulations of exercise in repaired CoA using 4D flow cardiovascular magnetic resonance (CMR) using aortic replicas connected to an in vitro flow pump and correlated findings with exercise stress test results to identify biomarkers of exercise intolerance.

METHODS: Patients with CoA repair were retrospectively analyzed after CMR and exercise stress test. Each aorta was manually segmented and 3D printed. Pressure gradient measurements from ascending aorta (AAo) to descending aorta (DAo) and 4D flow CMR were performed during simulations of rest and exercise using a mock circulatory flow loop. Changes in wall shear stress (WSS) and secondary flow formation (vorticity and helicity) from rest to exercise were quantified, as well as estimated DAo Reynolds number. Parameters were correlated with percent predicted peak oxygen consumption (VO2max) and aorta size mismatch (DAAo/DDAo).

RESULTS: Fifteen patients were identified (VO2max 47 to 126% predicted). Pressure gradient did not correlate with VO2max at rest or exercise. VO2max correlated positively with the change in peak vorticity (R = 0.55, p = 0.03), peak helicity (R = 0.54, p = 0.04), peak WSS in the AAo (R = 0.68, p = 0.005) and negatively with peak WSS in the DAo (R = - 0.57, p = 0.03) from rest to exercise. DAAo/DDAo correlated strongly with change in vorticity (R = - 0.38, p = 0.01), helicity (R = - 0.66, p = 0.007), and WSS in the AAo (R = - 0.73, p = 0.002) and DAo (R = 0.58, p = 0.02). Estimated DAo Reynolds number negatively correlated with VO2max for exercise (R = - 0.59, p = 0.02), but not rest (R = - 0.28, p = 0.31). Visualization of streamline patterns demonstrated more secondary flow formation in aortic arches with better exercise capacity, larger DAo, and lower Reynolds number.

CONCLUSIONS: There are important associations between secondary flow characteristics and exercise capacity in repaired CoA that are not captured by traditional pressure gradient, likely due to increased turbulence and inefficient flow. These 4D flow CMR parameters are a target of investigation to identify optimal aortic arch geometry and improve long term clinical outcomes after CoA repair.}, } @article {pmid34455847, year = {2021}, author = {Simonis, S and Haussmann, M and Kronberg, L and Dörfler, W and Krause, MJ}, title = {Linear and brute force stability of orthogonal moment multiple-relaxation-time lattice Boltzmann methods applied to homogeneous isotropic turbulence.}, journal = {Philosophical transactions. Series A, Mathematical, physical, and engineering sciences}, volume = {379}, number = {2208}, pages = {20200405}, doi = {10.1098/rsta.2020.0405}, pmid = {34455847}, issn = {1471-2962}, abstract = {Multiple-relaxation-time (MRT) lattice Boltzmann methods (LBM) based on orthogonal moments exhibit lattice Mach number dependent instabilities in diffusive scaling. The present work renders an explicit formulation of stability sets for orthogonal moment MRT LBM. The stability sets are defined via the spectral radius of linearized amplification matrices of the MRT collision operator with variable relaxation frequencies. Numerical investigations are carried out for the three-dimensional Taylor-Green vortex benchmark at Reynolds number 1600. Extensive brute force computations of specific relaxation frequency ranges for the full test case are opposed to the von Neumann stability set prediction. Based on that, we prove numerically that a scan over the full wave space, including scaled mean flow variations, is required to draw conclusions on the overall stability of LBM in turbulent flow simulations. Furthermore, the von Neumann results show that a grid dependence is hardly possible to include in the notion of linear stability for LBM. Lastly, via brute force stability investigations based on empirical data from a total number of 22 696 simulations, the existence of a deterministic influence of the grid resolution is deduced. This article is part of the theme issue 'Progress in mesoscale methods for fluid dynamics simulation'.}, } @article {pmid34455509, year = {2021}, author = {Ali, A and Jana, RN and Das, S}, title = {Significance of entropy generation and heat source: the case of peristaltic blood flow through a ciliated tube conveying Cu-Ag nanoparticles using Phan-Thien-Tanner model.}, journal = {Biomechanics and modeling in mechanobiology}, volume = {20}, number = {6}, pages = {2393-2412}, pmid = {34455509}, issn = {1617-7940}, mesh = {Copper/*chemistry ; *Entropy ; *Hot Temperature ; Metal Nanoparticles/*chemistry ; *Models, Biological ; Peristalsis/*physiology ; Pressure ; Reproducibility of Results ; Silver/*chemistry ; }, abstract = {The present speculative investigation is concentrated to analyze the entropy generation and heat transfer phenomena in ciliary induced peristalsis of blood with the suspension of hybrid nanoparticles in a tube with heat source impact. The blood is assumed to contain copper (Cu) and silver (Ag) nanoparticles (NPs). The ciliary inner wall of the tube has been considered with small hair-like structures. The Phan-Thien-Tanner (PTT) fluid model is employed to describe the non-Newtonian rheological characteristics of blood. The conservative equations are normalized and simplified by utilizing scaling analysis with the assumption of low Reynolds number and large wavelength approximations. The analytical inspection exposes that the total entropy generation gets a decrement for mounting values of cilia length, while reversed impact is detected for an increment in heat source parameter. Hybrid nano-blood exhibits a greater total entropy number than mono nano-blood. This research study may be beneficial to medical experts and researchers in the field of embryology. Cysts in the ciliated fallopian tube, where embryos develop, are removed by using nanoparticles (nano-drug delivery).}, } @article {pmid34442509, year = {2021}, author = {Parveen, N and Awais, M and Awan, SE and Khan, WU and He, Y and Malik, MY}, title = {Entropy Generation Analysis and Radiated Heat Transfer in MHD (Al2O3-Cu/Water) Hybrid Nanofluid Flow.}, journal = {Micromachines}, volume = {12}, number = {8}, pages = {}, pmid = {34442509}, issn = {2072-666X}, abstract = {This research concerns the heat transfer and entropy generation analysis in the MHD axisymmetric flow of Al2O3-Cu/H2O hybrid nanofluid. The magnetic induction effect is considered for large magnetic Reynolds number. The influences of thermal radiations, viscous dissipation and convective temperature conditions over flow are studied. The problem is modeled using boundary layer theory, Maxwell's equations and Fourier's conduction law along with defined physical factors. Similarity transformations are utilized for model simplification which is analytically solved with the homotopy analysis method. The h-curves up to 20th order for solutions establishes the stability and convergence of the adopted computational method. Rheological impacts of involved parameters on flow variables and entropy generation number are demonstrated via graphs and tables. The study reveals that entropy in system of hybrid nanofluid affected by magnetic induction declines for β while it enhances for Bi, R and λ. Moreover, heat transfer rate elevates for large Bi with convective conditions at surface.}, } @article {pmid34441209, year = {2021}, author = {Ahammad, NA and Badruddin, IA and Kamangar, S and Khaleed, HMT and Saleel, CA and Mahlia, TMI}, title = {Heat Transfer and Entropy in a Vertical Porous Plate Subjected to Suction Velocity and MHD.}, journal = {Entropy (Basel, Switzerland)}, volume = {23}, number = {8}, pages = {}, pmid = {34441209}, issn = {1099-4300}, support = {RGP.1/327/42//Deanship of Scientific Research at King Khalid University/ ; }, abstract = {This article presents an investigation of heat transfer in a porous medium adjacent to a vertical plate. The porous medium is subjected to a magnetohydrodynamic effect and suction velocity. The governing equations are nondepersonalized and converted into ordinary differential equations. The resulting equations are solved with the help of the finite difference method. The impact of various parameters, such as the Prandtl number, Grashof number, permeability parameter, radiation parameter, Eckert number, viscous dissipation parameter, and magnetic parameter, on fluid flow characteristics inside the porous medium is discussed. Entropy generation in the medium is analyzed with respect to various parameters, including the Brinkman number and Reynolds number. It is noted that the velocity profile decreases in magnitude with respect to the Prandtl number, but increases with the radiation parameter. The Eckert number has a marginal effect on the velocity profile. An increased radiation effect leads to a reduced thermal gradient at the hot surface.}, } @article {pmid34432464, year = {2021}, author = {Gu, R and Lehn, JM}, title = {Constitutional Dynamic Selection at Low Reynolds Number in a Triple Dynamic System: Covalent Dynamic Adaptation Driven by Double Supramolecular Self-Assembly.}, journal = {Journal of the American Chemical Society}, volume = {143}, number = {35}, pages = {14136-14146}, doi = {10.1021/jacs.1c04446}, pmid = {34432464}, issn = {1520-5126}, abstract = {A triple dynamic complex system has been designed, implementing a dynamic covalent process coupled to two supramolecular self-assembly steps. To this end, two dynamic covalent libraries (DCLs), DCL-1 and DCL-2, have been established on the basis of dynamic covalent C═C/C═N organo-metathesis between two Knoevenagel derivatives and two imines. Each DCL contains a barbituric acid-based Knoevenagel constituent that may undergo a sequential double self-organization process involving first the formation of hydrogen-bonded hexameric supramolecular macrocycles that subsequently undergo stacking to generate a supramolecular polymer SP yielding a viscous gel state. Both DCLs display selective self-organization-driven amplification of the constituent that leads to the SP. Dissociation of the SP on heating causes reversible randomization of the constituent distributions of the DCLs as a function of temperature. Furthermore, diverse distribution patterns of DCL-2 were induced by modulation of temperature and solvent composition. The present dynamic systems display remarkable self-organization-driven constitutional adaption and tunable composition by coupling between dynamic covalent component selection and two-stage supramolecular organization. In more general terms, they reveal dynamic adaptation by component selection in low Reynolds number conditions of living systems where frictional effects dominate inertial behavior.}, } @article {pmid34410363, year = {2021}, author = {Herrera-Amaya, A and Seber, EK and Murphy, DW and Patry, WL and Knowles, TS and Bubel, MM and Maas, AE and Byron, ML}, title = {Spatiotemporal Asymmetry in Metachronal Rowing at Intermediate Reynolds Numbers.}, journal = {Integrative and comparative biology}, volume = {61}, number = {5}, pages = {1579-1593}, doi = {10.1093/icb/icab179}, pmid = {34410363}, issn = {1557-7023}, mesh = {Animals ; Biomechanical Phenomena ; Body Size ; *Extremities ; Models, Theoretical ; *Swimming ; }, abstract = {In drag-based swimming, individual propulsors operating at low Reynolds numbers (where viscous forces dominate over inertial forces) must execute a spatially asymmetric stroke to produce net fluid displacement. Temporal asymmetry (that is, differing duration between the power vs. recovery stroke) does not affect the overall generated thrust in this time-reversible regime. Metachronal rowing, in which multiple appendages beat sequentially, is used by a wide variety of organisms from low to intermediate Reynolds numbers. At the upper end of this range, inertia becomes important, and increasing temporal asymmetry can be an effective way to increase thrust. However, the combined effects of spatial and temporal asymmetry are not fully understood in the context of metachronal rowing. To explore the role of spatiotemporal asymmetry in metachronal rowing, we combine laboratory experiments and reduced-order analytical modeling. We measure beat kinematics and generated flows in two species of lobate ctenophores across a range of body sizes, from 7 to 40 mm in length. We observe characteristically different flows in ctenophores of differing body size and Reynolds number, and a general decrease in spatial asymmetry and increase in temporal asymmetry with increasing Reynolds number. We also construct a one-dimensional mathematical model consisting of a row of oscillating flat plates whose flow-normal areas change with time, and use it to explore the propulsive forces generated across a range of Reynolds numbers and kinematic parameters. The model results show that while both types of asymmetry increase force production, they have different effects in different regions of the parameter space. These results may have strong biological implications, as temporal asymmetry can be actively controlled while spatial asymmetry is likely to be partially or entirely driven by passive fluid-structure interaction.}, } @article {pmid34391375, year = {2022}, author = {Pattnaik, PK and Abbas, MA and Mishra, S and Khan, SU and Bhatti, MM}, title = {Free Convective Flow of Hamilton-Crosser Model Gold-water Nanofluid Through a Channel with Permeable Moving Walls.}, journal = {Combinatorial chemistry & high throughput screening}, volume = {25}, number = {7}, pages = {1103-1114}, doi = {10.2174/1386207324666210813112323}, pmid = {34391375}, issn = {1875-5402}, mesh = {Computer Simulation ; Gold ; Hot Temperature ; *Metal Nanoparticles ; *Water ; }, abstract = {BACKGROUND: The present manuscript analyzes the influence of buoyant forces of a conducting time-dependent nanofluid flow through porous moving walls. The medium is also filled with porous materials. In addition to that, uniform heat source and absorption parameters are considered that affect the nanofluid model.

INTRODUCTION: The model is based on the thermophysical properties of Hamilton-Crosser's nanofluid model, in which a gold nanoparticle is submerged into the base fluid water. Before simulation is obtained by a numerical method, suitable transformation is used to convert nonlinear coupled PDEs to ODEs.

METHOD: Runge-Kutta's fourth-order scheme is applied successfully for the first-order ODEs in conjunction with the shooting technique.

RESULT: Computations for the coefficients of rate constants are presented through graphs, along with the behavior of several physical parameters augmented by the flow phenomena.

CONCLUSION: The present investigation may be compatible with the applications of biotechnology. It is seen that the inclusion of volume concentration and the fluid velocity enhances near the middle layer of the channel and retards near the permeable walls. Also, augmented values of the Reynolds number and both cooling and heating of the wall increase the rate of shear stress.}, } @article {pmid34384065, year = {2021}, author = {Luo, Y and Wright, M and Xiao, Q and Yue, H and Pan, G}, title = {Fluid-structure interaction analysis on motion control of a self-propelled flexible plate near a rigid body utilizing PD control.}, journal = {Bioinspiration & biomimetics}, volume = {16}, number = {6}, pages = {}, doi = {10.1088/1748-3190/ac1cee}, pmid = {34384065}, issn = {1748-3190}, mesh = {Animals ; Biomechanical Phenomena ; Fishes ; *Models, Biological ; Motion ; *Swimming ; }, abstract = {Inspired by a previous experimental study of fish swimming near a cylinder, we numerically investigate the swimming and station-holding behavior of a flexible plate ahead of a circular cylinder whose motion is controlled by a proportional-derivative (PD) controller. Specifically, the deformation of this two-dimensional plate is actuated by a periodically varying external force applied on the body surface, which mimics the fish muscle force to produce propulsive thrust. The actuation force amplitude is dynamically adjusted by a feedback controller to instruct the plate to swim the desired distance from an initial position to a target location and then hold the station there. Instead of directly using the instantaneous position signal, an average speed measured over one force actuation period is proposed with the inclusion of instantaneous position information to form the tracking error for the PD control. Our results show that the motion control of swimming and station holding has been achieved by this simple but effective feedback control without large overshoot when approaching the target at different flow conditions and actuation force formulas. Although the swimming distance remains the same, a plate whose initial position is closer to the cylinder requires less energy expenditure to swim to the target location and hold the station there. This is because the low-pressure zone near the trailing edge of the plate is reduced in size, which provides drag reduction, contributing to reduced swimming energy. A higher Reynolds number also leads to energy savings. Under the same control strategy, the swimming performance is more affected by the force-frequency while the phase shift of the actuation force has a less significant impact.}, } @article {pmid34381068, year = {2021}, author = {Lin, P and Liu, X and Xiong, N and Wang, X and Shang, M and Liu, G and Tao, Y}, title = {Numerical study on the influence of wall temperature gradient on aerodynamic characteristics of low aspect ratio flying wing configuration.}, journal = {Scientific reports}, volume = {11}, number = {1}, pages = {16295}, pmid = {34381068}, issn = {2045-2322}, abstract = {With the aim for a low-aspect-ratio flying wing configuration, this study explores the influence of wall temperature gradient on the laminar and turbulent boundary layers of aircraft surface and determines the effect on the transition Reynolds number and wall friction drag. A four-equation turbulence model with transition mode is used to numerically simulate the flow around the model. The variation of wall friction coefficient, transition Reynolds number, and turbulent boundary layer flow with wall temperature are emphatically investigated. Results show that when the wall temperature increases from 288 to 500 K, the boundary layer transition Reynolds number for the wing section increased by approximately 28% and the surface friction drags decreases by approximately 10.7%. The hot wall enhances the viscous effects of the laminar temperature boundary layer, reduces the Reynolds shear stress and turbulent kinetic energy, and increases the flow stability. However, the velocity gradient and shear stress in the bottom of the turbulent boundary layer decreases, which leads to reduced friction shear stress on the wall surface. Therefore, for the low-aspect-ratio flying wing model, the hot wall can delay the boundary layer transition and reduce the friction drag coefficient in the turbulent region.}, } @article {pmid34373556, year = {2021}, author = {Xia, WF and Hafeez, MU and Khan, MI and Shah, NA and Chung, JD}, title = {Entropy optimized dissipative flow of hybrid nanofluid in the presence of non-linear thermal radiation and Joule heating.}, journal = {Scientific reports}, volume = {11}, number = {1}, pages = {16067}, pmid = {34373556}, issn = {2045-2322}, abstract = {Present article reads three dimensional flow analysis of incompressible viscous hybrid nanofluid in a rotating frame. Ethylene glycol is used as a base liquid while nanoparticles are of copper and silver. Fluid is bounded between two parallel surfaces in which the lower surface stretches linearly. Fluid is conducting hence uniform magnetic field is applied. Effects of non-linear thermal radiation, Joule heating and viscous dissipation are entertained. Interesting quantities namely surface drag force and Nusselt number are discussed. Rate of entropy generation is examined. Bvp4c numerical scheme is used for the solution of transformed O.D.Es. Results regarding various flow parameters are obtained via bvp4c technique in MATLAB Software version 2019, and displayed through different plots. Our obtained results presents that velocity field decreases with respect to higher values of magnetic parameter, Reynolds number and rotation parameter. It is also observed that the temperature field boots subject to radiation parameter. Results are compared with Ishak et al. (Nonlinear Anal R World Appl 10:2909-2913, 2009) and found very good agreement with them. This agreement shows that the results are 99.99% match with each other.}, } @article {pmid34373493, year = {2021}, author = {Alihosseini, Y and Azaddel, MR and Moslemi, S and Mohammadi, M and Pormohammad, A and Targhi, MZ and Heyhat, MM}, title = {Effect of liquid cooling on PCR performance with the parametric study of cross-section shapes of microchannels.}, journal = {Scientific reports}, volume = {11}, number = {1}, pages = {16072}, pmid = {34373493}, issn = {2045-2322}, abstract = {In recent years, PCR-based methods as a rapid and high accurate technique in the industry and medical fields have been expanded rapidly. Where we are faced with the COVID-19 pandemic, the necessity of a rapid diagnosis has felt more than ever. In the current interdisciplinary study, we have proposed, developed, and characterized a state-of-the-art liquid cooling design to accelerate the PCR procedure. A numerical simulation approach is utilized to evaluate 15 different cross-sections of the microchannel heat sink and select the best shape to achieve this goal. Also, crucial heat sink parameters are characterized, e.g., heat transfer coefficient, pressure drop, performance evaluation criteria, and fluid flow. The achieved result showed that the circular cross-section is the most efficient shape for the microchannel heat sink, which has a maximum heat transfer enhancement of 25% compared to the square shape at the Reynolds number of 1150. In the next phase of the study, the circular cross-section microchannel is located below the PCR device to evaluate the cooling rate of the PCR. Also, the results demonstrate that it takes 16.5 s to cool saliva samples in the PCR well, which saves up to 157.5 s for the whole amplification procedure compared to the conventional air fans. Another advantage of using the microchannel heat sink is that it takes up a little space compared to other common cooling methods.}, } @article {pmid34372345, year = {2021}, author = {Costantini, M and Henne, U and Klein, C and Miozzi, M}, title = {Skin-Friction-Based Identification of the Critical Lines in a Transonic, High Reynolds Number Flow via Temperature-Sensitive Paint.}, journal = {Sensors (Basel, Switzerland)}, volume = {21}, number = {15}, pages = {}, pmid = {34372345}, issn = {1424-8220}, abstract = {In this contribution, three methodologies based on temperature-sensitive paint (TSP) data were further developed and applied for the optical determination of the critical locations of flow separation and reattachment in compressible, high Reynolds number flows. The methodologies rely on skin-friction extraction approaches developed for low-speed flows, which were adapted in this work to study flow separation and reattachment in the presence of shock-wave/boundary-layer interaction. In a first approach, skin-friction topological maps were obtained from time-averaged surface temperature distributions, thus enabling the identification of the critical lines as converging and diverging skin-friction lines. In the other two approaches, the critical lines were identified from the maps of the propagation celerity of temperature perturbations, which were determined from time-resolved TSP data. The experiments were conducted at a freestream Mach number of 0.72 and a chord Reynolds number of 9.7 million in the Transonic Wind Tunnel Göttingen on a VA-2 supercritical airfoil model, which was equipped with two exchangeable TSP modules specifically designed for transonic, high Reynolds number tests. The separation and reattachment lines identified via the three different TSP-based approaches were shown to be in mutual agreement, and were also found to be in agreement with reference experimental and numerical data.}, } @article {pmid34359055, year = {2021}, author = {Diaz, K and Robinson, TL and Aydin, YO and Aydin, E and Goldman, DI and Wan, KY}, title = {A minimal robophysical model of quadriflagellate self-propulsion.}, journal = {Bioinspiration & biomimetics}, volume = {16}, number = {6}, pages = {}, doi = {10.1088/1748-3190/ac1b6e}, pmid = {34359055}, issn = {1748-3190}, mesh = {Flagella ; Gait ; Locomotion ; *Robotics ; *Swimming ; }, abstract = {Locomotion at the microscale is remarkably sophisticated. Microorganisms have evolved diverse strategies to move within highly viscous environments, using deformable, propulsion-generating appendages such as cilia and flagella to drive helical or undulatory motion. In single-celled algae, these appendages can be arranged in different ways around an approximately 10 μm long cell body, and coordinated in distinct temporal patterns. Inspired by the observation that some quadriflagellates (bearing four flagella) have an outwardly similar morphology and flagellar beat pattern, yet swim at different speeds, this study seeks to determine whether variations in swimming performance could arise solely from differences in swimming gait. Robotics approaches are particularly suited to such investigations, where the phase relationships between appendages can be readily manipulated. Here, we developed autonomous, algae-inspired robophysical models that can self-propel in a viscous fluid. These macroscopic robots (length and width = 8.5 cm, height = 2 cm) have four independently actuated 'flagella' (length = 13 cm) that oscillate under low-Reynolds number conditions (Re∼O(10-1)). We tested the swimming performance of these robot models with appendages arranged two distinct configurations, and coordinated in three distinct gaits. The gaits, namely the pronk, the trot, and the gallop, correspond to gaits adopted by distinct microalgal species. When the appendages are inserted perpendicularly around a central 'body', the robot achieved a net performance of 0.15-0.63 body lengths per cycle, with the trot gait being the fastest. Robotic swimming performance was found to be comparable to that of the algal microswimmers across all gaits. By creating a minimal robot that can successfully reproduce cilia-inspired drag-based swimming, our work paves the way for the design of next-generation devices that have the capacity to autonomously navigate aqueous environments.}, } @article {pmid34357216, year = {2021}, author = {Li, L and Chen, Q and Sui, G and Qian, J and Tsai, CT and Cheng, X and Jing, W}, title = {A Three-Dimensional Micromixer Using Oblique Embedded Ridges.}, journal = {Micromachines}, volume = {12}, number = {7}, pages = {}, pmid = {34357216}, issn = {2072-666X}, abstract = {A micromixer is one of the most significant components in a microfluidic system. A three-dimensional micromixer was developed with advantages of high efficiency, simple fabrication, easy integration, and ease of mass production. The designed principle is based on the concepts of splitting-recombination and chaotic advection. A numerical model of this micromixer was established to characterize the mixing performance for different parameters. A critical Reynolds number (Re) was obtained from the simulation results. When the Re number is smaller than the critical value, the fluid mixing is mainly dependent on the mechanism of splitting-recombination, therefore, the length of the channel capable of complete mixing (complete mixing length) increases as the Re number increases. When the Re number is larger than the critical value, the fluid mixing is dominated by chaotic advection, and the complete mixing length decreases as the Re number increases. For normal fluids, a complete mixing length of 500 µm can be achieved at a very small Re number of 0.007 and increases to 2400 µm as the Re number increases to the critical value of 4.7. As the Re number keep increasing and passes the critical Re number, the complete mixing length continues to descend to 650 µm at the Re number of 66.7. For hard-to-mix fluids (generally referring to fluids with high viscosity and low diffusion coefficient, which are difficult to mix), even though no evidence of strong chaotic advection is presented in the simulation, the micromixer can still achieve a complete mixing length of 2550 µm. The mixing performance of the micromixer was also verified by experiments. The experimental results showed a consistent trend with the numerical simulation results, which both climb upward when the Re number is around 0.007 (flow rate of 0.03 μm/min) to around 10 (flow rate of 50 μm/min), then descend when the Re number is around 13.3 (flow rate of 60 µm/min).}, } @article {pmid34357184, year = {2021}, author = {Nichka, VS and Nikonenko, VV and Bazinet, L}, title = {Fouling Mitigation by Optimizing Flow Rate and Pulsed Electric Field during Bipolar Membrane Electroacidification of Caseinate Solution.}, journal = {Membranes}, volume = {11}, number = {7}, pages = {}, pmid = {34357184}, issn = {2077-0375}, support = {19-38-90256//Russian Foundation for Basic Research/ ; 210829409//Natural Sciences and Engineering Research Council of Canada/ ; }, abstract = {The efficiency of separation processes using ion exchange membranes (IEMs), especially in the food industry, is significantly limited by the fouling phenomenon, which is the process of the attachment and growth of certain species on the surface and inside the membrane. Pulsed electric field (PEF) mode, which consists in the application of constant current density pulses during a fixed time (Ton) alternated with pause lapses (Toff), has a positive antifouling impact. The aim of this study was to investigate the combined effect of three different relatively high flow rates of feed solution (corresponding to Reynolds numbers of 187, 374 and 560) and various pulse-pause ratios of PEF current regime on protein fouling kinetics during electrodialysis with bipolar membranes (EDBM) of a model caseinate solution. Four different pulse/pause regimes (with Ton/Toff ratios equal to 10 s/10 s, 10 s/20 s, 10 s/33 s and 10 s/50 s) during electrodialysis (ED) treatment were evaluated at a current density of 5 mA/cm2. It was found that increasing the pause duration and caseinate solution flow rate had a positive impact on the minimization of protein fouling occurring on the cationic surface of the bipolar membrane (BPM) during the EDBM. Both a long pause and high flow rate contribute to a more effective decrease in the concentration of protons and caseinate anions at the BPM surface: a very good membrane performance was achieved with 50 s of pause duration of PEF and a flow rate corresponding to Re = 374. A further increase in PEF pause duration (above 50 s) or flow rate (above Re = 374) did not lead to a significant decrease in the amount of fouling.}, } @article {pmid34349343, year = {2021}, author = {Ferroni, C and Bracconi, M and Ambrosetti, M and Maestri, M and Groppi, G and Tronconi, E}, title = {A Fundamental Investigation of Gas/Solid Heat and Mass Transfer in Structured Catalysts Based on Periodic Open Cellular Structures (POCS).}, journal = {Industrial & engineering chemistry research}, volume = {60}, number = {29}, pages = {10522-10538}, pmid = {34349343}, issn = {0888-5885}, abstract = {In this work, we investigate the gas-solid heat and mass transfer in catalytically activated periodic open cellular structures, which are considered a promising solution for intensification of catalytic processes limited by external transport, aiming at the derivation of suitable correlations. Computational fluid dynamics is employed to investigate the Tetrakaidekahedral and Diamond lattice structures. The influence of the morphological features and flow conditions on the external transport properties is assessed. The strut diameter is an adequate characteristic length for the formulation of heat and mass transfer correlations; accordingly, a power-law dependence of the Sherwood number to the Reynolds number between 0.33 and 0.67 was found according to the flow regimes in the range 1-128 of the Reynolds number. An additional -1.5-order dependence on the porosity is found. The formulated correlations are in good agreement with the simulation results and allow for the accurate evaluation of the external transfer coefficients for POCS.}, } @article {pmid34335006, year = {2021}, author = {Liu, K and Allahyari, M and Salinas, J and Zgheib, N and Balachandar, S}, title = {Investigation of theoretical scaling laws using large eddy simulations for airborne spreading of viral contagion from sneezing and coughing.}, journal = {Physics of fluids (Woodbury, N.Y. : 1994)}, volume = {33}, number = {6}, pages = {063318}, pmid = {34335006}, issn = {1070-6631}, abstract = {Using a set of large eddy point-particle simulations, we explore the fluid dynamics of an ejected puff resulting from a cough/sneeze. The ejection contains over 61 000 potentially virus-laden droplets at an injection Reynolds number of about 46 000, comparable to an actual cough/sneeze. We observe that global puff properties, such as centroid, puff volume, momentum, and buoyancy vary little across realizations. Other properties, such as maximum extent, shape, and edge velocity of the puff, may exhibit substantial variation. In many realizations, a portion of the puff splits off and advances along a random direction, while keeping airborne droplet nuclei afloat. This peeled-off portion provides a mechanism for virus-laden droplets to travel over large distances in a short amount of time. We also observe that the vast majority of droplets remain suspended within the puff after all liquid has evaporated. The main objectives of the study are to (i) evaluate assumptions of Balachandar's et al. theory [Int. J. Multiphase Flow 132, 103439 (2020)], which include buoyancy effects, shape of the puff, and droplet evaporation rate, (ii) obtain values of closure parameters, which include location and time of the virtual origin, and puff entrainment and drag coefficients, and (iii) evaluate the accuracy of the theory in predicting the shape, size, and location of the puff, as well as droplet number density long after ejection. The theory adequately predicts global puff properties including size, velocity, and distance traveled, the largest size of droplets that exit the puff due to settling, and the droplet size distribution within the puff long after ejection.}, } @article {pmid34319753, year = {2021}, author = {Singh, RK and Mahato, LK and Mandal, DK}, title = {Airflow-Assisted Impact of Drops of Various Viscosities: The Role of Viscous Dissipation, Normal Imposed Pressure, and Shear Flow of Air.}, journal = {Langmuir : the ACS journal of surfaces and colloids}, volume = {37}, number = {31}, pages = {9504-9517}, doi = {10.1021/acs.langmuir.1c01367}, pmid = {34319753}, issn = {1520-5827}, abstract = {The role of liquid viscosity on the spreading for an airflow-assisted impact of drops on a surface is investigated. The spreading diameter is found to increase with the Reynolds number of the airflow (Reair) for a given viscosity and impact Weber number (We) compared to the still air. The increment is higher at a low We for viscous drops, whereas the effect of Reair dominates at the intermediate We as the viscosity decreases. Two extra forces, the normal imposed pressure and shear force of air, act on the drop and influence the spreading along with the viscous dissipation. The drop's curvature decreases depending on the viscosity and impact velocity while spreading. Large-scale eddies near the drop-surface region are observed due to the separation of the incident airflow. The formation of eddies signifies low-pressure zones, which extract the trapped air, causing the spreading diameter of the viscous drop to increase at a low We. With the increase in the We, the lamella thickness of low-viscosity drops decreases and is pushed out by the air shear causing the spreading factor to increase. The boundary layer thickness is estimated using the energy balance method to predict the maximum spreading factor. The prediction compares well with the experimental one for higher viscosities. The accuracy improves when the effect of low pressure is incorporated. To confirm, the experimental spreading is compared with that obtained from three existing models, and one, which considers the influence, is observed to provide a better prediction.}, } @article {pmid34297252, year = {2021}, author = {Sharifi, A and Gendernalik, A and Garrity, D and Bark, D}, title = {Valveless pumping behavior of the simulated embryonic heart tube as a function of contractile patterns and myocardial stiffness.}, journal = {Biomechanics and modeling in mechanobiology}, volume = {20}, number = {5}, pages = {2001-2012}, pmid = {34297252}, issn = {1617-7940}, mesh = {Animals ; Biomechanical Phenomena ; Cardiac Output ; Computer Simulation ; Electric Impedance ; Heart/*embryology/*physiology ; Heart Rate ; *Hemodynamics ; Models, Cardiovascular ; Models, Theoretical ; *Myocardial Contraction ; Myocardium/*pathology ; Peristalsis ; Pressure ; Stress, Mechanical ; Zebrafish/*embryology ; }, abstract = {During development, the heart begins pumping as a valveless multilayered tube capable of driving blood flow throughout the embryonic vasculature. The mechanical properties and how they interface with pumping function are not well-defined at this stage. Here, we evaluate pumping patterns using a fluid-structure interaction computational model, combined with experimental data and an energetic analysis to investigate myocardial mechanical properties. Through this work, we propose that a myocardium modeled as a Neo-Hookean material with a material constant on the order of 10 kPa is necessary for the heart tube to function with an optimal pressure and cardiac output.}, } @article {pmid34293964, year = {2021}, author = {Akram, S and Athar, M and Saeed, K and Razia, A}, title = {Crossbreed impact of double-diffusivity convection on peristaltic pumping of magneto Sisko nanofluids in non-uniform inclined channel: A bio-nanoengineering model.}, journal = {Science progress}, volume = {104}, number = {3}, pages = {368504211033677}, doi = {10.1177/00368504211033677}, pmid = {34293964}, issn = {2047-7163}, abstract = {The consequences of double-diffusivity convection on the peristaltic transport of Sisko nanofluids in the non-uniform inclined channel and induced magnetic field are discussed in this article. The mathematical modeling of Sisko nanofluids with induced magnetic field and double-diffusivity convection is given. To simplify PDEs that are highly nonlinear in nature, the low but finite Reynolds number, and long wavelength estimation are used. The Numerical solution is calculated for the non-linear PDEs. The exact solution of concentration, temperature and nanoparticle are obtained. The effect of various physical parameters of flow quantities is shown in numerical and graphical data. The outcomes show that as the thermophoresis and Dufour parameters are raised, the profiles of temperature, concentration, and nanoparticle fraction all significantly increase.}, } @article {pmid34286832, year = {2021}, author = {Kasoju, VT and Moen, DS and Ford, MP and Ngo, TT and Santhanakrishnan, A}, title = {Interspecific variation in bristle number on forewings of tiny insects does not influence clap-and-fling aerodynamics.}, journal = {The Journal of experimental biology}, volume = {224}, number = {18}, pages = {}, doi = {10.1242/jeb.239798}, pmid = {34286832}, issn = {1477-9145}, mesh = {Animals ; Biomechanical Phenomena ; *Flight, Animal ; Insecta ; Models, Biological ; Phylogeny ; *Wings, Animal ; }, abstract = {Miniature insects must overcome significant viscous resistance in order to fly. They typically possess wings with long bristles on the fringes and use a clap-and-fling mechanism to augment lift. These unique solutions to the extreme conditions of flight at tiny sizes (<2 mm body length) suggest that natural selection has optimized wing design for better aerodynamic performance. However, species vary in wingspan, number of bristles (n) and bristle gap (G) to diameter (D) ratio (G/D). How this variation relates to body length (BL) and its effects on aerodynamics remain unknown. We measured forewing images of 38 species of thrips and 21 species of fairyflies. Our phylogenetic comparative analyses showed that n and wingspan scaled positively and similarly with BL across both groups, whereas G/D decreased with BL, with a sharper decline in thrips. We next measured aerodynamic forces and visualized flow on physical models of bristled wings performing clap-and-fling kinematics at a chord-based Reynolds number of 10 using a dynamically scaled robotic platform. We examined the effects of dimensional (G, D, wingspan) and non-dimensional (n, G/D) geometric variables on dimensionless lift and drag. We found that: (1) increasing G reduced drag more than decreasing D; (2) changing n had minimal impact on lift generation; and (3) varying G/D minimally affected aerodynamic forces. These aerodynamic results suggest little pressure to functionally optimize n and G/D. Combined with the scaling relationships between wing variables and BL, much wing variation in tiny flying insects might be best explained by underlying shared growth factors.}, } @article {pmid34283850, year = {2021}, author = {Dvoriashyna, M and Lauga, E}, title = {Hydrodynamics and direction change of tumbling bacteria.}, journal = {PloS one}, volume = {16}, number = {7}, pages = {e0254551}, pmid = {34283850}, issn = {1932-6203}, mesh = {Biomechanical Phenomena ; Escherichia coli/chemistry/*physiology ; Flagella/*physiology ; *Hydrodynamics ; Models, Biological ; Movement/*physiology ; Rotation ; Swimming/physiology ; }, abstract = {The bacterium Escherichia coli (E. coli) swims in viscous fluids by rotating several helical flagellar filaments, which are gathered in a bundle behind the cell during 'runs' wherein the cell moves steadily forward. In between runs, the cell undergoes quick 'tumble' events, during which at least one flagellum reverses its rotation direction and separates from the bundle, resulting in erratic motion in place and a random reorientation of the cell. Alternating between runs and tumbles allows cells to sample space by stochastically changing their propulsion direction after each tumble. The change of direction during a tumble is not uniformly distributed but is skewed towards smaller angles with an average of about 62°-68°, as first measured by Berg and Brown (1972). Here we develop a theoretical approach to model the angular distribution of swimming E. coli cells during tumbles. We first use past experimental imaging results to construct a kinematic description of the dynamics of the flagellar filaments during a tumble. We then employ low-Reynolds number hydrodynamics to compute the consequences of the kinematic model on the force and torque balance of the cell and to deduce the overall change in orientation. The results of our model are in good agreement with experimental observations. We find that the main change of direction occurs during the 'bundling' part of the process wherein, at the end of a tumble, the dispersed flagellar filaments are brought back together in the helical bundle, which we confirm using a simplified forced-sphere model.}, } @article {pmid34282226, year = {2021}, author = {Ishak, MS and Alsabery, AI and Hashim, I and Chamkha, AJ}, title = {Entropy production and mixed convection within trapezoidal cavity having nanofluids and localised solid cylinder.}, journal = {Scientific reports}, volume = {11}, number = {1}, pages = {14700}, pmid = {34282226}, issn = {2045-2322}, support = {FRGS/1/2019/STG06/UKM/01/2//Malaysian Ministry of Education/ ; FRGS/1/2019/STG06/UKM/01/2//Malaysian Ministry of Education/ ; }, abstract = {The entropy production and mixed convection within a trapezoidal nanofluid-filled cavity having a localised solid cylinder is numerically examined using the finite element technique. The top horizontal surface moving at a uniform velocity is kept at a cold temperature, while the bottom horizontal surface is thermally activated. The remaining surfaces are maintained adiabatic. Water-based nanofluids ([Formula: see text] nanoparticles) are used in this study, and the Boussinesq approximation applies. The influence of the Reynolds number, Richardson number, nanoparticles volume fraction, dimensionless radius and location of the solid cylinder on the streamlines, isotherms and isentropic are examined. The results show that the solid cylinder's size and location are significant control parameters for optimising the heat transfer and the Bejan number inside the trapezoidal cavity. Furthermore, the maximum average Nusselt numbers are obtained for high R values, where the average Nusselt number is increased by 30% when R is raised from 0 to 0.25.}, } @article {pmid34275183, year = {2021}, author = {Gurovich, AN and Rodriguez, L and Morales-Acuna, F}, title = {There are no differences in brachial artery endothelial shear stress and blood flow patterns between males and females during exercise.}, journal = {Clinical physiology and functional imaging}, volume = {41}, number = {6}, pages = {471-479}, doi = {10.1111/cpf.12722}, pmid = {34275183}, issn = {1475-097X}, mesh = {*Brachial Artery/diagnostic imaging ; Cross-Sectional Studies ; *Endothelium, Vascular ; Exercise ; Female ; Hemodynamics ; Humans ; Male ; Regional Blood Flow ; Vasodilation ; }, abstract = {Premenopausal females have a lower cardiovascular risk than males. Sex differences on exercise-induced endothelial shear stress (ESS) and blood flow patterns may explain part of this risk reduction. The purpose of this cross-sectional study was to determine the differences in brachial artery exercise-induced ESS and blood flow patterns between males and females. Thirty subjects (13 females) were recruited to perform a three-workload steady-state exercise test based on blood lactate levels (i.e. <2.0, 2.0-4.0, >4.0 mmol/l). ESS and blood flow patterns were estimated at rest and during each workload using Womersley's approximation and Reynolds number, respectively. Both males and females showed an exercise intensity-dependent increase in antegrade and retrograde ESS. There was no significant sex effect or interaction for antegrade ESS (F(1, 30) = 0.715, p = 0.405 and F(1·672, 60) = 1.511, p = 0.232, respectively) or retrograde ESS (F(1, 30) = 0.794, p = 0.380 and F(1·810, 60) = 1.022, p = 0.361, respectively). Additionally, antegrade blood flow was turbulent during all bouts of exercise while retrograde blood flow became disturbed at moderate and high exercise intensities in both groups. There are no differences in exercise-induced ESS and blood flow patterns between males and females when the exercise load is equivalent. This suggests that the vascular benefits of exercise training are similar in both sexes from a haemodynamic standpoint.}, } @article {pmid34272432, year = {2021}, author = {Gul, H and Ramzan, M and Chung, JD and Chu, YM and Kadry, S}, title = {Multiple slips impact in the MHD hybrid nanofluid flow with Cattaneo-Christov heat flux and autocatalytic chemical reaction.}, journal = {Scientific reports}, volume = {11}, number = {1}, pages = {14625}, pmid = {34272432}, issn = {2045-2322}, support = {20202020900060//Korea Institute of Energy Technology Evaluation and Planning/ ; }, abstract = {The present study deliberates the nanofluid flow containing multi and single-walled carbon nanotubes submerged into Ethylene glycol in a Darcy-Forchheimer permeable media over a stretching cylinder with multiple slips. The innovation of the envisaged mathematical model is enriched by considering the impacts of non-uniform source/sink and modified Fourier law in the energy equation and autocatalytic chemical reaction in the concentration equation. Entropy optimization analysis of the mathematical model is also performed in the present problem. Pertinent transformations procedure is implemented for the conversion of the non-linear system to the ordinary differential equations. The succor of the Shooting technique combined with the bvp4c MATLAB software is utilized for the solution of a highly nonlinear system of equations. The impacts of the leading parameters versus engaged fields are inspected through graphical sketches. The outcomes show that a strong magnetic field strengthens the temperature profile and decays the velocity profile. Also, the fluid velocity is lessened for growing estimates of the parameter of slip. Additionally, it is detected that entropy number augmented for higher thermal relaxation parameter and Reynolds number. To substantiate the existing mathematical model, a comparison table is also added. An excellent correlation is achieved here.}, } @article {pmid34272408, year = {2021}, author = {Wang, H and Enders, A and Preuss, JA and Bahnemann, J and Heisterkamp, A and Torres-Mapa, ML}, title = {3D printed microfluidic lab-on-a-chip device for fiber-based dual beam optical manipulation.}, journal = {Scientific reports}, volume = {11}, number = {1}, pages = {14584}, pmid = {34272408}, issn = {2045-2322}, abstract = {3D printing of microfluidic lab-on-a-chip devices enables rapid prototyping of robust and complex structures. In this work, we designed and fabricated a 3D printed lab-on-a-chip device for fiber-based dual beam optical manipulation. The final 3D printed chip offers three key features, such as (1) an optimized fiber channel design for precise alignment of optical fibers, (2) an optically clear window to visualize the trapping region, and (3) a sample channel which facilitates hydrodynamic focusing of samples. A square zig-zag structure incorporated in the sample channel increases the number of particles at the trapping site and focuses the cells and particles during experiments when operating the chip at low Reynolds number. To evaluate the performance of the device for optical manipulation, we implemented on-chip, fiber-based optical trapping of different-sized microscopic particles and performed trap stiffness measurements. In addition, optical stretching of MCF-7 cells was successfully accomplished for the purpose of studying the effects of a cytochalasin metabolite, pyrichalasin H, on cell elasticity. We observed distinct changes in the deformability of single cells treated with pyrichalasin H compared to untreated cells. These results demonstrate that 3D printed microfluidic lab-on-a-chip devices offer a cost-effective and customizable platform for applications in optical manipulation.}, } @article {pmid34271062, year = {2021}, author = {Dubey, A and B, V and Bég, OA and Gorla, RSR}, title = {Finite element computation of magneto-hemodynamic flow and heat transfer in a bifurcated artery with saccular aneurysm using the Carreau-Yasuda biorheological model.}, journal = {Microvascular research}, volume = {138}, number = {}, pages = {104221}, doi = {10.1016/j.mvr.2021.104221}, pmid = {34271062}, issn = {1095-9319}, mesh = {Aorta/*physiopathology ; Aortic Aneurysm/*physiopathology ; Blood Flow Velocity ; Computer Simulation ; Electric Conductivity ; Energy Transfer ; Finite Element Analysis ; *Hemorheology ; Hot Temperature ; Humans ; *Magnetic Fields ; *Models, Cardiovascular ; Pulsatile Flow ; Regional Blood Flow ; Stress, Mechanical ; Time Factors ; }, abstract = {"Existing computational fluid dynamics studies of blood flows have demonstrated that the lower wall stress and higher oscillatory shear index might be the cause of acceleration in atherogenesis of vascular walls in hemodynamics. To prevent the chances of aneurysm wall rupture in the saccular aneurysm at distal aortic bifurcation, clinical biomagnetic studies have shown that extra-corporeal magnetic fields can be deployed to regulate the blood flow. Motivated by these developments, in the current study a finite element computational fluid dynamics simulation has been conducted of unsteady two-dimensional non-Newtonian magneto-hemodynamic heat transfer in electrically conducting blood flow in a bifurcated artery featuring a saccular aneurysm. The fluid flow is assumed to be pulsatile, non-Newtonian and incompressible. The Carreau-Yasuda model is adopted for blood to mimic non-Newtonian characteristics. The transformed equations with appropriate boundary conditions are solved numerically by employing the finite element method with the variational approach in the FreeFEM++ code. Hydrodynamic and thermal characteristics are elucidated in detail for the effects of key non-dimensional parameters i.e. Reynolds number (Re = 14, 21, 100, 200), Prandtl number (Pr = 14, 21) and magnetic body force parameter (Hartmann number) (M = 0.6, 1.2, 1.5) at the aneurysm and throughout the arterial domain. The influence of vessel geometry on blood flow characteristics i.e. velocity, pressure and temperature fields are also visualized through instantaneous contour patterns. It is found that an increase in the magnetic parameter reduces the pressure but increases the skin-friction coefficient in the domain. The temperature decreases at the parent artery (inlet) and both the distant and prior artery with the increment in the Prandtl number. A higher Reynolds number also causes a reduction in velocity as well as in pressure. The blood flow shows different characteristic contours with time variation at the aneurysm as well as in the arterial segment. The novelty of the current research is therefore to present a combined approach amalgamating the Carreau-Yasuda model, heat transfer and magnetohydrodynamics with complex geometric features in realistic arterial hemodynamics with extensive visualization and interpretation, in order to generalize and extend previous studies. In previous studies these features have been considered separately and not simultaneously as in the current study. The present simulations reveal some novel features of biomagnetic hemodynamics in bifurcated arterial transport featuring a saccular aneurysm which are envisaged to be of relevance in furnishing improved characterization of the rheological biomagnetic hemodynamics of realistic aneurysmic bifurcations in clinical assessment, diagnosis and magnetic-assisted treatment of cardiovascular disease."}, } @article {pmid34266946, year = {2021}, author = {Han, E and Zhu, L and Shaevitz, JW and Stone, HA}, title = {Low-Reynolds-number, biflagellated Quincke swimmers with multiple forms of motion.}, journal = {Proceedings of the National Academy of Sciences of the United States of America}, volume = {118}, number = {29}, pages = {}, pmid = {34266946}, issn = {1091-6490}, mesh = {Hydrodynamics ; Locomotion/*physiology ; *Models, Biological ; Motion ; Rheology ; Rotation ; }, abstract = {In the limit of zero Reynolds number (Re), swimmers propel themselves exploiting a series of nonreciprocal body motions. For an artificial swimmer, a proper selection of the power source is required to drive its motion, in cooperation with its geometric and mechanical properties. Although various external fields (magnetic, acoustic, optical, etc.) have been introduced, electric fields are rarely utilized to actuate such swimmers experimentally in unbounded space. Here we use uniform and static electric fields to demonstrate locomotion of a biflagellated sphere at low Re via Quincke rotation. These Quincke swimmers exhibit three different forms of motion, including a self-oscillatory state due to elastohydrodynamic-electrohydrodynamic interactions. Each form of motion follows a distinct trajectory in space. Our experiments and numerical results demonstrate a method to generate, and potentially control, the locomotion of artificial flagellated swimmers.}, } @article {pmid34260387, year = {2021}, author = {Zhang, B and Leishangthem, P and Ding, Y and Xu, X}, title = {An effective and efficient model of the near-field hydrodynamic interactions for active suspensions of bacteria.}, journal = {Proceedings of the National Academy of Sciences of the United States of America}, volume = {118}, number = {28}, pages = {}, pmid = {34260387}, issn = {1091-6490}, mesh = {Computer Simulation ; Escherichia coli/*physiology ; *Hydrodynamics ; *Models, Biological ; Suspensions ; }, abstract = {Near-field hydrodynamic interactions in active fluids are essential to determine many important emergent behaviors observed, but have not been successfully modeled so far. In this work, we propose an effective model capturing the essence of the near-field hydrodynamic interactions through a tensorial coefficient of resistance, validated numerically by a pedagogic model system consisting of an Escherichia coli bacterium and a passive sphere. In a critical test case that studies the scattering angle of the bacterium-sphere pair dynamics, we prove that the near-field hydrodynamics can make a qualitative difference even for this simple two-body system: Calculations based on the proposed model reveal a region in parameter space where the bacterium is trapped by the passive sphere, a phenomenon that is regularly observed in experiments but cannot be explained by any existing model. In the end, we demonstrate that our model also leads to efficient simulation of active fluids with tens of thousands of bacteria, sufficiently large for investigations of many emergent behaviors.}, } @article {pmid34251258, year = {2021}, author = {Charakopoulos, A and Karakasidis, T and Sarris, I}, title = {Analysis of magnetohydrodynamic channel flow through complex network analysis.}, journal = {Chaos (Woodbury, N.Y.)}, volume = {31}, number = {4}, pages = {043123}, doi = {10.1063/5.0043817}, pmid = {34251258}, issn = {1089-7682}, abstract = {Velocity time series of hydrodynamic and magnetohydrodynamic (MHD) turbulent flow are analyzed by means of complex network analysis in order to understand the mechanism of fluid patterns modification due to the external magnetic field. Direct numerical simulations of two cases are used, one for the plane hydrodynamic turbulent channel flow at the low Reynolds number of 180, based on the friction velocity, and the corresponding MHD flow with an external streamwise magnetic field with a magnetic interaction number of 0.1. By applying the visibility graph algorithm, we first transformed the time series into networks and then we evaluated the network topological properties. Results show that the proposed network analysis is not only able to identify and detect dynamical transitions in the system's behavior that identifies three distinct fluid areas in accordance with turbulent flow theory but also can quantify the effect of the magnetic field on the time series transitions. Moreover, we find that the topological measures of networks without a magnetic field and as compared to the one with a magnetic field are statistically different within a 95% confidence interval. These results provide a way to discriminate and characterize the influence of the magnetic field on the turbulent flows.}, } @article {pmid34247118, year = {2021}, author = {Tang, TQ and Hsu, SY and Dahiya, A and Soh, CH and Lin, KC}, title = {Numerical modeling of pulsatile blood flow through a mini-oxygenator in artificial lungs.}, journal = {Computer methods and programs in biomedicine}, volume = {208}, number = {}, pages = {106241}, doi = {10.1016/j.cmpb.2021.106241}, pmid = {34247118}, issn = {1872-7565}, mesh = {Equipment Design ; Humans ; Hydrodynamics ; Lung ; *Oxygen ; *Oxygenators, Membrane ; Pulsatile Flow ; }, abstract = {While previous in vitro studies showed divergent results concerning the influence of pulsatile blood flow on oxygen advection in oxygenators, no study was done to investigate the uncertainty affected by blood flow dynamics. The aim of this study is to utilize a computational fluid dynamics model to clarify the debate concerning the influence of pulsatile blood flow on the oxygen transport. The computer model is based on a validated 2D finite volume approach that predicts oxygen transfer in pulsatile blood flow passing through a 300-micron hollow-fiber membrane bundle with a length of 254 mm, a building block for an artificial lung device. In this study, the flow parameters include the steady Reynolds number (Re = 2, 5, 10 and 20), Womersley parameter (Wo = 0.29, 0.38 and 0.53) and sinusoidal amplitude (A = 0.25, 0.5 and 0.75). Specifically, the computer model is extended to verify, for the first time, the previously measured O2 transport that was observed to be hindered by pulsating flow in the Biolung, developed by Michigan Critical Care Consultants. A comprehensive analysis is carried out on computed profiles and fields of oxygen partial pressure (PO2) and oxygen saturation (SO2) as a function of Re, Wo and A. Based on the present results, we observe the positive and negative effects of pulsatile flow on PO2 at different blood flow rates. Besides, the SO2 variation is not much influenced by the pulsatile flow conditions investigated. While being consistent with a recent experimental study, the computed O2 volume flow rate is found to be increased at high blood flow rates operated with low frequency and high amplitude. Furthermore, the present study qualitatively explains that divergent outcomes reported in previous in vitro experimental studies could be owing to the different blood flow rates adopted. Finally, the contour analysis reveals how the spatial distributions of PO2 and SO2 vary over time.}, } @article {pmid34243174, year = {2021}, author = {Meng, X and Ghaffar, A and Zhang, Y and Deng, C}, title = {Very low Reynolds number causes a monotonic force enhancement trend for a three-dimensional hovering wing in ground effect.}, journal = {Bioinspiration & biomimetics}, volume = {16}, number = {5}, pages = {}, doi = {10.1088/1748-3190/ac1308}, pmid = {34243174}, issn = {1748-3190}, mesh = {Animals ; Biomechanical Phenomena ; *Flight, Animal ; Insecta ; Models, Biological ; *Wings, Animal ; }, abstract = {This research reports the numerical results of the ground effect trend for a three-dimensional flapping insect wing at a very low Reynolds number (Re = 10). It demonstrates that the ground effect trend at this Re has a 'single force regime,' i.e. the forces only enhance as the ground distance decreases. This phenomenon is unlike the widely expected non-monotonic trend publicized in previous studies for higher Reynolds numbers, that shows 'three force regimes,' i.e. the forces reduce, recover, and also enhance as the ground distance decreases. The force trend in the ground effect correlates to a similar trend in wing-wake interaction or the downwash strength on the wing's head. At very low Re (10), the very large viscosity causes diffused vortices and less advected vortex wake, while at relatively high Re, the vortices are easily separated from the wing and then advected downwards. This different development of the vortex wake caused different force trends for the flapping wing in the ground effect. Furthermore, by examining only the first stroke when there is no vortex wake, we found that the 'ramming effect' enhances the forces on the wing. This effect increases the pressure of the lower wing surface due to the squeezed air between the wing and the ground. The 'ramming effect', combined with the reduced downwash (or wing-wake interaction) effect, causes the force enhancement of the wing near the ground's vicinity. It is further comprehended that the trend is dependent on Re. As the Re is increased, the trend becomes non-monotonic. The effect of varying angles of attack, flapping amplitude and wing planform at very low Re does not change this trend. This ground effect might help insects by enhancing their lift while they hover above the surface. This finding might prove beneficial for developing micro air vehicles.}, } @article {pmid34241532, year = {2021}, author = {Iyer, KP and Bewley, GP and Biferale, L and Sreenivasan, KR and Yeung, PK}, title = {Oscillations Modulating Power Law Exponents in Isotropic Turbulence: Comparison of Experiments with Simulations.}, journal = {Physical review letters}, volume = {126}, number = {25}, pages = {254501}, doi = {10.1103/PhysRevLett.126.254501}, pmid = {34241532}, issn = {1079-7114}, abstract = {Inertial-range features of turbulence are investigated using data from experimental measurements of grid turbulence and direct numerical simulations of isotropic turbulence simulated in a periodic box, both at the Taylor-scale Reynolds number R_{λ} ∼1000. In particular, oscillations modulating the power-law scaling in the inertial range are examined for structure functions up to sixth-order moments. The oscillations in exponent ratios decrease with increasing sample size in simulations, although in experiments they survive at a low value of 4 parts in 1000 even after massive averaging. The two datasets are consistent in their intermittent character but differ in small but observable respects. Neither the scaling exponents themselves nor all the viscous effects are consistently reproduced by existing models of intermittency.}, } @article {pmid34241478, year = {2021}, author = {Gojon, R and Jardin, T and Parisot-Dupuis, H}, title = {Experimental investigation of low Reynolds number rotor noise.}, journal = {The Journal of the Acoustical Society of America}, volume = {149}, number = {6}, pages = {3813}, doi = {10.1121/10.0005068}, pmid = {34241478}, issn = {1520-8524}, abstract = {In this paper, an experimental characterisation of low Reynolds number rotors is performed in an anechoic room. Two commercially available two-bladed rotors as well as four three-dimensional (3D)-printed rotors with different numbers of blades (from two to five) are tested. The latter have canonical geometry, with an NACA0012 blade section profile, extruded in the radial direction with constant chord and constant 10° pitch. The experimental setup and the 3D printing strategy are first validated using results from the literature for the commercially available rotors. For all the tested rotors, four noise characteristics are analysed: the overall sound pressure level (OASPL), the amplitude of the blade passing frequency (BPF), and the amplitude of its first harmonic and the high-frequency broadband noise. For all the rotors, an increase in all noise characteristics is observed with the rotational speed (rpm) for all directivity angles. Moreover, an interesting change of pattern is observed for the amplitudes of the BPF and of its first harmonic, with, in the vicinity of the rotor plane, a minimum value for low rpm and/or high number of blades, and a maximum value for high rpm and/or low number of blades. This change in directivity leads to a similar change of directivity of the OASPL. For the broadband noise, a dipole-like pattern is obtained with a minimum value at θ=-10°, i.e., aligned with the trailing edge and thus indicating the generation of trailing edge noise. Finally, scaling laws that characterise the amplitude of the different noise components with respect to the rpm are proposed.}, } @article {pmid34234957, year = {2021}, author = {Mazharmanesh, S and Stallard, J and Medina, A and Fisher, A and Ando, N and Tian, FB and Young, J and Ravi, S}, title = {Effects of uniform vertical inflow perturbations on the performance of flapping wings.}, journal = {Royal Society open science}, volume = {8}, number = {6}, pages = {210471}, pmid = {34234957}, issn = {2054-5703}, abstract = {Flapping wings have attracted significant interest for use in miniature unmanned flying vehicles. Although numerous studies have investigated the performance of flapping wings under quiescent conditions, effects of freestream disturbances on their performance remain under-explored. In this study, we experimentally investigated the effects of uniform vertical inflows on flapping wings using a Reynolds-scaled apparatus operating in water at Reynolds number ≈ 3600. The overall lift and drag produced by a flapping wing were measured by varying the magnitude of inflow perturbation from J Vert = -1 (downward inflow) to J Vert = 1 (upward inflow), where J Vert is the ratio of the inflow velocity to the wing's velocity. The interaction between flapping wing and downward-oriented inflows resulted in a steady linear reduction in mean lift and drag coefficients, C ¯ L and C ¯ D , with increasing inflow magnitude. While a steady linear increase in C ¯ L and C ¯ D was noted for upward-oriented inflows between 0 < J Vert < 0.3 and J Vert > 0.7, a significant unsteady wing-wake interaction occurred when 0.3 ≤ J Vert < 0.7, which caused large variations in instantaneous forces over the wing and led to a reduction in mean performance. These findings highlight asymmetrical effects of vertically oriented perturbations on the performance of flapping wings and pave the way for development of suitable control strategies.}, } @article {pmid34234155, year = {2021}, author = {Connolly, S and Newport, D and McGourty, K}, title = {Cell specific variation in viability in suspension in in vitro Poiseuille flow conditions.}, journal = {Scientific reports}, volume = {11}, number = {1}, pages = {13997}, pmid = {34234155}, issn = {2045-2322}, mesh = {Algorithms ; Cell Line, Tumor ; *Cell Survival ; Fibroblasts ; Humans ; *Lab-On-A-Chip Devices ; *Microfluidic Analytical Techniques ; *Models, Theoretical ; Neoplastic Cells, Circulating ; Suspensions ; T-Lymphocytes ; }, abstract = {The influence of Poiseuille flow on cell viability has applications in the areas of cancer metastasis, lab-on-a-chip devices and flow cytometry. Indeed, retaining cell viability is important in the emerging field of adoptive cell therapy, as cells need to be returned to patients' bodies, while the viability of other cells, which are perhaps less accustomed to suspension in a fluidic environment, is important to retain in flow cytometers and other such devices. Despite this, it is unclear how Poiseuille flow affects cell viability. Following on from previous studies which investigated the viability and inertial positions of circulating breast cancer cells in identical flow conditions, this study investigated the influence that varying flow rate, and the corresponding Reynolds number has on the viability of a range of different circulating cells in laminar pipe flow including primary T-cells, primary fibroblasts and neuroblastoma cells. It was found that Reynolds numbers as high as 9.13 had no effect on T-cells while the viabilities of neuroblastoma cells and intestinal fibroblasts were significantly reduced in comparison. This indicates that in vitro flow devices need to be tailored to cell-specific flow regimes.}, } @article {pmid34208685, year = {2021}, author = {Shanbrom, C and Balisacan, J and Wilkens, G and Chyba, M}, title = {Geometric Methods for Efficient Planar Swimming of Copepod Nauplii.}, journal = {Micromachines}, volume = {12}, number = {6}, pages = {}, pmid = {34208685}, issn = {2072-666X}, support = {359510//Simons Foundation/ ; }, abstract = {Copepod nauplii are larval crustaceans with important ecological functions. Due to their small size, they experience an environment of low Reynolds number within their aquatic habitat. Here we provide a mathematical model of a swimming copepod nauplius with two legs moving in a plane. This model allows for both rotation and two-dimensional displacement by the periodic deformation of the swimmer's body. The system is studied from the framework of optimal control theory, with a simple cost function designed to approximate the mechanical energy expended by the copepod. We find that this model is sufficiently realistic to recreate behavior similar to those of observed copepod nauplii, yet much of the mathematical analysis is tractable. In particular, we show that the system is controllable, but there exist singular configurations where the degree of non-holonomy is non-generic. We also partially characterize the abnormal extremals and provide explicit examples of families of abnormal curves. Finally, we numerically simulate normal extremals and observe some interesting and surprising phenomena.}, } @article {pmid34204328, year = {2021}, author = {Ali, A and Bukhari, Z and Umar, M and Ismail, MA and Abbas, Z}, title = {Cu and Cu-SWCNT Nanoparticles' Suspension in Pulsatile Casson Fluid Flow via Darcy-Forchheimer Porous Channel with Compliant Walls: A Prospective Model for Blood Flow in Stenosed Arteries.}, journal = {International journal of molecular sciences}, volume = {22}, number = {12}, pages = {}, pmid = {34204328}, issn = {1422-0067}, mesh = {Algorithms ; Arteries/pathology/physiopathology ; Blood Circulation ; Constriction, Pathologic ; *Copper/chemistry ; *Hemodynamics ; Humans ; *Hydrodynamics ; *Metal Nanoparticles/chemistry ; *Models, Cardiovascular ; Porosity ; *Pulsatile Flow ; Suspensions ; }, abstract = {The use of experimental relations to approximate the efficient thermophysical properties of a nanofluid (NF) with Cu nanoparticles (NPs) and hybrid nanofluid (HNF) with Cu-SWCNT NPs and subsequently model the two-dimensional pulsatile Casson fluid flow under the impact of the magnetic field and thermal radiation is a novelty of the current study. Heat and mass transfer analysis of the pulsatile flow of non-Newtonian Casson HNF via a Darcy-Forchheimer porous channel with compliant walls is presented. Such a problem offers a prospective model to study the blood flow via stenosed arteries. A finite-difference flow solver is used to numerically solve the system obtained using the vorticity stream function formulation on the time-dependent governing equations. The behavior of Cu-based NF and Cu-SWCNT-based HNF on the wall shear stress (WSS), velocity, temperature, and concentration profiles are analyzed graphically. The influence of the Casson parameter, radiation parameter, Hartmann number, Darcy number, Soret number, Reynolds number, Strouhal number, and Peclet number on the flow profiles are analyzed. Furthermore, the influence of the flow parameters on the non-dimensional numbers such as the skin friction coefficient, Nusselt number, and Sherwood number is also discussed. These quantities escalate as the Reynolds number is enhanced and reduce by escalating the porosity parameter. The Peclet number shows a high impact on the microorganism's density in a blood NF. The HNF has been shown to have superior thermal properties to the traditional one. These results could help in devising hydraulic treatments for blood flow in highly stenosed arteries, biomechanical system design, and industrial plants in which flow pulsation is essential.}, } @article {pmid34203635, year = {2021}, author = {Ju, Y and Zhu, T and Mashayekhi, R and Mohammed, HI and Khan, A and Talebizadehsardari, P and Yaïci, W}, title = {Evaluation of Multiple Semi-Twisted Tape Inserts in a Heat Exchanger Pipe Using Al2O3 Nanofluid.}, journal = {Nanomaterials (Basel, Switzerland)}, volume = {11}, number = {6}, pages = {}, pmid = {34203635}, issn = {2079-4991}, abstract = {The hydrothermal performance of multiple semi-twisted tape inserts inside a heat exchanger pipe is numerically examined in three-dimensions. This study aims to find the optimum case for having the highest heat transfer enhancement with the lowest friction factor using nanofluid (Al2O3/water). A performance evaluation criterion (PEC) is defined to characterize the performance based on both friction factor and heat transfer. It was found that increasing the number of semi-twisted tapes increases the number of swirl flow streams and leads to an enhancement in the local Nusselt number as well as the friction factor. The average Nusselt number increases from 15.13 to 28.42 and the average friction factor enhances from 0.022 to 0.052 by increasing the number of the semi-twisted tapes from 0 to 4 for the Reynolds number of 1000 for the base fluid. By using four semi-twisted tapes, the average Nusselt number increases from 12.5 to 28.5, while the friction factor reduces from 0.155 to 0.052 when the Reynolds number increases from 250 to 1000 for the base fluid. For the Reynolds number of 1000, the increase in nanofluid concentration from 0 to 3% improves the average Nusselt number and friction factor by 6.41% and 2.29%, respectively. The highest PEC is equal to 1.66 and belongs to the Reynolds number of 750 using four semi-twisted tape inserts with 3% nanoparticles. This work offers instructions to model an advanced design of twisted tape integrated with tubes using multiple semi-twisted tapes, which helps to provide a higher amount of energy demand for solar applications.}, } @article {pmid34199619, year = {2021}, author = {Elsafy, KM and Saghir, MZ}, title = {Forced Convection in Wavy Microchannels Porous Media Using TiO2 and Al2O3-Cu Nanoparticles in Water Base Fluids: Numerical Results.}, journal = {Micromachines}, volume = {12}, number = {6}, pages = {}, doi = {10.3390/mi12060654}, pmid = {34199619}, issn = {2072-666X}, abstract = {In the present work, an attempt is made to investigate the performance of three fluids with forced convection in a wavy channel. The fluids are water, a nanofluid of 1% TiO2 in a water solution and a hybrid fluid which consists of 1% Al2O3-Cu nanoparticles in a water solution. The wavy channel has a porous insert with a permeability of 10 PPI, 20 PPI and 40 PPI, respectively. Since Reynolds number is less than 1000, the flow is assumed laminar, Newtonian and steady state. Results revealed that wavy channel provides a better heat enhancement than a straight channel of the same dimension. Porous material increases heat extraction at the expenses of the pressure drop. The nanofluid of 1% TiO2 in water provided the highest performance evaluation criteria.}, } @article {pmid34185996, year = {2021}, author = {Ahmed, S and Perez-Mercader, J}, title = {Autonomous Low-Reynolds-Number Soft Robots with Structurally Encoded Motion and Their Thermodynamic Efficiency.}, journal = {Langmuir : the ACS journal of surfaces and colloids}, volume = {37}, number = {27}, pages = {8148-8156}, doi = {10.1021/acs.langmuir.1c00765}, pmid = {34185996}, issn = {1520-5827}, support = {1541959//National Science Foundation/ ; }, mesh = {Biocompatible Materials ; Motion ; *Robotics ; Thermodynamics ; }, abstract = {Soft low-Reynolds-number robotics hold the potential to significantly impact numerous fields including drug delivery, sensing, and diagnostics. Realizing this potential is predicated upon the ability to design soft robots tailored to their intended function. In this work, we identify the effect of different geometric and symmetry parameters on the motion of soft, autonomous robots that operate in the low-Reynolds-number regime and use organic fuel. The ability to power low-Reynolds-number soft robots using an organic fuel would provide a new avenue for their potential use in biomedical applications, as is the use of a polymeric biocompatible material as is done here. We introduce a simple and cost-effective 3D-printer-assisted method to fabricate robots of different shapes that is scalable and widely applicable for a variety of materials. The efficiency of chemical energy to mechanical energy conversion is measured in soft low-Reynolds-number robots for the first time, and their mechanism of motion is assessed. Motion is a result of a periodic and oscillatory change in the charge state of the gel. This work lays the groundwork for the structure-function design of soft, chemically operated, and autonomous low-Reynolds-number robots.}, } @article {pmid34184223, year = {2021}, author = {Yang, F and Zeng, YH and Huai, WX}, title = {A new model for settling velocity of non-spherical particles.}, journal = {Environmental science and pollution research international}, volume = {28}, number = {43}, pages = {61636-61646}, pmid = {34184223}, issn = {1614-7499}, support = {51879197//National Natural Science Foundation of China/ ; 51622905//National Natural Science Foundation of China/ ; 2016YFA0600901//National key research and development of China/ ; }, mesh = {*Ecosystem ; Particle Size ; }, abstract = {The settlement of non-spherical particles, such as propagules of plants and natural sediments, is commonly observed in riverine ecosystems. The settling process is influenced by both particle properties (size, density, and shape) and fluid properties (density and viscosity). Therefore, the drag law of non-spherical particles is a function of both particle Reynolds number and particle shape. Herein, a total of 828 settling data are collected from the literatures, which cover a wide range of particle Reynolds number (0.008-10000). To characterize the influence of particle shapes, sphericity is adopted as the general shape factor, which varies from 0.421 to 1.0. By comparing the measured drag with the standard drag curve of spheres, we modify the spherical drag law with three shape-dependent functions to develop a new drag law for non-spherical particles. Combined with an iterative procedure, a new model is thus obtained to predict the settling velocity of non-spherical particles of various shapes and materials. Further applications in hydrochorous propagule dispersal and sediment transport are projected based on deeper understanding of the settling process.}, } @article {pmid34143104, year = {2021}, author = {Hill, JL and Hsu, PS and Jiang, N and Grib, SW and Roy, S and Borg, M and Thomas, L and Reeder, M and Schumaker, SA}, title = {Hypersonic N2 boundary layer flow velocity profile measurements using FLEET.}, journal = {Applied optics}, volume = {60}, number = {15}, pages = {C38-C46}, doi = {10.1364/AO.417470}, pmid = {34143104}, issn = {1539-4522}, abstract = {Femtosecond laser electronic excitation tagging (FLEET) velocimetry was used in the boundary layer of an ogive-cylinder model in a Mach-6 Ludwieg tube. One-dimensional velocity profiles were extracted from the FLEET signal in laminar boundary layers from pure N2 flows at unit Reynolds numbers ranging from 3.4×106/m to3.9×106/m. The effects of model tip bluntness and the unit Reynolds number on the velocity profiles were investigated. The challenges and strategies of applying FLEET for direct boundary layer velocity measurement are discussed. The potential of utilizing FLEET velocimetry for understanding the dynamics of laminar and turbulent boundary layers in hypersonic flows is demonstrated.}, } @article {pmid34139680, year = {2021}, author = {Mazharmanesh, S and Stallard, J and Medina, A and Fisher, A and Ando, N and Tian, FB and Young, J and Ravi, S}, title = {Performance of passively pitching flapping wings in the presence of vertical inflows.}, journal = {Bioinspiration & biomimetics}, volume = {16}, number = {5}, pages = {}, doi = {10.1088/1748-3190/ac0c60}, pmid = {34139680}, issn = {1748-3190}, mesh = {Animals ; Biomechanical Phenomena ; *Flight, Animal ; *Models, Biological ; Wings, Animal ; }, abstract = {The successful implementation of passively pitching flapping wings strongly depends on their ability to operate efficiently in wind disturbances. In this study, we experimentally investigated the interaction between a uniform vertical inflow perturbation and a passive-pitching flapping wing using a Reynolds-scaled apparatus operating in water at Reynolds number ≈3600. A parametric study was performed by systematically varying the Cauchy number (Ch) of the wings from 0.09 to 11.52. The overall lift and drag, and pitch angle of the wing were measured by varying the magnitude of perturbation fromJVert= -0.6 (downward inflow) toJVert= 0.6 (upward inflow) at eachCh, whereJVertis the ratio of the inflow velocity to the wing's velocity. We found that the lift and drag had remarkably different characteristics in response to bothChandJVert. Across allCh, while mean lift tended to increase as the inflow perturbation varied from -0.6 to 0.6, drag was significantly less sensitive to the perturbation. However effect of the vertical inflow on drag was dependent onCh, where it tended to vary from an increasing to a decreasing trend asChwas changed from 0.09 to 11.52. The differences in the lift and drag with perturbation magnitude could be attributed to the reorientation of the net force over the wing as a result of the interaction with the perturbation. These results highlight the complex interactions between passively pitching flapping wings and freestream perturbations and will guide the design of miniature flying crafts with such architectures.}, } @article {pmid34134196, year = {2021}, author = {Li, H and Tian, B and He, Z and Zhang, Y}, title = {Growth mechanism of interfacial fluid-mixing width induced by successive nonlinear wave interactions.}, journal = {Physical review. E}, volume = {103}, number = {5-1}, pages = {053109}, doi = {10.1103/PhysRevE.103.053109}, pmid = {34134196}, issn = {2470-0053}, abstract = {Interfacial fluid mixing induced by successive waves, such as shock, rarefaction, and compression waves, plays a fundamental role in engineering applications, e.g., inertial confinement fusion, and in natural phenomena, e.g., supernova explosion. These waves bring nonuniform, unsteady external forces into the mixing zone, which leads to a complex mixing process. The growth rate of the mixing width is analyzed by decomposing the turbulent flow field into the averaged field and the fluctuating counterpart. The growth rate is thus divided into three parts: (i) the stretching or compression (S(C)) effect induced by the averaged-velocity difference between two ends of the mixing zone, (ii) the penetration effect induced by the fluctuations which represent the penetration of the two species into each other, and (iii) the diffusive effect, which is induced by the molecular diffusion and is negligible in high-Reynolds-number flows at Schmidt number of order unity. The penetration effect is further divided into the Richtmyer-Meshkov (RM) effect, which is induced by fluctuations that were deposited by earlier wave interactions, and the Rayleigh-Taylor (RT) effect, which is caused by the fluctuations that arise in an overall acceleration of the mixing zone. During the passage of the rarefaction waves, the mixing zone is stretched, while during the passage of the compression waves or shock waves, the mixing zone is compressed. To illustrate these effects, a physical model of RM mixing with reshock is used. By combining the S(C), RM, and RT effects, the entire evolution of mixing width is restructured, which agrees well with numerical simulations for problems with a wide range of density ratios.}, } @article {pmid34129919, year = {2021}, author = {Ahookhosh, K and Saidi, M and Mohammadpourfard, M and Aminfar, H and Hamishehkar, H and Farnoud, A and Schmid, O}, title = {Flow Structure and Particle Deposition Analyses for Optimization of a Pressurized Metered Dose Inhaler (pMDI) in a Model of Tracheobronchial Airway.}, journal = {European journal of pharmaceutical sciences : official journal of the European Federation for Pharmaceutical Sciences}, volume = {164}, number = {}, pages = {105911}, doi = {10.1016/j.ejps.2021.105911}, pmid = {34129919}, issn = {1879-0720}, mesh = {Administration, Inhalation ; Adult ; Aerosols ; Equipment Design ; Female ; Humans ; Lung ; *Metered Dose Inhalers ; *Nebulizers and Vaporizers ; Particle Size ; }, abstract = {Inhalation therapy plays an important role in management or treatment of respiratory diseases such asthma and chronic obstructive pulmonary diseases (COPDs). For decades, pressurized metered dose inhalers (pMDIs) have been the most popular and prescribed drug delivery devices for inhalation therapy. The main objectives of the present computational work are to study flow structure inside a pMDI, as well as transport and deposition of micron-sized particles in a model of human tracheobronchial airways and their dependence on inhalation air flow rate and characteristic pMDI parameters. The upper airway geometry, which includes the extrathoracic region, trachea, and bronchial airways up to the fourth generation in some branches, was constructed based on computed tomography (CT) images of an adult healthy female. Computational fluid dynamics (CFD) simulation was employed using the k-ω model with low-Reynolds number (LRN) corrections to accomplish the objectives. The deposition results of the present study were verified with the in vitro deposition data of our previous investigation on pulmonary drug delivery using a hollow replica of the same airway geometry as used for CFD modeling. It was found that the flow structure inside the pMDI and extrathoracic region strongly depends on inhalation flow rate and geometry of the inhaler. In addition, regional aerosol deposition patterns were investigated at four inhalation flow rates between 30 and 120 L/min and for 60 L/min yielding highest deposition fractions of 24.4% and 3.1% for the extrathoracic region (EX) and the trachea, respectively. It was also revealed that particle deposition was larger in the right branches of the bronchial airways (right lung) than the left branches (left lung) for all of the considered cases. Also, optimization of spray characteristics showed that the optimum values for initial spray velocity, spray cone angle and spray duration were 100 m/s, 10° and 0.1 sec, respectively. Moreover, spray cone angle, more than any other of the investigated pMDI parameters can change the deposition pattern of inhaled particles in the airway model. In conclusion, the present investigation provides a validated CFD model for particle deposition and new insights into the relevance of flow structure for deposition of pMDI-emitted pharmaceutical aerosols in the upper respiratory tract.}, } @article {pmid34127716, year = {2021}, author = {Shah, Z and Jafaryar, M and Sheikholeslami, M and Ikramullah, and Kumam, P}, title = {Heat transfer intensification of nanomaterial with involve of swirl flow device concerning entropy generation.}, journal = {Scientific reports}, volume = {11}, number = {1}, pages = {12504}, pmid = {34127716}, issn = {2045-2322}, abstract = {The thermal features of hybrid nano-powder turbulent motion through a pipe employing helical turbulator is numerically simulated via Finite Volume Method (FVM). The hybrid nanofluid (MWCNTs + Fe3O4 + H2O) is obtained by uniformly dispersing MWCNTs + Fe3O4 nanomaterials in H2O. The characteristics features of thermal energy transfer of hybrid nanofluid are investigated by varying the pitch ratio (P) of the helical turbulator and Reynolds number (Re) of the fluid. The outputs of the study are depicted in terms of contour plots of temperature, velocity, frictional irreversibility Sgen,f, and thermal irreversibility Sgen,th. The variation of Sgen,f, and Sgen,th with changing P and Re are also displayed by 3D plots. It is found that making the fluid more turbulent by increasing Re, the temperature of the fluid drops whereas the fluid velocity augments. The frictional irreversibility enhances, whereas the thermal irreversibility drops with the increasing turbulent motion. The decreasing P causes to drop the temperature of the higher turbulent fluid flow, while opposite effect is observed for smaller Re. The decreasing P causes to enhance the fluid mixing and thus augments the fluid velocity. Sgen,f and Sgen,th both augment with decreasing P. The comparison of current outputs with the older article shows an acceptable accuracy. The results of the present investigation will be useful in modelling of efficient thermal energy transfer systems.}, } @article {pmid34124445, year = {2021}, author = {Tian, G and Zhu, Y and Feng, X and Zhou, H and Zhang, Y}, title = {Investigation of the Turbulent Boundary Layer Structure over a Sparsely Spaced Biomimetic Spine-Covered Protrusion Surface.}, journal = {ACS omega}, volume = {6}, number = {22}, pages = {14220-14229}, pmid = {34124445}, issn = {2470-1343}, abstract = {Multiperspective particle image velocimetry was used to investigate the turbulent boundary layer structure over biomimetic spine-covered protrusion (BSCP) samples inspired by dorsal skin of pufferfish. The comparison of BSCP samples of two sparse "k-type" arrangements (aligned and staggered) with roughness height k + = 5-7 (nearly hydraulically smooth) and smooth case were manufactured in bulk Reynolds number Re b = 37,091, 44,510. The negative value of the roughness function ΔU + shows a downward shift of the mean velocity profile of BSCP samples, which shows a drag reduction effect. The results of turbulent statistics present strong fluctuation over the aligned case in the streamwise direction, while little influence is observed in the wall-normal and spanwise direction, which promotes turbulence stability. The same phenomenon was found based on the probability density function of fluctuation velocity that the suppression of turbulent flow is better over the staggered case. It is obvious that the shear stress induced is governed by the streamwise fluctuations. Furthermore, the Q-criterion and the λci-criterion improved with vorticity ω were introduced for vortex identification, which indicates less prograde vortex population and weaker swirling strength over BSCP samples than over the smooth one. Finally, the spatial coherent structure appeared similar and more orderly over the staggered case in the streamwise and wall-normal direction based on the analysis of two-point correlations R uu. These results provide further guidance to reveal the mechanism of drag reduction on the BSCP surface.}, } @article {pmid34111118, year = {2021}, author = {Velho Rodrigues, MF and Lisicki, M and Lauga, E}, title = {The bank of swimming organisms at the micron scale (BOSO-Micro).}, journal = {PloS one}, volume = {16}, number = {6}, pages = {e0252291}, pmid = {34111118}, issn = {1932-6203}, mesh = {Biodiversity ; Biomechanical Phenomena ; Flagella ; Locomotion ; *Microbiology ; Swimming ; }, abstract = {Unicellular microscopic organisms living in aqueous environments outnumber all other creatures on Earth. A large proportion of them are able to self-propel in fluids with a vast diversity of swimming gaits and motility patterns. In this paper we present a biophysical survey of the available experimental data produced to date on the characteristics of motile behaviour in unicellular microswimmers. We assemble from the available literature empirical data on the motility of four broad categories of organisms: bacteria (and archaea), flagellated eukaryotes, spermatozoa and ciliates. Whenever possible, we gather the following biological, morphological, kinematic and dynamical parameters: species, geometry and size of the organisms, swimming speeds, actuation frequencies, actuation amplitudes, number of flagella and properties of the surrounding fluid. We then organise the data using the established fluid mechanics principles for propulsion at low Reynolds number. Specifically, we use theoretical biophysical models for the locomotion of cells within the same taxonomic groups of organisms as a means of rationalising the raw material we have assembled, while demonstrating the variability for organisms of different species within the same group. The material gathered in our work is an attempt to summarise the available experimental data in the field, providing a convenient and practical reference point for future studies.}, } @article {pmid34091219, year = {2021}, author = {Amani, M and Amani, P and Bahiraei, M and Ghalambaz, M and Ahmadi, G and Wang, LP and Wongwises, S and Mahian, O}, title = {Latest developments in nanofluid flow and heat transfer between parallel surfaces: A critical review.}, journal = {Advances in colloid and interface science}, volume = {294}, number = {}, pages = {102450}, doi = {10.1016/j.cis.2021.102450}, pmid = {34091219}, issn = {1873-3727}, abstract = {The enhancement of heat transfer between parallel surfaces, including parallel plates, parallel disks, and two concentric pipes, is vital because of their wide applications ranging from lubrication systems to water purification processes. Various techniques can be utilized to enhance heat transfer in such systems. Adding nanoparticles to the conventional working fluids is an effective solution that could remarkably enhance the heat transfer rate. No published review article focuses on the recent advances in nanofluid flow between parallel surfaces; therefore, the present paper aims to review the latest experimental and numerical studies on the flow and heat transfer of nanofluids (mixtures of nanoparticles and conventional working fluids) in such configurations. For the performance analysis of thermal systems composed of parallel surfaces and operating with nanofluids, it is necessary to know the physical phenomena and parameters that influence the flow and heat transfer characteristics in these systems. Significant results obtained from this review indicate that, in most cases, the heat transfer rate between parallel surfaces is enhanced with an increase in the Rayleigh number, the Reynolds number, the magnetic number, and Brownian motion. On the other hand, an increase in thermophoresis parameter, as well as flow parameters, including the Eckert number, buoyancy ratio, Hartmann number, and Lewis number, leads to heat transfer rate reduction.}, } @article {pmid34081994, year = {2021}, author = {Das, S and Pal, TK and Jana, RN and Giri, B}, title = {Significance of Hall currents on hybrid nano-blood flow through an inclined artery having mild stenosis: Homotopy perturbation approach.}, journal = {Microvascular research}, volume = {137}, number = {}, pages = {104192}, doi = {10.1016/j.mvr.2021.104192}, pmid = {34081994}, issn = {1095-9319}, mesh = {Animals ; Arterial Occlusive Diseases/*physiopathology ; Arteries/*physiopathology ; Constriction, Pathologic ; Copper/*chemistry ; *Hemodynamics ; Humans ; *Metal Nanoparticles ; *Models, Cardiovascular ; *Nanotechnology ; Porosity ; Regional Blood Flow ; Stress, Mechanical ; }, abstract = {The rheological perspective of blood flow with the suspension of metallic or non-metallic nanoparticles through arteries having cardiovascular diseases is getting more attention due to momentous applications in obstructed hemodynamics, nano-hemodynamics, nano-pharmacology, blood purification system, treatment of hemodynamic ailments, etc. Motivated by the novel significance and research in this direction, a mathematical hemodynamics model is developed to mimic the hemodynamic features of blood flow under the concentration of hybrid nanoparticles through an inclined artery with mild stenosis in the existence of dominating electromagnetic field force, Hall currents, heat source, and porous substance. Copper (Cu) and copper oxide (CuO) nanoparticles are submerged into the blood to form hybrid nano-blood suspension (Cu-CuO/blood). The attribute of the medium porosity on the blood flow is featured by Darcy's law. The mathematical equations describing the flow are formulated and simplified under mild stenosis and small Reynolds number assumptions. To determine the analytical solution of the resulting nonlinear momentum equation, the homotopy perturbation method (HPM) is employed. Several figures are graphed to assess the hemodynamical contributions of various intricate physical parameters on blood flow phenomena through the inclined stenosed artery. Significant outcomes from graphical elucidation envisage that the hemodynamic resistance to the blood flow is reduced due to the dispersion of more hybrid nanoparticles in the blood. The hemodynamic resistance (impedance) increases approximately two times by dispersing 0.11% hybrid nanoparticles in the blood flow. The temperature of Cu-CuO/blood is found to be lower in comparison to Cu-blood and pure blood. Intensification of Hall parameter attenuates the wall shear stress at the arterial wall. The trapping phenomena are also outlined via streamline plots which exemplify the blood flow pattern in the stenosed artery under the variation of the emerging parameters. As anticipated, the addition of a large number of hybrid nanoparticles significantly modulates the blood flow pattern in the stenotic region. The novel feature of this model is the impressive impact of Hall currents on hybrid nanoparticle doped blood flow through the stenosed artery. There is another piece of significance is that HPM is the most suitable method to handle the nonlinear momentum equation under the aforementioned flow constraints. Outcomes of this simulation may be valuable for advanced study and research in biomedical engineering, bio-nanofluid mechanics, nano-pharmacodynamics.}, } @article {pmid34078976, year = {2021}, author = {Usman, AH and Khan, NS and Humphries, UW and Ullah, Z and Shah, Q and Kumam, P and Thounthong, P and Khan, W and Kaewkhao, A and Bhaumik, A}, title = {Computational optimization for the deposition of bioconvection thin Oldroyd-B nanofluid with entropy generation.}, journal = {Scientific reports}, volume = {11}, number = {1}, pages = {11641}, pmid = {34078976}, issn = {2045-2322}, abstract = {The behavior of an Oldroyd-B nanoliquid film sprayed on a stretching cylinder is investigated. The system also contains gyrotactic microorganisms with heat and mass transfer flow. Similarity transformations are used to make the governing equations non-dimensional ordinary differential equations and subsequently are solved through an efficient and powerful analytic technique namely homotopy analysis method (HAM). The roles of all dimensionless profiles and spray rate have been investigated. Velocity decreases with the magnetic field strength and Oldroyd-B nanofluid parameter. Temperature is increased with increasing the Brownian motion parameter while it is decreased with the increasing values of Prandtl and Reynolds numbers. Nanoparticle's concentration is enhanced with the higher values of Reynolds number and activation energy parameter. Gyrotactic microorganism density increases with bioconvection Rayleigh number while it decreases with Peclet number. The film size naturally increases with the spray rate in a nonlinear way. A close agreement is achieved by comparing the present results with the published results.}, } @article {pmid34076781, year = {2021}, author = {Kadiri, VM and Günther, JP and Kottapalli, SN and Goyal, R and Peter, F and Alarcón-Correa, M and Son, K and Barad, HN and Börsch, M and Fischer, P}, title = {Light- and magnetically actuated FePt microswimmers.}, journal = {The European physical journal. E, Soft matter}, volume = {44}, number = {6}, pages = {74}, pmid = {34076781}, issn = {1292-895X}, support = {253407113//Deutsche Forschungsgemeinschaft/ ; }, abstract = {Externally controlled microswimmers offer prospects for transport in biological research and medical applications. This requires biocompatibility of the swimmers and the possibility to tailor their propulsion mechanisms to the respective low Reynolds number environment. Here, we incorporate low amounts of the biocompatible alloy of iron and platinum (FePt) in its [Formula: see text] phase in microstructures by a versatile one-step physical vapor deposition process. We show that the hard magnetic properties of [Formula: see text] FePt are beneficial for the propulsion of helical micropropellers with rotating magnetic fields. Finally, we find that the FePt coatings are catalytically active and also make for Janus microswimmers that can be light-actuated and magnetically guided.}, } @article {pmid34069236, year = {2021}, author = {Choe, YW and Sim, SB and Choo, YM}, title = {New Equation for Predicting Pipe Friction Coefficients Using the Statistical Based Entropy Concepts.}, journal = {Entropy (Basel, Switzerland)}, volume = {23}, number = {5}, pages = {}, doi = {10.3390/e23050611}, pmid = {34069236}, issn = {1099-4300}, abstract = {In general, this new equation is significant for designing and operating a pipeline to predict flow discharge. In order to predict the flow discharge, accurate determination of the flow loss due to pipe friction is very important. However, existing pipe friction coefficient equations have difficulties in obtaining key variables or those only applicable to pipes with specific conditions. Thus, this study develops a new equation for predicting pipe friction coefficients using statistically based entropy concepts, which are currently being used in various fields. The parameters in the proposed equation can be easily obtained and are easy to estimate. Existing formulas for calculating pipe friction coefficient requires the friction head loss and Reynolds number. Unlike existing formulas, the proposed equation only requires pipe specifications, entropy value and average velocity. The developed equation can predict the friction coefficient by using the well-known entropy, the mean velocity and the pipe specifications. The comparison results with the Nikuradse's experimental data show that the R2 and RMSE values were 0.998 and 0.000366 in smooth pipe, and 0.979 to 0.994 or 0.000399 to 0.000436 in rough pipe, and the discrepancy ratio analysis results show that the accuracy of both results in smooth and rough pipes is very close to zero. The proposed equation will enable the easier estimation of flow rates.}, } @article {pmid34064079, year = {2021}, author = {Zhou, T and Chen, B and Liu, H}, title = {Study of the Performance of a Novel Radiator with Three Inlets and One Outlet Based on Topology Optimization.}, journal = {Micromachines}, volume = {12}, number = {6}, pages = {}, doi = {10.3390/mi12060594}, pmid = {34064079}, issn = {2072-666X}, abstract = {In recent years, in order to obtain a radiator with strong heat exchange capacity, researchers have proposed a lot of heat exchangers to improve heat exchange capacity significantly. However, the cooling abilities of heat exchangers designed by traditional design methods is limited even if the geometric parameters are optimized at the same time. However, using topology optimization to design heat exchangers can overcome this design limitation. Furthermore, researchers have used topology optimization theory to designed one-to-one and many-to-many inlet and outlet heat exchangers because it can effectively increase the heat dissipation rate. In particular, it can further decrease the hot-spot temperature for many-to-many inlet and outlet heat exchangers. Therefore, this article proposes novel heat exchangers with three inlets and one outlet designed by topology optimization to decrease the fluid temperature at the outlet. Subsequently, the effect of the channel depth on the heat exchanger design is also studied. The results show that the type of exchanger varies with the channel depth, and there exists a critical depth value for obtaining the minimum substrate temperature difference. Then, the flow and heat transfer performance of the heat exchangers are numerically investigated. The numerical results show that the heat exchanger derived by topology optimization with the minimum temperature difference as the goal (Model-2) is the best design for flow and heat transfer performance compared to other heat sink designs, including the heat exchanger derived by topology optimization having the average temperature as the goal (Model-1) and conventional straight channels (Model-3). The temperature difference of Model-1 can be reduced by 37.5%, and that of Model-2 can be decreased by 62.5% compared to Model-3. Compared with Model-3, the thermal resistance of Model-1 can be reduced by 21.86%, while that of Model-2 can be decreased by 47.99%. At room temperature, we carried out the forced convention experimental test for Model-2 to measure its physical parameters (temperature, pressure drop) to verify the numerical results. The error of the average wall temperature between experimental results and simulation results is within 2.6 K, while that of the fluid temperature between the experimental and simulation results is within 1.4 K, and the maximum deviation of the measured Nu and simulated Nu was less than 5%. This indicated that the numerical results agreed well with the experimental results.}, } @article {pmid34062924, year = {2021}, author = {Gu, B and Adjiman, CS and Xu, XY}, title = {Correlations for Concentration Polarization and Pressure Drop in Spacer-Filled RO Membrane Modules Based on CFD Simulations.}, journal = {Membranes}, volume = {11}, number = {5}, pages = {}, pmid = {34062924}, issn = {2077-0375}, support = {na//BP International Centre for Advanced Materials (BP-ICAM)/ ; }, abstract = {Empirical correlations for mass transfer coefficient and friction factor are often used in process models for reverse osmosis (RO) membrane systems. These usually involve four dimensionless groups, namely Reynolds number (Re), Sherwood number (Sh), friction factor (f), and Schmidt number (Sc), with the associated coefficients and exponents being obtained by fitting to experimental data. However, the range of geometric and operating conditions covered by the experiments is often limited. In this study, new dimensionless correlations for concentration polarization (CP) modulus and friction factor are presented, which are obtained by dimensional analysis and using simulation data from computational fluid dynamics (CFD). Two-dimensional CFD simulations are performed on three configurations of spacer-filled channels with 76 combinations of operating and geometric conditions for each configuration, covering a broad range of conditions encountered in RO membrane systems. Results obtained with the new correlations are compared with those from existing correlations in the literature. There is good consistency in the predicted CP with mean discrepancies less than 6%, but larger discrepancies for pressure gradient are found among the various friction factor correlations. Furthermore, the new correlations are implemented in a process model with six spiral wound modules in series and the predicted recovery, pressure drop, and specific energy consumption are compared with a reference case obtained by ROSA (Reverse Osmosis System Analysis, The Dow Chemical Company). Differences in predicted recovery and pressure drop are up to 5% and 83%, respectively, highlighting the need for careful selection of correlations when using predictive models in process design. Compared to existing mass transfer correlations, a distinct advantage of our correlations for CP modulus is that they can be directly used to estimate the impact of permeate flux on CP at a membrane surface without having to resort to the film theory.}, } @article {pmid34059714, year = {2021}, author = {Pang, M and Zhang, T and Guo, Y and Zhang, L}, title = {Re-crushing process and non-Darcian seepage characteristics of broken coal medium in coal mine water inrush.}, journal = {Scientific reports}, volume = {11}, number = {1}, pages = {11380}, pmid = {34059714}, issn = {2045-2322}, support = {51774234//Study on the Mechanism of Water-Gas Coupling Fracture Expansion and Ultrasonic Characteristics of Coal Rock Mass in Drilling Holes/ ; 2021JM-390//Fracture Evolution and Water-Gas Coupled Permeability Mechanism of Coal Body Around Extraction Borehole/ ; }, abstract = {The initiation process of the mine water inrush accident, the essence of this process is the sudden change of the seepage state of the broken coal medium under pressure and the instability of the skeleton. In order to study the re-crushing mechanism and seepage characteristics of the broken coal medium under load, a set of three-axis seepage system was designed independently. Using the steady-state infiltration method, multiple flow factors under different particle size combinations and different stress conditions of the broken coal medium were obtained. The results of the study indicate: in one hand, the reduction of the porosity of the broken coal medium will cause the flow channel to be rebuilt, and the sudden change of flow rate will directly lead to the non-Darcian flow behavior. The early stage of compaction mainly affects the permeability k value, and the later stage of compaction mainly affects the non-Darcian β value; On the other hand, the seepage throat in the broken coal medium may have a sharp increase in its flow rate, leading to a sudden change in the flow pattern. The critical Reynolds number is also used to determine whether non-Darcian flow is formed, and its value in the water inrush system is about 40-133; at the same time, the non-Darcian flow in the broken coal medium conforms to the Forchheimer-type flow law. By analyzing the dependence relationship between factors, a seepage factor representation algebraic relationship suitable for Forchheimer type non-Darcian flow of broken coal medium is given, which can be used as a calculation basis in the prevention and treatment of mine water inrush accidents.}, } @article {pmid34056212, year = {2021}, author = {Agarwal, JR and Torres, CF and Shah, S}, title = {Development of Dimensionless Parameters and Groups of Heat and Mass Transfer to Predict Wax Deposition in Crude Oil Pipelines.}, journal = {ACS omega}, volume = {6}, number = {16}, pages = {10578-10591}, doi = {10.1021/acsomega.0c05966}, pmid = {34056212}, issn = {2470-1343}, abstract = {A new methodology has been developed for analyzing heat and mass transfer to predict wax deposition in crude oil pipelines using the law of the wall dimensionless parameters. A set of physically meaningful dimensionless groups and parameters has laid a strong foundation behind the proposed methodology. The paper presents a discussion regarding the development of scale-up correlations from laboratory scale to field scale, considering the combination of both analytical groups and empirical correlations. Data from previous literature studies were employed for determining realistic values for the developed parameters and scale-up correlations. The utilization of new dimensionless scale-up parameters indicated that the wax deposition in crude oil pipelines is independent of the Reynolds number and the inner diameter of the pipeline. It further indicates that wax deposition in crude oil pipelines is mainly dependent on the heat transfer process and not on the shear reduction process. The dimensionless technique developed here can be utilized for determining the optimum pipe size and pigging frequencies to reduce and mitigate the effect of the wax deposition process.}, } @article {pmid34050744, year = {2021}, author = {Ford, MP and Santhanakrishnan, A}, title = {Closer Appendage Spacing Augments Metachronal Swimming Speed by Promoting Tip Vortex Interactions.}, journal = {Integrative and comparative biology}, volume = {61}, number = {5}, pages = {1608-1618}, doi = {10.1093/icb/icab112}, pmid = {34050744}, issn = {1557-7023}, mesh = {Animals ; Biomechanical Phenomena ; *Extremities ; Hydrodynamics ; Invertebrates ; *Swimming ; }, abstract = {Numerous species of aquatic invertebrates, including crustaceans, swim by oscillating multiple closely spaced appendages. The coordinated, out-of-phase motion of these appendages, known as "metachronal paddling," has been well-established to improve swimming performance relative to synchronous paddling. Invertebrates employing this propulsion strategy cover a wide range of body sizes and shapes, but the ratio of appendage spacing (G) to the appendage length (L) has been reported to lie in a comparatively narrow range of 0.2 < G/L ≤ 0.65. The functional role of G/L on metachronal swimming performance is unknown. We hypothesized that for a given Reynolds number and stroke amplitude, hydrodynamic interactions promoted by metachronal stroke kinematics with small G/L can increase forward swimming speed. We used a dynamically scaled self-propelling robot to comparatively examine swimming performance and wake development of metachronal and synchronous paddling under varying G/L, phase lag, and stroke amplitude. G/L was varied from 0.4 to 1.5, with the expectation that when G/L is large, there should be no performance difference between metachronal and synchronous paddling due to a lack of interaction between vortices that form on the appendages. Metachronal stroking at nonzero phase lag with G/L in the biological range produced faster swimming speeds than synchronous stroking. As G/L increased and as stroke amplitude decreased, the influence of phase lag on the swimming speed of the robot was reduced. For smaller G/L, vortex interactions between adjacent appendages generated a horizontally oriented wake and increased momentum fluxes relative to larger G/L, which contributed to increasing swimming speed. We find that while metachronal motion augments swimming performance for closely spaced appendages (G/L <1), moderately spaced appendages (1.0 ≤ G/L ≤ 1.5) can benefit from the metachronal motion only when the stroke amplitude is large.}, } @article {pmid34035439, year = {2021}, author = {Shankar, BM and Shivakumara, IS}, title = {Benchmark solution for the stability of plane Couette flow with net throughflow.}, journal = {Scientific reports}, volume = {11}, number = {1}, pages = {10901}, pmid = {34035439}, issn = {2045-2322}, abstract = {This paper investigates the stability of an incompressible viscous fluid flow between relatively moving horizontal parallel plates in the presence of a uniform vertical throughflow. A linear stability analysis has been performed by employing the method of normal modes and the resulting stability equation is solved numerically using the Chebyshev collocation method. Contrary to the stability of plane Couette flow (PCF) to small disturbances for all values of the Reynolds number in the absence of vertical throughflow, it is found that PCF becomes unstable owing to the change in the sign of growth rate depending on the magnitude of throughflow. The critical Reynolds number triggering the instability is computed for different values of throughflow dependent Reynolds number and it is shown that throughflow instills both stabilizing and destabilizing effect on the base flow. It is seen that the direction of throughflow has no influence on the stability of fluid flow. A comparative study between plane Poiseuille flow and PCF has also been carried out and the similarities and differences are highlighted.}, } @article {pmid34034247, year = {2021}, author = {Kasoju, VT and Santhanakrishnan, A}, title = {Pausing after clap reduces power required to fling wings apart at low Reynolds number.}, journal = {Bioinspiration & biomimetics}, volume = {16}, number = {5}, pages = {}, doi = {10.1088/1748-3190/ac050a}, pmid = {34034247}, issn = {1748-3190}, mesh = {Animals ; Biomechanical Phenomena ; *Flight, Animal ; Insecta ; Models, Biological ; *Thysanoptera ; Wings, Animal ; }, abstract = {The smallest flying insects, such as thrips (body length < 2 mm), are challenged with needing to move in air at a chord-based Reynolds number (Rec) of the order of 10. Pronounced viscous dissipation at such a low Recrequires considerable energetic expenditure for tiny insects to stay aloft. Thrips flap their densely bristled wings at large stroke amplitudes, bringing both wings in close proximity to each other at the end of upstroke ('clap') and moving their wings apart at the start of downstroke ('fling'). From high-speed videos of free take-off flights of thrips, we observed that their forewings remain clapped for approximately 10% of the wingbeat cycle before the start of downstroke (fling stroke). We sought to examine if there are aerodynamic advantages associated with pausing wing motion after upstroke (clap stroke) and before downstroke (fling stroke) at Rec= 10. A dynamically scaled robotic clap and fling platform was used to measure lift and drag forces generated by physical models of solid (non-bristled) and bristled wings in single wing and wing pair configurations, for pause times ranging between 0% to 41% of the cycle. For solid and bristled wing pairs, pausing before the start of downstroke (fling stroke) dissipated vorticity generated at the end of upstroke (clap stroke). This resulted in a decrease in the drag coefficient averaged across downstroke (fling stroke) and in turn reduced power requirements. Also, increasing the pause time resulted in a larger decrease in the dimensionless power coefficient for the wing-pair configurations compared to the single-wing configurations. Our findings show that wing-wing interaction observed in the clap and fling motion of tiny insect wings is necessary to realize the aerodynamic benefits of pausing before fling, by reducing the power required to clap and fling for a small compromise in lift.}, } @article {pmid34030500, year = {2021}, author = {Wanzheng, A and Pengfei, Z}, title = {Correction and laboratory investigation for energy loss coefficient of square-edged orifice plate.}, journal = {Science progress}, volume = {104}, number = {2}, pages = {368504211018571}, doi = {10.1177/00368504211018571}, pmid = {34030500}, issn = {2047-7163}, abstract = {A lot of studies have shown that the hydraulic characteristics of orifice plate are mainly controlled by its contraction ratio, but the thickness of square-edged orifice plate also has many impacts on energy loss characteristics. The primary objective of this study was to investigated the effects of square-edged orifice plate thickness on energy loss characteristics. In this paper, the effects of square-edged orifice plate thickness on energy loss characteristics are investigated by numerical simulation using CFD. Orifice plate discharge tunnel is axial symmetric, two dimensional numerical simulations of orifice plate discharge tunnel flow was used. The equation (9) for calculating energy loss coefficient of square-edged orifice plate energy dissipater considering the influence of thickness is proposed. The results of the present research demonstrate that energy loss coefficient decreases with increase of the orifice plate thickness. The results of model experiment are consistence with the results calculated by using rectified equation in present paper. The CFD simulations and Model experiment for the flow through an orifice plate are carried out. For square-edged orifice plate energy dissipater, the relative orifice plate thickness T/D has remarkable impacts on its energy loss coefficient ξ. The Traditional equation (8) is corrected by numerical results. The equation (9) for calculating energy loss coefficient of square-edged orifice plate energy dissipater considering the influence of thickness is proposed and this equation is available in the condition of d/D = 0.4-0.8, T/D = 0.05-0.25, and Re > 105(Re is Reynolds number). Comparing with the physical model experimental data, the relative errors of equation (9) is smaller than 15%.}, } @article {pmid34026737, year = {2021}, author = {Murayama, Y and Nakata, T and Liu, H}, title = {Flexible Flaps Inspired by Avian Feathers Can Enhance Aerodynamic Robustness in low Reynolds Number Airfoils.}, journal = {Frontiers in bioengineering and biotechnology}, volume = {9}, number = {}, pages = {612182}, pmid = {34026737}, issn = {2296-4185}, abstract = {Unlike rigid rotors of drones, bird wings are composed of flexible feathers that can passively deform while achieving remarkable aerodynamic robustness in response to wind gusts. In this study, we conduct an experimental study on the effects of the flexible flaps inspired by the covert of bird wings on aerodynamic characteristics of fixed-wings in disturbances. Through force measurements and flow visualization in a low-speed wind tunnel, it is found that the flexible flaps can suppress the large-scale vortex shedding and hence reduce the fluctuations of aerodynamic forces in a disturbed flow behind an oscillating plate. Our results demonstrate that the stiffness of the flaps strongly affects the aerodynamic performance, and the force fluctuations are observed to be reduced when the deformation synchronizes with the strong vortex generation. The results point out that the simple attachment of the flexible flaps on the upper surface of the wing is an effective method, providing a novel biomimetic design to improve the aerodynamic robustness of small-scale drones with fixed-wings operating in unpredictable aerial environments.}, } @article {pmid34024939, year = {2021}, author = {Chassagne, F and Barbour, MC and Chivukula, VK and Machicoane, N and Kim, LJ and Levitt, MR and Aliseda, A}, title = {The effect of Dean, Reynolds, and Womersley number on the flow in a spherical cavity on a curved round pipe. Part 1. Fluid mechanics in the cavity as a canonical flow representing intracranial aneurysms.}, journal = {Journal of fluid mechanics}, volume = {915}, number = {}, pages = {}, pmid = {34024939}, issn = {0022-1120}, support = {18CDA34110295/AHA/American Heart Association-American Stroke Association/United States ; R01 NS088072/NS/NINDS NIH HHS/United States ; R01 NS105692/NS/NINDS NIH HHS/United States ; R03 NS078539/NS/NINDS NIH HHS/United States ; }, abstract = {Flow in side-wall cerebral aneurysms can be ideally modelled as the combination of flow over a spherical cavity and flow in a curved circular pipe, two canonical flows. Flow in a curved pipe is known to depend on the Dean number De, combining the effects of Reynolds number, Re, and of the curvature along the pipe centreline, κ. Pulsatility in the flow introduces a dependency on the Womersley number Wo. Using stereo PIV measurements, this study investigated the effect of these three key non-dimensional parameters, by modifying pipe curvature (De), flow-rate (Re), and pulsatility frequency (Wo), on the flow patterns in a spherical cavity. A single counter-rotating vortex was observed in the cavity for all values of pipe curvature κ and Re, for both steady and pulsatile inflow conditions. Increasing the pipe curvature impacted both the flow patterns in the pipe and the cavity, by shifting the velocity profile towards the cavity opening and increasing the flow rate into the cavity. The circulation in the cavity was found to collapse well with only the Dean number, for both steady and pulsatile inflows. For pulsatile inflow, the counter-rotating vortex was unstable and the location of its centre over time was impacted by the curvature of the pipe, as well as the Re and the Wo in the freestream. The circulation in the cavity was higher for steady inflow than for the equivalent average Reynolds and Dean number pulsatile inflow, with very limited impact of the Womersley in the range studied.}, } @article {pmid34007926, year = {2021}, author = {Aljabair, S and Ekaid, AL and Ibrahim, SH and Alesbe, I}, title = {Mixed convection in sinusoidal lid driven cavity with non-uniform temperature distribution on the wall utilizing nanofluid.}, journal = {Heliyon}, volume = {7}, number = {5}, pages = {e06907}, pmid = {34007926}, issn = {2405-8440}, abstract = {Mixed convection heat transfer of Cu-water nanofluid in an arc cavity with non-uniform heating has been numerically studied. The top flat moving wall is isothermally cooled at Tc and moved with a constant velocity. While the heated arc stationary wall of the cavity is maintained at a hot temperature Th. FORTRAN code is used to solve the mass, momentum, and energy equations in dimensionless form with suitable boundary conditions. In this study, the Reynolds number changed from 1 to 2000, and the Rayleigh number changed from 0 to 107. Also, the range of nanoparticles volume fraction extends from ϕ = 0 to 0.07. Stream vorticity method selected for the discretization of flow and energy equations. The present results are compared with the previous results for the validation part, where the results found a good agreement with the others works. The isotherms are regulated near the arc-shape wall causing a steep temperature gradient at these regions and the local and average heat transfer rate increases with increased volume fraction or Reynolds number or Rayleigh number. Finally, Correlation equations of the average Nusselt number from numerical results are presented.}, } @article {pmid34006011, year = {2021}, author = {Fouxon, I and Feinberg, J and Mond, M}, title = {Linear and nonlinear hydromagnetic stability in laminar and turbulent flows.}, journal = {Physical review. E}, volume = {103}, number = {4-1}, pages = {043104}, doi = {10.1103/PhysRevE.103.043104}, pmid = {34006011}, issn = {2470-0053}, abstract = {We consider the evolution of arbitrarily large perturbations of a prescribed pure hydrodynamical flow of an electrically conducting fluid. We study whether the flow perturbations as well as the generated magnetic fields decay or grow with time and constitute a dynamo process. For that purpose we derive a generalized Reynolds-Orr equation for the sum of the kinetic energy of the hydrodynamic perturbation and the magnetic energy. The flow is confined in a finite volume so the normal component of the velocity at the boundary is zero. The tangential component is left arbitrary in contrast with previous works. For the magnetic field we mostly employ the classical boundary conditions where the field extends in the whole space. We establish critical values of hydrodynamic and magnetic Reynolds numbers below which arbitrarily large initial perturbations of the hydrodynamic flow decay. This involves generalization of the Rayleigh-Faber-Krahn inequality for the smallest eigenvalue of an elliptic operator. For high Reynolds number turbulence we provide an estimate of critical magnetic Reynolds number below which arbitrarily large fluctuations of the magnetic field decay.}, } @article {pmid34005982, year = {2021}, author = {Gissinger, JR and Zinchenko, AZ and Davis, RH}, title = {Internal circulation and mixing within tight-squeezing deformable droplets.}, journal = {Physical review. E}, volume = {103}, number = {4-1}, pages = {043106}, doi = {10.1103/PhysRevE.103.043106}, pmid = {34005982}, issn = {2470-0053}, abstract = {The internal flow and mixing properties inside deformable droplets, after reaching the steady state within two types of passive droplet traps, are visualized and analyzed as dynamical systems. The first droplet trap (constriction) is formed by three spheres arranged in an equilateral triangle, while the second consists of two parallel spherocylinders (capsules). The systems are assumed to be embedded in a uniform far-field flow at low Reynolds number, and the steady shapes and interfacial velocities on the drops are generated using the boundary-integral method. The internal velocity field is recovered by solving the internal Dirichlet problem, also via a desingularized boundary-integral method. Calculation of 2D streamlines within planes of symmetry reveals the internal equilibria of the flow. The type of each equilibrium is classified in 3D and their interactions probed using passive tracers and their Poincaré maps. For the two-capsule droplet, saddle points located on orthogonal symmetry planes influence the regular flow within the drop. For the three-sphere droplet, large regions of chaos are observed, embedded with simple periodic orbits. Flow is visualized via passive dyes, using material lines and surfaces. In 2D, solely the interface between two passive interior fluids is advected using an adaptive number of linked tracer particles. The reduction in dimension decreases the number of required tracer points, and also resolves arbitrarily thin filaments, in contrast to backward cell-mapping methods. In 3D, the advection of a material surface, bounded by the droplet interface, is enabled using an adaptive mesh scheme. Off-lattice 3D contour advection allows for highly resolved visualizations of the internal flow and quantification of the associated degree of mixing. Analysis of the time-dependent growth of material surfaces and 3D mixing numbers suggests the three-sphere droplet exhibits superior mixing properties compared to the two-capsule droplet.}, } @article {pmid34005876, year = {2021}, author = {Brahmachary, S and Natarajan, G and Kulkarni, V and Sahoo, N and Ashok, V and Kumar, V}, title = {Role of solution reconstruction in hypersonic viscous computations using a sharp interface immersed boundary method.}, journal = {Physical review. E}, volume = {103}, number = {4-1}, pages = {043302}, doi = {10.1103/PhysRevE.103.043302}, pmid = {34005876}, issn = {2470-0053}, abstract = {This work discusses the development of a sharp interface immersed boundary (IB) method for viscous compressible flows and its assessment for accurate computations of wall shear and heat fluxes in hypersonic flows. The IB method is implemented in an unstructured Cartesian finite-volume (FV) framework and resolves the geometric interface sharply on the nonconformal mesh through direct imposition of boundary conditions employing a local reconstruction approach. The efficacy of the IB-FV solver is investigated for canonical high-speed viscous flows over a range of Mach numbers. The numerical results indicate that the surface pressure and shear stress distributions are computed with reasonable accuracy, whereas surface heat fluxes for aerodynamically blunt configurations are underpredicted. Employing a set of carefully designed experiments and simple diagnostic tools, we probe the possible causes for the underprediction in heat flux. We show that there exist two sources of error-one due to grid resolution and the other due to solution reconstruction, with the latter being more prominent and responsible for the observed underprediction in heat fluxes. Studies reveal that the heat flux estimates are sensitive to the choice of temperature reconstruction and linear interpolations could lead to poor estimates of heat flux. Our investigations conclusively point out the fact that existing polynomial-based reconstruction approaches for sharp interface IB techniques are not necessarily adequate for heat transfer predictions in high Reynolds number hypersonic flows.}, } @article {pmid34001882, year = {2021}, author = {Nguyen, QM and Abouezzi, J and Ristroph, L}, title = {Early turbulence and pulsatile flows enhance diodicity of Tesla's macrofluidic valve.}, journal = {Nature communications}, volume = {12}, number = {1}, pages = {2884}, pmid = {34001882}, issn = {2041-1723}, abstract = {Microfluidics has enabled a revolution in the manipulation of small volumes of fluids. Controlling flows at larger scales and faster rates, or macrofluidics, has broad applications but involves the unique complexities of inertial flow physics. We show how such effects are exploited in a device proposed by Nikola Tesla that acts as a diode or valve whose asymmetric internal geometry leads to direction-dependent fluidic resistance. Systematic tests for steady forcing conditions reveal that diodicity turns on abruptly at Reynolds number [Formula: see text] and is accompanied by nonlinear pressure-flux scaling and flow instabilities, suggesting a laminar-to-turbulent transition that is triggered at unusually low [Formula: see text]. To assess performance for unsteady forcing, we devise a circuit that functions as an AC-to-DC converter, rectifier, or pump in which diodes transform imposed oscillations into directed flow. Our results confirm Tesla's conjecture that diodic performance is boosted for pulsatile flows. The connections between diodicity, early turbulence and pulsatility uncovered here can inform applications in fluidic mixing and pumping.}, } @article {pmid33998932, year = {2021}, author = {Chen, X and Zhang, Y and Wang, J}, title = {Simulation analysis of mixing in passive microchannel with fractal obstacles based on Murray's law.}, journal = {Computer methods in biomechanics and biomedical engineering}, volume = {24}, number = {15}, pages = {1670-1678}, doi = {10.1080/10255842.2021.1906867}, pmid = {33998932}, issn = {1476-8259}, mesh = {Computer Simulation ; Diffusion ; *Fractals ; }, abstract = {In this paper, we designed fractal obstacles according to Murray's law and set them in a microchannel. We study the influence of the numbers of fractal obstacles, channel widths, branch widths, and the distance between fractal obstacles on mixing efficiency. The optimized micromixer has a high mixing efficiency of more than 90% at all velocities. This paper focuses on the analysis of the variation of mixing efficiency and pressure drop in the range of Reynolds number (Re) 0.1-150. The simulation results show that when the fluid velocity is low, the mixing efficiency of the fluids is mainly improved by molecular diffusion, when the fluid velocity is high, the microchannel with fractal obstacles can promote chaotic convection of the fluids and improve the mixing efficiency. The fractal structure based on Murray's law can be widely used in the design of passive micromixer.}, } @article {pmid33998624, year = {2021}, author = {Su, J and Chen, X and Zhu, Y and Hu, G}, title = {Machine learning assisted fast prediction of inertial lift in microchannels.}, journal = {Lab on a chip}, volume = {21}, number = {13}, pages = {2544-2556}, doi = {10.1039/d1lc00225b}, pmid = {33998624}, issn = {1473-0189}, mesh = {Cross-Sectional Studies ; Lab-On-A-Chip Devices ; Machine Learning ; *Microfluidic Analytical Techniques ; Microfluidics ; }, abstract = {Inertial effect has been extensively used in manipulating both engineered particles and biocolloids in microfluidic platforms. The design of inertial microfluidic devices largely relies on precise prediction of particle migration that is determined by the inertial lift acting on the particle. In spite of being the only means to accurately obtain the lift forces, direct numerical simulation (DNS) often consumes high computational cost and even becomes impractical when applied to microchannels with complex geometries. Herein, we proposed a fast numerical algorithm in conjunction with machine learning techniques for the analysis and design of inertial microfluidic devices. A database of inertial lift forces was first generated by conducting DNS over a wide range of operating parameters in straight microchannels with three types of cross-sectional shapes, including rectangular, triangular and semicircular shapes. A machine learning assisted model was then developed to gain the inertial lift distribution, by simply specifying the cross-sectional shape, Reynolds number and particle blockage ratio. The resultant inertial lift was integrated into the Lagrangian tracking method to quickly predict the particle trajectories in two types of microchannels in practical devices and yield good agreement with experimental observations. Our database and the associated codes allow researchers to expedite the development of the inertial microfluidic devices for particle manipulation.}, } @article {pmid33997904, year = {2021}, author = {Garayev, K and Murphy, DW}, title = {Metachronal Swimming of Mantis Shrimp: Kinematics and Interpleopod Vortex Interactions.}, journal = {Integrative and comparative biology}, volume = {61}, number = {5}, pages = {1631-1643}, doi = {10.1093/icb/icab052}, pmid = {33997904}, issn = {1557-7023}, mesh = {Animals ; Biomechanical Phenomena ; *Copepoda ; *Decapoda ; Extremities ; Models, Biological ; Swimming ; }, abstract = {Mantis shrimp swim via metachronal rowing, a pattern in which the pleopods (swimming limbs) stroke sequentially, starting with the last pair and followed by anterior neighbors. A similar swimming pattern is used at various sizes, Reynolds numbers, and advance ratios by diverse organisms including ciliates, ctenophores, copepods, krill, and lobsters. Understanding this type of locomotion is important because it is widespread and may inspire the design of underwater vehicles where efficiency, robustness, and maneuverability are desired. However, detailed measurements of the flow around free-swimming, metachronally rowing organisms are scarce, especially for organisms swimming in a high Reynolds number regime (Re ≥ 104). In this study, we present time-resolved, planar PIV measurements of a swimming peacock mantis shrimp (Odontodactylus scyllarus). Simultaneous kinematics measurements of the animal, which had body and pleopod lengths of 114 and 20 mm, respectively, reveal mean swimming speeds of 0.2-1.9 m s-1 and pleopod beat frequencies of 3.6-13 Hz, corresponding to advance ratios of 0.75-1.84 and body-based Reynolds numbers of 23,000-217,000. Further, the animal's stroke is not purely metachronal, with a long phase lag between initiation of the first and fifth pleopod power strokes. Flow measurements in the sagittal plane show that each stroking pleopod pair creates a posteriorly moving tip vortex which evades destruction by the recovery strokes of other pleopod pairs. The vortex created by the anteriormost pleopod pair is the strongest and, owing to the animal's high advance ratio, is intercepted by the power stroke of the posteriormost pleopod pair. The vortex strength increases as a result of this interaction, which may increase swimming speed or efficiency. A relationship for vortex interception by the posterior pleopod is proposed that relates the phase lag between the interacting pleopods to the beat frequency, distance between those pleopods, and speed of the vortex relative to the animal. We describe this interaction with a novel parameter called the interpleopod vortex phase matching Strouhal number StIVPM which is equal to the phase lag between interacting pleopods. This new nondimensional parameter may be useful in predicting the conditions where a constructive interaction may occur in other species or in physical models. Finally, we relate the advance ratio to the Reynolds number ratio, the ratio between the body-based Reynolds number and the pleopod-based Reynolds number. The importance of these parameters in promoting the interpleopod vortex interactions identified here, in dynamically scaled experiments, and in wake signatures behind schooling metachronal swimmers is discussed.}, } @article {pmid33986400, year = {2021}, author = {Mehboudi, A and Yeom, J}, title = {A passive Stokes flow rectifier for Newtonian fluids.}, journal = {Scientific reports}, volume = {11}, number = {1}, pages = {10182}, pmid = {33986400}, issn = {2045-2322}, abstract = {Non-linear effects of the Navier-Stokes equations disappear under the Stokes regime of Newtonian fluid flows disallowing a flow rectification behavior. Here we show that passive flow rectification of Newtonian fluids is obtainable under the Stokes regime of both compressible and incompressible flows by introducing nonlinearity into the otherwise linear Stokes equations. Asymmetric flow resistances arise in shallow nozzle/diffuser microchannels with deformable ceiling, in which the fluid flow is governed by a non-linear coupled fluid-solid mechanics equation. The proposed model captures the unequal deflection profile of the deformable ceiling depending on the flow direction under the identical applied pressure, permitting a larger flow rate in the nozzle configuration. Ultra-low aspect ratio microchannels sealed by a flexible membrane have been fabricated to demonstrate passive flow rectification for low-Reynolds-number flows (0.001 < Re < 10) of common Newtonian fluids such as water, methanol, and isopropyl alcohol. The proposed rectification mechanism is also extended to compressible flows, leading to the first demonstration of rectifying equilibrium gas flows under the Stokes flow regime. While the maximum rectification ratio experimentally obtained in this work is limited to 1.41, a higher value up to 1.76 can be achieved by optimizing the width profile of the asymmetric microchannels.}, } @article {pmid33976300, year = {2021}, author = {Kazemi, A and Castillo, L and Curet, OM}, title = {Mangrove roots model suggest an optimal porosity to prevent erosion.}, journal = {Scientific reports}, volume = {11}, number = {1}, pages = {9969}, pmid = {33976300}, issn = {2045-2322}, abstract = {Mangrove swamps are extremely productive ecosystems providing many ecological services in coastal regions. The hydrodynamic interactions of mangrove roots and water flow have been proposed as a key element to mitigate erosion. Several studies reveal that precise prediction of the morphological evolution of coastal areas, in the face of global warming and the consequent sea-level rise, requires an understanding of interactions between root porosity (the fraction of the volume of void space over the total volume), water flows, and sediment transport. Water flows around the mangrove prop roots create a complex energetic process that mixes up sediments and generates a depositional region posterior to the roots. In this work, we investigated the boundary layer behind permeable arrays of cylinders (patch) that represent the mangrove roots to explore the impact of patch porosity on the onset of sediment transport. The flow measurements were performed in a vertical plane along the water depth downstream of the mangrove root models. A high-resolution Particle Image Velocimetry (PIV) was used in a flume to observe the impact of porosity on the mean flow, velocity derivatives, skin friction coefficient, and production of turbulent kinetic energy for Reynolds number of 2500 (based on patch diameter length-scale). Here, we proposed a predictive model for critical velocity for incipient motion that takes into account the mangrove roots porosity and the near-bed turbulence effect. It is found that the patch with the [Formula: see text] porosity, has the maximum critical velocity over which the sediment transport initiates. We found the optimum porosity has the minimum sediment erosion and creates negative vorticity sources near the bed that increases the critical velocity. This signifies an optimum porosity for the onset of sediment transport consistent with the porosity of mangroves in nature. The phenomenological model is elucidated based on an analysis of the vorticity evolution equation for viscous incompressible flows. For the optimum porous patch, a sink of vorticity was formed which yielded to lower the near-bed turbulence and vorticity. The minimum velocity fluctuations were sufficient to initiate the boundary layer transition, however, the viscous dissipation dominated the turbulence production to obstruct the sediment transport. This work identified the pivotal role of mangrove root porosity in sediment transport in terms of velocity and its derivatives in wall-bounded flows. Our work also provides insight into the sediment transport and erosion processes that govern the evolution of the shapes of shorelines.}, } @article {pmid33956314, year = {2021}, author = {Vasilopoulos, K and Lekakis, I and Sarris, IE and Tsoutsanis, P}, title = {Large eddy simulation of dispersion of hazardous materials released from a fire accident around a cubical building.}, journal = {Environmental science and pollution research international}, volume = {28}, number = {36}, pages = {50363-50377}, pmid = {33956314}, issn = {1614-7499}, mesh = {Accidents ; *Air Pollutants/analysis ; *Hazardous Substances ; Models, Theoretical ; Wind ; }, abstract = {The turbulent smoke dispersion from a pool fire around a cubical building is studied using large eddy simulation at a high Reynolds number, corresponding to existing experimental measurements both in laboratory and field test scales. Emphasis of this work is on the smoke dispersion due to two different fuel pool fire accident scenarios, initiated behind the building. For the setup of fire in the first case, crude oil was used with a heat release rate of 7.8 MW, and in the second, diesel oil with a heat release rate of 13.5 MW. It is found that in both fire scenarios, the downstream extent of the toxic zone is approximately the same. This is explained in terms of the fact that the smoke concentration and dispersion are influenced mainly by the convective buoyant forces and the strong turbulence mixing processes within the wake zone of the building. It is suggested that wind is the dominating factor in these accident scenarios, which represent the conditions resulting in the highest toxicity levels.}, } @article {pmid33953255, year = {2021}, author = {Asai, T and Hong, S}, title = {Aerodynamics of the newly approved football for the English Premier League 2020-21 season.}, journal = {Scientific reports}, volume = {11}, number = {1}, pages = {9578}, pmid = {33953255}, issn = {2045-2322}, abstract = {Footballs are typically constructed with 32 panels. Recently, the number of panels has been successively reduced to 14, 8, and 6 panels, and official balls have been adopted with complex panel shapes and aerodynamics that differ from those of 32-panel balls. The official ball for the 2020-21 season of the English Premier League comprises just four panels with a complex panel shape and surface groove design; however, its aerodynamics have not yet been clarified. This study aims to clarify the aerodynamic characteristics (drag, side force, lift force, their deviations, and critical Reynolds number) of the new 4-panel ball (Flight 2020, Nike) in comparison to a 6-panel ball (Tsubasa 2020, Adidas) and conventional 32-panel ball (Pelada 2020, Molten) using a wind tunnel test, surface design measurement, and a simple 2D flight simulation. The results showed that Flight 2020 has greater surface roughness and smaller critical Reynolds number than Pelada 2020 and Tsubasa 2020, resulting to its marginally greater drag force in the supercritical region, and slightly smaller fluctuations of the side and lift forces. Furthermore, Flight with a symmetrical orientation exhibits a significantly higher drag coefficient in the supercritical region, suggesting its greater air resistance during flight under this condition.}, } @article {pmid33949106, year = {2021}, author = {Sharan, P and Nsamela, A and Lesher-Pérez, SC and Simmchen, J}, title = {Microfluidics for Microswimmers: Engineering Novel Swimmers and Constructing Swimming Lanes on the Microscale, a Tutorial Review.}, journal = {Small (Weinheim an der Bergstrasse, Germany)}, volume = {17}, number = {26}, pages = {e2007403}, doi = {10.1002/smll.202007403}, pmid = {33949106}, issn = {1613-6829}, mesh = {Engineering ; *Microfluidics ; *Swimming ; }, abstract = {This paper provides an updated review of recent advances in microfluidics applied to artificial and biohybrid microswimmers. Sharing the common regime of low Reynolds number, the two fields have been brought together to take advantage of the fluid characteristics at the microscale, benefitting microswimmer research multifold. First, microfluidics offer simple and relatively low-cost devices for high-fidelity production of microswimmers made of organic and inorganic materials in a variety of shapes and sizes. Microscale confinement and the corresponding fluid properties have demonstrated differential microswimmer behaviors in microchannels or in the presence of various types of physical or chemical stimuli. Custom environments to study these behaviors have been designed in large part with the help of microfluidics. Evaluating microswimmers in increasingly complex lab environments such as microfluidic systems can ensure more effective implementation for in-field applications. The benefits of microfluidics for the fabrication and evaluation of microswimmers are balanced by the potential use of microswimmers for sample manipulation and processing in microfluidic systems, a large obstacle in diagnostic and other testing platforms. In this review various ways in which these two complementary technology fields will enhance microswimmer development and implementation in various fields are introduced.}, } @article {pmid33947812, year = {2021}, author = {Hartl, B and Hübl, M and Kahl, G and Zöttl, A}, title = {Microswimmers learning chemotaxis with genetic algorithms.}, journal = {Proceedings of the National Academy of Sciences of the United States of America}, volume = {118}, number = {19}, pages = {}, pmid = {33947812}, issn = {1091-6490}, mesh = {Algorithms ; Animals ; Caenorhabditis elegans/physiology ; Chemotaxis/*genetics/*physiology ; Computer Simulation ; Flagella/physiology ; Learning/*physiology ; Machine Learning ; Models, Biological ; Motion ; Neural Networks, Computer ; Swimming/*physiology ; }, abstract = {Various microorganisms and some mammalian cells are able to swim in viscous fluids by performing nonreciprocal body deformations, such as rotating attached flagella or by distorting their entire body. In order to perform chemotaxis (i.e., to move toward and to stay at high concentrations of nutrients), they adapt their swimming gaits in a nontrivial manner. Here, we propose a computational model, which features autonomous shape adaptation of microswimmers moving in one dimension toward high field concentrations. As an internal decision-making machinery, we use artificial neural networks, which control the motion of the microswimmer. We present two methods to measure chemical gradients, spatial and temporal sensing, as known for swimming mammalian cells and bacteria, respectively. Using the genetic algorithm NeuroEvolution of Augmenting Topologies, surprisingly simple neural networks evolve. These networks control the shape deformations of the microswimmers and allow them to navigate in static and complex time-dependent chemical environments. By introducing noisy signal transmission in the neural network, the well-known biased run-and-tumble motion emerges. Our work demonstrates that the evolution of a simple and interpretable internal decision-making machinery coupled to the environment allows navigation in diverse chemical landscapes. These findings are of relevance for intracellular biochemical sensing mechanisms of single cells or for the simple nervous system of small multicellular organisms such as Caenorhabditis elegans.}, } @article {pmid33938005, year = {2021}, author = {Wang, S and Liu, Z and Wu, S and Sun, H and Zeng, W and Wei, J and Fan, Z and Sui, Z and Liu, L and Pan, X}, title = {Microalgae separation by inertia-enhanced pinched flow fractionation.}, journal = {Electrophoresis}, volume = {42}, number = {21-22}, pages = {2223-2229}, doi = {10.1002/elps.202000325}, pmid = {33938005}, issn = {1522-2683}, mesh = {Chemical Fractionation ; Chlorella ; *Microalgae ; Ships ; Water ; }, abstract = {To improve the accuracy and efficiency of ships' ballast water detection, the separation of microalgae according to size is significant. In this article, a method to separate microalgae based on inertia-enhanced pinched flow fractionation (iPFF) was reported. The method utilized the inertial lift force induced by flow to separate microalgae according to size continuously. The experimental results show that, as the Reynolds number increases, the separation effect becomes better at first, but then stays unchanged. The best separation effect can be obtained when the Reynolds number is 12.3. In addition, with the increase of the flow rate ratio between sheath fluid and microalgae mixture, the separation effect becomes better and the best separation effect can be obtained when the flow rate ratio reaches 10. In this case, the recovery rate of Tetraselmis sp. is about 90%, and the purity is about 86%; the recovery rate of Chlorella sp. is as high as 99%, and the purity is about 99%. After that, the separation effect keeps getting better but very slowly. In general, this study provides a simple method for the separation of microalgae with different sizes, and lays a foundation for the accurate detection of microalgae in the ballast water.}, } @article {pmid33924044, year = {2021}, author = {Rao, Y and Li, L and Wang, S and Zhao, S and Zhou, S}, title = {Numerical Simulation Study on Flow Laws and Heat Transfer of Gas Hydrate in the Spiral Flow Pipeline with Long Twisted Band.}, journal = {Entropy (Basel, Switzerland)}, volume = {23}, number = {4}, pages = {}, doi = {10.3390/e23040489}, pmid = {33924044}, issn = {1099-4300}, support = {51574045//National Nature Science Foundation of China/ ; 51974037//National Nature Science Foundation of China/ ; 2020D-5007-0211//CNPC Innovation Foundation/ ; CJ20200085//Changzhou Applied Basic Research Project/ ; }, abstract = {The natural gas hydrate plugging problems in the mixed pipeline are becoming more and more serious. The hydrate plugging has gradually become an important problem to ensure the safety of pipeline operation. The deposition and heat transfer characteristics of natural gas hydrate particles in the spiral flow pipeline have been studied. The DPM model (discrete phase model) was used to simulate the motion of solid particles, which was used to simulate the complex spiral flow characteristics of hydrate in the pipeline with a long twisted band. The deposition and heat transfer characteristics of gas hydrate particles in the spiral flow pipeline were studied. The velocity distribution, pressure drop distribution, heat transfer characteristics, and particle settling characteristics in the pipeline were investigated. The numerical results showed that compared with the straight flow without a long twisted band, two obvious eddies are formed in the flow field with a long twisted band, and the velocities are maximum at the center of the vortices. Along the direction of the pipeline, the two vortices move toward the pipe wall from near the twisted band, which can effectively carry the hydrate particles deposited on the wall. With the same Reynolds number, the twisted rate was greater, the spiral strength was weaker, the tangential velocity was smaller, and the pressure drop was smaller. Therefore, the pressure loss can be reduced as much as possible with effect of the spiral flow. In a straight light flow, the Nusselt number is in a parabolic shape with the opening downwards. At the center of the pipe, the Nusselt number gradually decreased toward the pipe wall at the maximum, and at the near wall, the attenuation gradient of the Nu number was large. For spiral flow, the curve presented by the Nusselt number was a trough at the center of the pipe and a peak at 1/2 of the pipe diameter. With the reduction of twist rate, the Nusselt number becomes larger. Therefore, the spiral flow can make the temperature distribution more even and prevent the large temperature difference, resulting in the mass formation of hydrate particles in the pipeline wall. Spiral flow has a good carrying effect. Under the same condition, the spiral flow carried hydrate particles at a distance about 3-4 times farther than that of the straight flow.}, } @article {pmid33923993, year = {2021}, author = {Yuan, S and Jiang, B and Peng, T and Li, Q and Zhou, M}, title = {An Investigation of Flow Patterns and Mixing Characteristics in a Cross-Shaped Micromixer within the Laminar Regime.}, journal = {Micromachines}, volume = {12}, number = {4}, pages = {}, pmid = {33923993}, issn = {2072-666X}, support = {51920105008//National Natural Science Foundation of China/ ; 2019SK2221//Key Research and Development Program of Hunan Province of China/ ; }, abstract = {A fast mixing is critical for subsequent practical development of microfluidic devices, which are often used for assays in the detection of reagents and samples. The present work sets up computational fluid dynamics simulations to explore the flow characteristic and mixing mechanism of fluids in cross-shaped mixers within the laminar regime. First, the effects of increasing an operating parameter on local mixing quality along the microchannels are investigated. It is found that sufficient diffusion cannot occur even though the concentration gradient is large at a high Reynolds number. Meanwhile, a method for calculating local mixing efficiency is also characterized. The mixing efficiency varies exponentially with the flow distance. Second, in order to optimize the cross-shaped mixer, the effects of design parameters, namely aspect ratio, mixing angle and blockage, on mixing quality are captured and the visualization of velocity and concentration distribution are demonstrated. The results show that the aspect ratio and the blockage play an important role in accelerating the mixing process. They can improve the mixing efficiency by increasing the mass transfer area and enhancing the chaotic advection, respectively. In contrast, the inflow angle that affects dispersion length is not an effective parameter. Besides, the surface roughness, which makes the disturbance of fluid flow by roughness more obvious, is considered. Three types of rough elements bring benefits for enhancing mixing quality due to the convection induced by the lateral velocity.}, } @article {pmid33922337, year = {2021}, author = {Ansari, A and Kavousi, S and Helfer, F and Millar, G and Thiel, DV}, title = {An Improved Modelling Approach for the Comprehensive Study of Direct Contact Membrane Distillation.}, journal = {Membranes}, volume = {11}, number = {5}, pages = {}, pmid = {33922337}, issn = {2077-0375}, abstract = {Direct Contact Membrane Distillation (DCMD) is a promising and feasible technology for water desalination. Most of the models used to simulate DCMD are one-dimensional and/or use a linear function of vapour pressure which relies on experimentally determined parameters. In this study, the model of DCMD using Nusselt correlations was improved by coupling the continuity, momentum, and energy equations to better capture the downstream alteration of flow field properties. A logarithmic function of vapour pressure, which is independent from experiments, was used. This allowed us to analyse DCMD with different membrane properties. The results of our developed model were in good agreement with the DCMD experimental results, with less than 7% deviation. System performance metrics, including water flux, temperature, and concentration polarisation coefficient and thermal efficiency, were analysed by varying inlet feed and permeate temperature, inlet velocity, inlet feed concentration, channel length. In addition, twenty-two commercial membranes were analysed to obtain a real vision on the influence of membrane characteristics on system performance metrics. The results showed that the feed temperature had the most significant effect on water flux and thermal efficiency. The increased feed temperature enhanced the water flux and thermal efficiency; however, it caused more concentration and temperature polarisation. On the other hand, the increased inlet velocity was found to provide increased water flux and reduced temperature and concertation polarisation as well. It was also found that the membrane properties, especially thickness and porosity, can affect the DCMD performance significantly. A two-fold increase of feed temperature increased the water flux and thermal efficiency, 10-fold and 27%, respectively; however, it caused an increase in temperature and concertation polarisation, at 48% and 34%, respectively. By increasing Reynolds number from 80 to 1600, the water flux, CPC, and TPC enhanced by 2.3-fold, 2%, and 21%, respectively. The increased feed concentration from 0 to 250 [g/L] caused a 26% reduction in water flux. To capture the downstream alteration of flow properties, it was shown that the ratio of inlet value to outlet value of system performance metrics decreased significantly throughout the module. Therefore, improvement over the conventional model is undeniable, as the new model can assist in achieving optimal operation conditions.}, } @article {pmid33922099, year = {2021}, author = {Yuan, C and Zhang, H and Li, X and Oishi, M and Oshima, M and Yao, Q and Li, F}, title = {Numerical Investigation of T-Shaped Microfluidic Oscillator with Viscoelastic Fluid.}, journal = {Micromachines}, volume = {12}, number = {5}, pages = {}, pmid = {33922099}, issn = {2072-666X}, support = {51776057, 51606054, 51911540073 and 11972384//National Natural Science Foundation of China/ ; }, abstract = {Oscillatory flow has many applications in micro-scaled devices. The methods of realizing microfluidic oscillators reported so far are typically based on the impinging-jet and Coanda effect, which usually require the flow Reynolds number to be at least at the order of unity. Another approach is to introduce elastomeric membrane into the microfluidic units; however, the manufacturing process is relatively complex, and the membrane will become soft after long-time operation, which leads to deviation from the design condition. From the perspective of the core requirement of a microfluidic circuit, i.e., nonlinearity, the oscillatory microfluidic flow can be realized via the nonlinear characteristics of viscoelastic fluid flow. In this paper, the flow characteristics of viscoelastic fluid (Boger-type) in a T-shaped channel and its modified structures are studied by two-dimensional direct numerical simulation (DNS). The main results obtained from the DNS study are as follows: (1) Both Weissenberg (Wi) number and viscosity ratio need to be within a certain range to achieve a periodic oscillating performance; (2) With the presence of the dynamic evolution of the pair of vortices in the upstream near the intersection, the oscillation intensity increases as the elasticity-dominated area in the junction enlarges; (3) Considering the simplicity of the T-type channel as a potential oscillator, the improved structure should have a groove carved toward the entrance near the upper wall. The maximum oscillation intensity measured by the standard deviation of flow rate at outlet is increased by 129% compared with that of the original standard T-shaped channel under the same condition. To sum up, with Wi number and viscosity ratio within a certain range, the regular periodic oscillation characteristics of Oldroyd-B type viscoelastic fluid flow in standard T-shaped and its modified channels can be obtained. This structure can serve as a passive microfluidic oscillator with great potential value at an extremely low Reynolds number, which has the advantages of simplicity, no moving parts and fan-out of two.}, } @article {pmid33920267, year = {2021}, author = {Abbasnezhad, N and Kebdani, M and Shirinbayan, M and Champmartin, S and Tcharkhtchi, A and Kouidri, S and Bakir, F}, title = {Development of a Model Based on Physical Mechanisms for the Explanation of Drug Release: Application to Diclofenac Release from Polyurethane Films.}, journal = {Polymers}, volume = {13}, number = {8}, pages = {}, pmid = {33920267}, issn = {2073-4360}, support = {9 bis, Avenue Iéna 75783 PARIS Cedex 16 France//Foundation Arts et Métiers/ ; }, abstract = {In this study, we present a method for prediction of the drug-release profile based on the physical mechanisms that can intervene in drug release from a drug-carrier. The application presented here incorporates the effects of drug concentration and Reynolds number defining the circulating flow in the testing vein. The experimental data used relate to the release of diclofenac from samples of non-degradable polyurethane subjected to static and continuous flow. This case includes simultaneously three mechanisms: burst-release, diffusion and osmotic pressure, identified beforehand here as being able to contribute to the drug liberation. For this purpose, authors coded the Sequential Quadratic Programming Algorithm to solve the problem of non-linear optimization. The experimental data used to develop the mathematical model obtained from release studies carried out in water solution at 37 °C, for three concentrations of diclofenac and two water flow rates. We discuss the contribution of mechanisms and kinetics by considering two aforementioned parameters and, following that, we obtain the specific-model and compare the calculated results with the experimental results for the reserved cases. The results showed that drug percentage mostly affect the burst release, however flow rate has affected the osmotic release. In addition, release kinetics of all the mechanisms have increased by increasing the values of two considered parameters.}, } @article {pmid33917762, year = {2021}, author = {Wang, R and Duan, R and Jia, H}, title = {Experimental Validation of Falling Liquid Film Models: Velocity Assumption and Velocity Field Comparison.}, journal = {Polymers}, volume = {13}, number = {8}, pages = {}, pmid = {33917762}, issn = {2073-4360}, support = {Grant No. 51779126//National Natural Science Foundation of China/ ; }, abstract = {This publication focuses on the experimental validation of film models by comparing constructed and experimental velocity fields based on model and elementary experimental data. The film experiment covers Kapitza numbers Ka = 278.8 and Ka = 4538.6, a Reynolds number range of 1.6-52, and disturbance frequencies of 0, 2, 5, and 7 Hz. Compared to previous publications, the applied methodology has boundary identification procedures that are more refined and provide additional adaptive particle image velocimetry (PIV) method access to synthetic particle images. The experimental method was validated with a comparison with experimental particle image velocimetry and planar laser induced fluorescence (PIV/PLIF) results, Nusselt's theoretical prediction, and experimental particle tracking velocimetry (PTV) results of flat steady cases, and a good continuity equation reproduction of transient cases proves the method's fidelity. The velocity fields are reconstructed based on different film flow model velocity profile assumptions such as experimental film thickness, flow rates, and their derivatives, providing a validation method of film model by comparison between reconstructed velocity experimental data and experimental velocity data. The comparison results show that the first-order weighted residual model (WRM) and regularized model (RM) are very similar, although they may fail to predict the velocity field in rapidly changing zones such as the front of the main hump and the first capillary wave troughs.}, } @article {pmid33915686, year = {2021}, author = {Rasool, G and Shafiq, A and Alqarni, MS and Wakif, A and Khan, I and Bhutta, MS}, title = {Numerical Scrutinization of Darcy-Forchheimer Relation in Convective Magnetohydrodynamic Nanofluid Flow Bounded by Nonlinear Stretching Surface in the Perspective of Heat and Mass Transfer.}, journal = {Micromachines}, volume = {12}, number = {4}, pages = {}, pmid = {33915686}, issn = {2072-666X}, abstract = {The aim of this research is mainly concerned with the numerical examination of Darcy-Forchheimer relation in convective magnetohydrodynamic nanofluid flow bounded by non-linear stretching sheet. A visco-elastic and strictly incompressible liquid saturates the designated porous medium under the direct influence of the Darcy-Forchheimer model and convective boundary. The magnetic effect is taken uniformly normal to the flow direction. However, the model is bounded to a tiny magnetic Reynolds number for practical applications. Boundary layer formulations are taken into consideration. The so-formulated leading problems are converted into highly nonlinear ordinary problems using effectively modified transformations. The numerical scheme is applied to solve the governing problems. The outcomes stipulate that thermal layer receives significant modification in the incremental direction for augmented values of thermal radiation parameter Rd. Elevation in thermal Biot number γ1 apparently results a significant rise in thermal layer and associated boundary layer thickness. The solute Biot number is found to be an enhancing factor the concentration profile. Besides the three main profiles, the contour and density graphs are sketched for both the linear and non-linear cases. Furthermore, skin friction jumps for larger porosity and larger Forchheimer number. Both the heat and mass flux numbers receive a reduction for augmented values of the Forchheimer number. Heat flux enhances, while mass flux reduces, the strong effect of thermal Biot number. The considered problem could be helpful in any several industrial and engineering procedures, such as rolling, polymeric extrusion, continuously stretching done in plastic thin films, crystal growth, fiber production, and metallic extrusion, etc.}, } @article {pmid33905256, year = {2021}, author = {Sasaki, K and Okue, T and Nakai, T and Uchida, Y and Nishiyama, N}, title = {Lateral Growth of Uniformly Thin Gold Nanosheets Facilitated by Two-Dimensional Precursor Supply.}, journal = {Langmuir : the ACS journal of surfaces and colloids}, volume = {37}, number = {19}, pages = {5872-5877}, doi = {10.1021/acs.langmuir.1c00344}, pmid = {33905256}, issn = {1520-5827}, abstract = {The nanosheets of highly symmetric materials with a face-centered cubic lattice such as gold have been synthesized by adsorbing the precursors on a flat surface, whose chemical specificity induces the anisotropy of growth rates. We have succeeded in the fabrication of gold nanosheets in a hydrophilic space inside highly separated bilayers, which work as two-dimensional hydrophilic reactors, in a hyperswollen lamellar liquid crystalline phase of an amphiphile solution. One of the physical properties, amphiphilicity, confines the ingredients therein. The nanosheets can only grow in the in-plane direction due to the inhibition of the out-of-plane growth rather than the anisotropy of growth rates probably. Thus, the synthesis can be accelerated; the particles can be completed within 15 min. As not relying on chemical specificity, silver nanosheets could also be synthesized in the same way. The suspension of gold and silver nanosheets without any amphiphiles could be obtained, and the solvent is replaceable. We found that the width of the obtained gold nanosheets is proportional to the Reynolds number of the solution because the area of the bilayer in the hyperswollen lamellar phase depends on shear stress. This implies that the areas of gold nanosheets depend on the areas of the bilayers, and it can be controlled by changing the Reynolds number. This method could be widely used to continuously obtain large-area nanosheets of various materials in a roll-to-roll manufacturing process.}, } @article {pmid33902681, year = {2021}, author = {Heyland, A and Roszell, J and Chau, J and Chai, K and Eaton, A and Nolan, K and Madden, K and Ahmed, WH}, title = {Mass transfer and flow characterization of novel algae-based nutrient removal system.}, journal = {Biotechnology for biofuels}, volume = {14}, number = {1}, pages = {104}, pmid = {33902681}, issn = {1754-6834}, support = {Seeding Food Innovation Grant//George Weston Foundation/ ; }, abstract = {BACKGROUND: Recirculating aquaculture systems (RAS) are an essential component of sustainable inland seafood production. Still, nutrient removal from these systems can result in substantial environmental problems, or present a major cost factor with few added value options. In this study, an innovative and energy-efficient algae based nutrient removal system (NRS) was developed that has the potential to generate revenue through algal commercialization. We optimized mass transfer in our NRS design using novel aeration and mixing technology, using air lift pumps and developed an original membrane cartridge for the continuous operation of nutrient removal and algae production. Specifically, we designed, manufactured and tested a 60-L NRS prototype. Based on specific airlift mixing conditions as well as concentration gradients, we assessed NRS nutrient removal capacity. We then examined the effects of different internal bioreactor geometries and radial orientations on the mixing efficiency.

RESULTS: Using the start-up dynamic method, the overall mass transfer coefficient was found to be in the range of 0.00164-0.0074 [Formula: see text], depending on flow parameters and we confirmed a scaling relationship of mass transfer across concentration gradients. We found the optimal Reynolds number to be 500 for optimal mass transfer, as higher Reynolds numbers resulted in a relatively reduced increase of mass transfer. This relationship between mass transfer and Reynolds number is critical to assess scalability of our system. Our results demonstrate an even distribution of dissolved oxygen levels across the reactor core, demonstrating adequate mixing by the airlift pump, a critical consideration for optimal algal growth. Distribution of dissolved gases in the reactor was further assessed using flow visualization in order to relate the bubble distribution to the mass transfer capabilities of the reactor. We run a successful proof of principle trial using the green alga Dunaliella tertiolecta to assess mass transfer of nutrients across the membrane and biomass production.

CONCLUSIONS: Manipulation of the concentration gradient across the membrane demonstrates a more prominent role of airlift mixing at higher concentration gradients. Specifically, the mass transfer rate increased threefold when the concentration gradient was increased 2.5-fold. We found that we can grow algae in the reactor chamber at rates comparable to those of other production systems and that the membrane scaffolds effectively remove nutrients form the wastewater. Our findings provide support for scalability of the design and support the use of this novel NRS for nutrient removal in aquaculture and potentially other applications.}, } @article {pmid33895456, year = {2021}, author = {Song, Z and Tong, J and Pfleging, W and Sun, J}, title = {A review: Learning from the flight of beetles.}, journal = {Computers in biology and medicine}, volume = {133}, number = {}, pages = {104397}, doi = {10.1016/j.compbiomed.2021.104397}, pmid = {33895456}, issn = {1879-0534}, mesh = {Animals ; Biomechanical Phenomena ; *Coleoptera ; Mechanical Phenomena ; Miniaturization ; Wings, Animal ; }, abstract = {Some Coleoptera (popularly referred to as beetles) can fly at a low Reynolds number with their deployable hind wings, which directly enables a low body weight-a good bioinspiration strategy for miniaturization of micro-air vehicles (MAVs). The hind wing is a significant part of the body and has a folding/unfolding mechanism whose unique function benefits from different structures and materials. This review summarizes the actions, factors, and mechanisms of beetle flight and bioinspired MAVs with deployable wings. The elytron controlled by muscles is the protected part for the folded hind wing and influences flight performance. The resilin, the storage material for elasticity, is located in the folding parts. The hind wings' folding/unfolding mechanism and flight performance can be influenced by vein structures of hollow, solid and wrinkled veins, the hemolymph that flows in hollow veins and its hydraulic mechanism, and various mechanical properties of veins. The action of beetle flight includes flapping flight, hovering, gliding, and landing. The hind wing is passively deformed through force and hemolymph, and the attack angle of the hind wing and the nanomechanics of the veins, muscles and mass body determine the flight performance. Based these factors, bioinspired MAVs with a new deployable wing structure and new materials will be designed to be much more effective and miniaturized. The new fuels and energy supply are significant aspects of MAVs.}, } @article {pmid33889684, year = {2021}, author = {Sadeq, AM and Ahmed, SF and Sleiti, AK}, title = {Dataset for transient 3D simulations of turbulent premixed flames of Gas-to-Liquid (GTL) fuel.}, journal = {Data in brief}, volume = {36}, number = {}, pages = {106956}, doi = {10.1016/j.dib.2021.106956}, pmid = {33889684}, issn = {2352-3409}, abstract = {A fan-stirred combustion vessel is used to study the premixed turbulent combustion of diesel, Gas to Liquids (GTL) and 50/50 diesel-GTL and to generate these datasets. A numerical simulation approach is implemented for modelling the premixed combustion of the three fuels under different thermodynamics and turbulence initial conditions, using Zimont Turbulent Flame Speed Closure (Zimont TFC) model. Different parameters are obtained from these simulation runs such as turbulent eddy viscosity (µ), turbulent kinetic energy (k), Damkohler number (Da), Reynolds number (ReT) and turbulent flame speed (St). The raw, filtered and pre-processed data are imported from ANSYS Fluent and then listed on filtered tables for the ease of accessibility. These datasets can be then used to perform research in different related areas such as chemical kinetic mechanisms, ignition delay time, flame ignition mechanisms and flame extinction and diffusion. Also, they can be employed to further understand trends, patterns, and anomalies in data. In addition, they can be compared with other numerical models to establish a robust knowledge about the modelling of premixed turbulent combustion. For more information and discussion of the dataset creation, the reader is directed to the full-length article, "Abdellatif M. Sadeq, Samer F. Ahmed, Ahmad K. Sleiti, Transient 3D simulations of turbulent premixed flames of gas-to-liquid (GTL) fuel in a fan-stirred combustion vessel, Fuel, Volume 291, 2021, 120,184, ISSN 0016 2361, https://doi.org/10.1016/j.fuel.2021.120184" [1].}, } @article {pmid33871634, year = {2021}, author = {Lamont, EI and Emlet, RB}, title = {Swimming Kinematics of Cyprids of the Barnacle Balanus glandula.}, journal = {Integrative and comparative biology}, volume = {61}, number = {5}, pages = {1567-1578}, doi = {10.1093/icb/icab028}, pmid = {33871634}, issn = {1557-7023}, mesh = {Animals ; Biomechanical Phenomena ; *Copepoda ; Larva ; Swimming ; *Thoracica ; }, abstract = {Larvae of barnacles typically pass through naupliar and cyprid planktonic stages before settlement and metamorphosis. As the final larval stage, cyprids swim much faster than nauplii and in turbulent fluid environments with high shears as they seek habitat. Cyprids swim with six pairs of reciprocating thoracic appendages and use two anterior antennules during settlement. Our understanding of how thoracic appendages generate movement is limited due to short stroke intervals (∼5 ms) that impede observations of the shape and trajectory of appendages. Here, we used high-speed videography to observe both free-swimming and tethered cyprids of the intertidal acorn barnacle Balanus glandula to produce a comprehensive description of thoracic appendage swimming kinematics. Cyprids used a drag-based method of swimming: their six pairs of thoracic appendages moved through metachronal power strokes and synchronous recovery strokes similar to the thoracopod motions in calanoid copepods during escape swimming. During the power stroke, plumose setae on each appendage pair spread laterally into a high surface area and high drag paddle composed of a meshwork of fused setules. This interconnected setal array collapsed into a low surface area and low drag shape during the recovery stroke. These effective swimming appendages allowed cyprids to move upward at an average speed of 1.4 cm/s (∼25 body lengths/s) with an average beat frequency of 16 beats/s, and reach an instantaneous velocity of up to 6 cm/s. Beat frequency of the thoracic appendages was significantly associated with speed, with higher beat frequencies indicating faster swimming speed. At their average speed, cyprids moved at the intermediate Reynolds number of ∼10, in which both viscous and inertial forces affected movement. Cyprids could alter swimming direction by sweeping the posterior-most appendage pair to one side and beating the remaining thoracic appendages synchronously through the power stroke with greater motion on the outside of their turn. These results greatly enhance our understanding both of cyprid motility and how small planktonic organisms can use swimming appendages with fused setule arrays to reach high swimming speeds and affect directional changes.}, } @article {pmid33870835, year = {2021}, author = {Si, XA and Talaat, M and Su, WC and Xi, J}, title = {Inhalation dosimetry of nasally inhaled respiratory aerosols in the human respiratory tract with locally remodeled conducting lungs.}, journal = {Inhalation toxicology}, volume = {33}, number = {4}, pages = {143-159}, doi = {10.1080/08958378.2021.1912860}, pmid = {33870835}, issn = {1091-7691}, mesh = {*Administration, Inhalation ; Aerosols/*administration & dosage ; *Airway Remodeling ; Dose-Response Relationship, Drug ; Humans ; Lung/anatomy & histology/pathology ; Models, Biological ; Nanoparticles/*administration & dosage ; Nose/anatomy & histology ; }, abstract = {Objective: Respiratory diseases are often accompanied by alterations to airway morphology. However, inhalation dosimetry data in remodeled airways are scarce due to the challenges in reconstructing diseased respiratory morphologies. This study aims to study the airway remodeling effects on the inhalation dosimetry of nasally inhaled nanoparticles in a nose-lung geometry that extends to G9 (ninth generation).Materials and methods: Statistical shape modeling was used to develop four diseased lung models with varying levels of bronchiolar dilation/constriction in the left-lower (LL) lobe (i.e. M1-M4). Respiratory airflow and particle deposition were simulated using a low Reynolds number k-ω turbulence model and a Lagrangian tracking approach.Results: Significant discrepancies were observed in the flow partitions between the left and right lungs, as well as between the lower and upper lobes of the left lung, which changed by 10-fold between the most dilated and constricted models.Much lower doses were predicted on the surface of the constricted LL bronchioles G4-G9, as well as into the peripheral airways beyond G9 of the LL lung. However, the LL lobar remodeling had little effect on the dosimetry in the nasopharynx, as well as on the total dosimetry in the nose-lung geometry (up to G9).Conclusion: It is suggested that airway remodeling may pose a higher viral infection risk to the host by redistributing the inhaled viruses to healthy lung lobes. Airway remodeling effects should also be considered in the treatment planning of inhalation therapies, not only because of the dosimetry variation from altered lung morphology but also its evolution as the disease progresses.}, } @article {pmid33863724, year = {2021}, author = {Trkulja, CL and Jungholm, O and Davidson, M and Jardemark, K and Marcus, MM and Hägglund, J and Karlsson, A and Karlsson, R and Bruton, J and Ivarsson, N and Srinivasa, SP and Cavallin, A and Svensson, P and Jeffries, GDM and Christakopoulou, MN and Reymer, A and Ashok, A and Willman, G and Papadia, D and Johnsson, E and Orwar, O}, title = {Rational antibody design for undruggable targets using kinetically controlled biomolecular probes.}, journal = {Science advances}, volume = {7}, number = {16}, pages = {}, pmid = {33863724}, issn = {2375-2548}, mesh = {*Antibodies, Monoclonal/chemistry ; *Antigens ; Binding Sites, Antibody ; Epitopes ; Humans ; }, abstract = {Several important drug targets, e.g., ion channels and G protein-coupled receptors, are extremely difficult to approach with current antibody technologies. To address these targets classes, we explored kinetically controlled proteases as structural dynamics-sensitive druggability probes in native-state and disease-relevant proteins. By using low-Reynolds number flows, such that a single or a few protease incisions are made, we could identify antibody binding sites (epitopes) that were translated into short-sequence antigens for antibody production. We obtained molecular-level information of the epitope-paratope region and could produce high-affinity antibodies with programmed pharmacological function against difficult-to-drug targets. We demonstrate the first stimulus-selective monoclonal antibodies targeting the transient receptor potential vanilloid 1 (TRPV1) channel, a clinically validated pain target widely considered undruggable with antibodies, and apoptosis-inducing antibodies selectively mediating cytotoxicity in KRAS-mutated cells. It is our hope that this platform will widen the scope of antibody therapeutics for the benefit of patients.}, } @article {pmid33862704, year = {2021}, author = {Fouxon, I and Feinberg, J and Käpylä, P and Mond, M}, title = {Reynolds number dependence of Lyapunov exponents of turbulence and fluid particles.}, journal = {Physical review. E}, volume = {103}, number = {3-1}, pages = {033110}, doi = {10.1103/PhysRevE.103.033110}, pmid = {33862704}, issn = {2470-0053}, abstract = {The Navier-Stokes equations generate an infinite set of generalized Lyapunov exponents defined by different ways of measuring the distance between exponentially diverging perturbed and unperturbed solutions. This set is demonstrated to be similar, yet different, from the generalized Lyapunov exponent that provides moments of distance between two fluid particles below the Kolmogorov scale. We derive rigorous upper bounds on dimensionless Lyapunov exponent of the fluid particles that demonstrate the exponent's decay with Reynolds number Re in accord with previous studies. In contrast, terms of cumulant series for exponents of the moments have power-law growth with Re. We demonstrate as an application that the growth of small fluctuations of magnetic field in ideal conducting turbulence is hyperintermittent, being exponential in both time and Reynolds number. We resolve the existing contradiction between the theory, that predicts slow decrease of dimensionless Lyapunov exponent of turbulence with Re, and observations exhibiting quite fast growth. We demonstrate that it is highly plausible that a pointwise limit for the growth of small perturbations of the Navier-Stokes equations exists.}, } @article {pmid33854256, year = {2021}, author = {Waringer, J and Vitecek, S and Martini, J and Zittra, C and Handschuh, S and Vieira, A and Kuhlmann, HC}, title = {Hydraulic niche utilization by larvae of the three Drusinae clades (Insecta: Trichoptera).}, journal = {Biologia}, volume = {76}, number = {5}, pages = {1465-1473}, pmid = {33854256}, issn = {0006-3088}, support = {P 31258/FWF_/Austrian Science Fund FWF/Austria ; }, abstract = {Hydraulic niche descriptors of final instar larvae of nine Drusus species (Trichoptera) were studied in small, spring-fed, first-order headwaters located in the Mühlviertel (Upper Austria), Koralpe (Carinthia, Austria), and in the Austrian and Italian Alps. The species investigated covered all three clades of Drusinae: the shredder clade (Drusus franzi, D. alpinus), the grazer clade (D. biguttatus, D. chauvinianus, D. dudor, D. monticola), and the filtering carnivore clade (D. chrysotus, D. katagelastos, D. muelleri). Flow velocity was measured at front center of 68 larvae, head upstream, on the top of mineral substrate particles at water depths of 10-30 mm, using a tripod-stabilized Micro propeller meter (propeller diameter = 10 mm). Each data series consisted of a sampled measurement lasting 30 s (measuring interval = 1 s). In total, 2040 single velocity measurements were taken. Instantaneous flow velocities and drag at the sites of the 68 larvae varied from 0 to 0.93 m s-1 and 0 to 8346 *10-6 N, respectively. Flow velocities and drag between the three clades were highly significantly different (p < 0.001); mean velocity (± 95% confidence limits) for the three clades were 0.09 ± 0.00 m s-1 for the shredder, 0.25 ± 0.00 m s-1 for the grazer, and 0.31 ± 0.01ms-1 for the filtering carnivore clade; the corresponding data for drag were (85 ± 18)*10-6 N, (422 ± 61)*10-6 N and (1125 ± 83)*10-6 N, respectively. Adhesive friction ranged from (41.07 ± 53.03)*10-6 N in D. franzi to (255.24 ± 216.87)*10-6 N in D. chrysotus. Except in D. franzi and D. dudor adhesive friction was always well below drag force, indicating that submerged weight alone was not sufficient to stabilize the larvae in their hydraulic environment. Reynolds numbers varied between 0 in D. franzi and D. alpinus, and 12,634 in D. katagelastos, with 7% of the total in the laminar (R < 500), 30%in the transitional (R = 500-2000), and 61%in the fully turbulent stage (R > 2000). Froude numbers (Fr) varied from 0 to 2.97. The two Drusus species of the shredder clade and three out of four species of the grazer clade were exposed to subcritical Fr < 1, one species of the grazer clade and two out of three species of the filtering clade to supercritical Froude numbers >1.}, } @article {pmid33853049, year = {2021}, author = {Wang, Q and Wu, H}, title = {Mathematical modeling of chemotaxis guided amoeboid cell swimming.}, journal = {Physical biology}, volume = {18}, number = {4}, pages = {}, doi = {10.1088/1478-3975/abf7d8}, pmid = {33853049}, issn = {1478-3975}, support = {S10 OD016290/OD/NIH HHS/United States ; }, mesh = {*Chemotaxis ; Computational Biology ; Dictyostelium/*physiology ; Models, Biological ; Swimming/physiology ; }, abstract = {Cells and microorganisms adopt various strategies to migrate in response to different environmental stimuli. To date, many modeling research has focused on the crawling-basedDictyostelium discoideum(Dd) cells migration induced by chemotaxis, yet recent experimental results reveal that even without adhesion or contact to a substrate, Dd cells can still swim to follow chemoattractant signals. In this paper, we develop a modeling framework to investigate the chemotaxis induced amoeboid cell swimming dynamics. A minimal swimming system consists of one deformable Dd amoeboid cell and a dilute suspension of bacteria, and the bacteria produce chemoattractant signals that attract the Dd cell. We use themathematical amoeba modelto generate Dd cell deformation and solve the resulting low Reynolds number flows, and use a moving mesh based finite volume method to solve the reaction-diffusion-convection equation. Using the computational model, we show that chemotaxis guides a swimming Dd cell to follow and catch bacteria, while on the other hand, bacterial rheotaxis may help the bacteria to escape from the predator Dd cell.}, } @article {pmid33834308, year = {2021}, author = {Solovev, A and Friedrich, BM}, title = {Lagrangian mechanics of active systems.}, journal = {The European physical journal. E, Soft matter}, volume = {44}, number = {4}, pages = {49}, pmid = {33834308}, issn = {1292-895X}, abstract = {We present a multi-scale modeling and simulation framework for low-Reynolds number hydrodynamics of shape-changing immersed objects, e.g., biological microswimmers and active surfaces. The key idea is to consider principal shape changes as generalized coordinates and define conjugate generalized hydrodynamic friction forces. Conveniently, the corresponding generalized friction coefficients can be pre-computed and subsequently reused to solve dynamic equations of motion fast. This framework extends Lagrangian mechanics of dissipative systems to active surfaces and active microswimmers, whose shape dynamics is driven by internal forces. As an application case, we predict in-phase and anti-phase synchronization in pairs of cilia for an experimentally measured cilia beat pattern.}, } @article {pmid33833251, year = {2021}, author = {Abdal, S and Hussain, S and Siddique, I and Ahmadian, A and Ferrara, M}, title = {On solution existence of MHD Casson nanofluid transportation across an extending cylinder through porous media and evaluation of priori bounds.}, journal = {Scientific reports}, volume = {11}, number = {1}, pages = {7799}, pmid = {33833251}, issn = {2045-2322}, abstract = {It is a theoretical exportation for mass transpiration and thermal transportation of Casson nanofluid over an extending cylindrical surface. The Stagnation point flow through porous matrix is influenced by magnetic field of uniform strength. Appropriate similarity functions are availed to yield the transmuted system of leading differential equations. Existence for the solution of momentum equation is proved for various values of Casson parameter [Formula: see text], magnetic parameter M, porosity parameter [Formula: see text] and Reynolds number Re in two situations of mass transpiration (suction/injuction). The core interest for this study aroused to address some analytical aspects. Therefore, existence of solution is proved and uniqueness of this results is discussed with evaluation of bounds for existence of solution. Results for skin friction factor are established to attain accuracy for large injection values. Thermal and concentration profiles are delineated numerically by applying Runge-Kutta method and shooting technique. The flow speed retards against M, [Formula: see text] and [Formula: see text] for both situations of mass injection and suction. The thermal boundary layer improves with Brownian and thermopherotic diffusions.}, } @article {pmid33809995, year = {2021}, author = {Abramowicz-Gerigk, T and Burciu, Z and Jachowski, J and Kreft, O and Majewski, D and Stachurska, B and Sulisz, W and Szmytkiewicz, P}, title = {Experimental Method for the Measurements and Numerical Investigations of Force Generated on the Rotating Cylinder under Water Flow.}, journal = {Sensors (Basel, Switzerland)}, volume = {21}, number = {6}, pages = {}, doi = {10.3390/s21062216}, pmid = {33809995}, issn = {1424-8220}, support = {WN/2020/PZ/01 and WN/2020/PZ/03//Gdynia Maritime University/ ; }, abstract = {The paper presents the experimental test setup and measurement method of hydrodynamic force generated on the rotating cylinder (rotor) under uniform flow including the free surface effect. The experimental test setup was a unique construction installed in the flume tank equipped with advanced flow generating and measuring systems. The test setup consisted of a bearing mounted platform with rotor drive and sensors measuring the hydrodynamic force. The low length to diameter ratio cylinders were selected as models of bow rotor rudders of a shallow draft river barge. The rotor dynamics was tested for the rotational speeds up to 550 rpm and water current velocity up to 0.85 m/s. The low aspect ratio of the cylinder and free surface effect had significant impacts on the phenomena influencing the generated hydrodynamic force. The effects of the rotor length to diameter ratio, rotational velocity to flow velocity ratio, and the Reynolds number on the lift force were analyzed. The validation of the computational model against experimental results is presented. The results show a similar trend of results for the simulation and experiment.}, } @article {pmid33808487, year = {2021}, author = {Okuducu, MB and Aral, MM}, title = {Toward the Next Generation of Passive Micromixers: A Novel 3-D Design Approach.}, journal = {Micromachines}, volume = {12}, number = {4}, pages = {}, pmid = {33808487}, issn = {2072-666X}, abstract = {Passive micromixers are miniaturized instruments that are used to mix fluids in microfluidic systems. In microchannels, combination of laminar flows and small diffusion constants of mixing liquids produce a difficult mixing environment. In particular, in very low Reynolds number flows, e.g., Re < 10, diffusive mixing cannot be promoted unless a large interfacial area is formed between the fluids to be mixed. Therefore, the mixing distance increases substantially due to a slow diffusion process that governs fluid mixing. In this article, a novel 3-D passive micromixer design is developed to improve fluid mixing over a short distance. Computational Fluid Dynamics (CFD) simulations are used to investigate the performance of the micromixer numerically. The circular-shaped fluid overlapping (CSFO) micromixer design proposed is examined in several fluid flow, diffusivity, and injection conditions. The outcomes show that the CSFO geometry develops a large interfacial area between the fluid bodies. Thus, fluid mixing is accelerated in vertical and/or horizontal directions depending on the injection type applied. For the smallest molecular diffusion constant tested, the CSFO micromixer design provides more than 90% mixing efficiency in a distance between 260 and 470 µm. The maximum pressure drop in the micromixer is found to be less than 1.4 kPa in the highest flow conditioned examined.}, } @article {pmid33807063, year = {2021}, author = {Rudl, J and Hanzelmann, C and Feja, S and Meyer, A and Potthoff, A and Buschmann, MH}, title = {Laminar Pipe Flow with Mixed Convection under the Influence of Magnetic Field.}, journal = {Nanomaterials (Basel, Switzerland)}, volume = {11}, number = {3}, pages = {}, doi = {10.3390/nano11030824}, pmid = {33807063}, issn = {2079-4991}, support = {49VF180041//Bundesministerium für Wirtschaft und Energie/ ; }, abstract = {Magnetic influence on ferronanofluid flow is gaining increasing interest from not only the scientific community but also industry. The aim of this study is the examination of the potentials of magnetic forces to control heat transfer. Experiments are conducted to investigate the interaction between four different configurations of permanent magnets and laminar pipe flow with mixed convection. For that purpose a pipe flow test rig is operated with a water-magnetite ferronanofluid. The Reynolds number is varied over one order of magnitude (120-1200). To characterise this suspension, density, solid content, viscosity, thermal conductivity, and specific heat capacity are measured. It is found that, depending on the positioning of the magnet(s) and the Reynolds number, heat transfer is either increased or decreased. The experiments indicate that this is a local effect. After relaxation lengths ranging between 2 and 3.5 lengths of a magnet, all changes disappeared. The conclusion from these findings is that magnetic forces are rather a tool to control heat transfer locally than to enhance the overall heat transfer of heat exchangers or the like. Magnetically caused disturbances decay due to viscous dissipation and the flow approaches the basic state again.}, } @article {pmid33800534, year = {2021}, author = {Naas, TT and Hossain, S and Aslam, M and Rahman, A and Hoque, ASM and Kim, KY and Islam, SMR}, title = {Kinematic Measurements of Novel Chaotic Micromixers to Enhance Mixing Performances at Low Reynolds Numbers: Comparative Study.}, journal = {Micromachines}, volume = {12}, number = {4}, pages = {}, pmid = {33800534}, issn = {2072-666X}, abstract = {In this work, a comparative investigation of chaotic flow behavior inside multi-layer crossing channels was numerically carried out to select suitable micromixers. New micromixers were proposed and compared with an efficient passive mixer called a Two-Layer Crossing Channel Micromixer (TLCCM), which was investigated recently. The computational evaluation was a concern to the mixing enhancement and kinematic measurements, such as vorticity, deformation, stretching, and folding rates for various low Reynolds number regimes. The 3D continuity, momentum, and species transport equations were solved by a Fluent ANSYS CFD code. For various cases of fluid regimes (0.1 to 25 values of Reynolds number), the new configuration displayed a mixing enhancement of 40%-60% relative to that obtained in the older TLCCM in terms of kinematic measurement, which was studied recently. The results revealed that all proposed micromixers have a strong secondary flow, which significantly enhances the fluid kinematic performances at low Reynolds numbers. The visualization of mass fraction and path-lines presents that the TLCCM configuration is inefficient at low Reynolds numbers, while the new designs exhibit rapid mixing with lower pressure losses. Thus, it can be used to enhance the homogenization in several microfluidic systems.}, } @article {pmid33800140, year = {2021}, author = {De Bartolo, S and Vittorio, M and Francone, A and Guido, F and Leone, E and Mastronardi, VM and Notaro, A and Tomasicchio, GR}, title = {Direct Scaling of Measure on Vortex Shedding through a Flapping Flag Device in the Open Channel around a Cylinder at Re∼103: Taylor's Law Approach.}, journal = {Sensors (Basel, Switzerland)}, volume = {21}, number = {5}, pages = {}, pmid = {33800140}, issn = {1424-8220}, abstract = {The problem of vortex shedding, which occurs when an obstacle is placed in a regular flow, is governed by Reynolds and Strouhal numbers, known by dimensional analysis. The present work aims to propose a thin films-based device, consisting of an elastic piezoelectric flapping flag clamped at one end, in order to determine the frequency of vortex shedding downstream an obstacle for a flow field at Reynolds number Re∼103 in the open channel. For these values, Strouhal number obtained in such way is in accordance with the results known in literature. Moreover, the development of the voltage over time, generated by the flapping flag under the load due to flow field, shows a highly fluctuating behavior and satisfies Taylor's law, observed in several complex systems. This provided useful information about the flow field through the constitutive law of the device.}, } @article {pmid33794172, year = {2021}, author = {Chen, WH and Mutuku, JK and Yang, ZW and Hwang, CJ and Lee, WJ and Ashokkumar, V}, title = {An investigation for airflow and deposition of PM2.5 contaminated with SAR-CoV-2 virus in healthy and diseased human airway.}, journal = {Environmental research}, volume = {197}, number = {}, pages = {111096}, doi = {10.1016/j.envres.2021.111096}, pmid = {33794172}, issn = {1096-0953}, mesh = {*Asthma ; Computer Simulation ; Humans ; Italy ; *Lung ; Mexico ; Models, Biological ; Particulate Matter/toxicity ; }, abstract = {This study is motivated by the amplified transmission rates of the SAR-CoV-2 virus in areas with high concentrations of fine particulates (PM2.5) as reported in northern Italy and Mexico. To develop a deeper understanding of the contribution of PM2.5 in the propagation of the SAR-CoV-2 virus in the population, the deposition patterns and efficiencies (DEs) of PM2.5 laced with the virus in healthy and asthmatic airways are studied. Physiologically correct 3-D models for generations 10-12 of the human airways are applied to carry out a numerical analysis of two-phase flow for full breathing cycles. Two concentrations of PM2.5 are applied for the simulation, i.e., 30 μg⋅m-3 and 80 μg⋅m-3 for three breathing statuses, i.e., rest, light exercise, and moderate activity. All the PM2.5 injected into the control volume is assumed to be 100% contaminated with the SAR-CoV-2 virus. Skewed air-flow phenomena at the bifurcations are proportional to the Reynolds number at the inlet, and their intensity in the asthmatic airway exceeded that of the healthy one. Upon exhalation, two peak air-flow vectors from daughter branches combine to form one big vector in the parent generation. Asthmatic airway models has higher deposition efficiencies (DEs) for contaminated PM2.5 as compared to the healthy one. Higher DEs arise in the asthmatic airway model due to complex secondary flows which increase the impaction of contaminated PM2.5 on airways' walls.}, } @article {pmid33768184, year = {2021}, author = {Edomwonyi-Otu, LC and Dosumu, AI and Yusuf, N}, title = {Effect of oil on the performance of biopolymers as drag reducers in fresh water flow.}, journal = {Heliyon}, volume = {7}, number = {3}, pages = {e06535}, doi = {10.1016/j.heliyon.2021.e06535}, pmid = {33768184}, issn = {2405-8440}, abstract = {This study looks at the effectiveness of natural polymers (biopolymers) as drag reducers in flows of oil-water mixtures. The technique of using drag reducers to minimize the frictional drag in pipeline transportation of fluids is getting more challenging and there is need to be more environmentally friendly by using natural polymers. In this report, two natural polymers: xanthan gum (XG) and guar gum (GG), were used as drag reducers in a 12-mm ID straight conduit with water. The concentration of the gums was varied from 50 to 250 pm while 25, 0.50 and 0.75 fractions of oil were mixed with freshwater. The molecular weight of the gums was also determined to gain insight into their influence on the rheology of the fluids. The result showed that the gums (natural polymers) performed better as drag reducer in freshwater than in mixture with oil. Specifically, the drag reduction (DR) of 200 pm GG and XG solutions at Reynolds number of 59000 in freshwater was 39% and 44% respectively, while with the addition of 50% oil fraction, it was reduced to 19% and 32% respectively. DR reduced with oil fraction. It was concluded that XG performs better in the presence of oil than GG.}, } @article {pmid33767256, year = {2021}, author = {Wang, L and Ni, P and Xi, G}, title = {The effect of off-center placement of twisted tape on flow and heat transfer characteristics in a circular tube.}, journal = {Scientific reports}, volume = {11}, number = {1}, pages = {6844}, pmid = {33767256}, issn = {2045-2322}, abstract = {This study is conducted to investigate the effect of off-center placement of twisted tape on flow distribution and heat transfer in a circular tube. The effect of tape width of 20, 18, 16, 14 and 12 mm on the heat transfer performance is discussed under the same twist ratio of 2.0. The numerical analysis of the flow field, average Nusselt number, friction factor and thermo-hydraulic performance parameter of the tube are discussed with Reynolds number ranged from 2600 to 8760. The results indicate that the Nusselt number of the tube fitted with center-placed twisted tapes at various width is 7-51% higher than the plain tube, and performance in low Reynolds region was found more effective than that in high Reynolds region. The heat transfer for circular tube with twisted tape attached to the wall shows better performance than that for the tube with center-placed twisted tape. With a smaller tape width, a higher increasing ratio of Nu-wall/Nu-center is obtained. The increasing ratio for Nusselt number ranged from 3 to 18%. However, the use of twisted tape inserts is not beneficial for energy saving. The thermo-hydraulic performance parameters for convective heat transfer of helium gas flowing in a circular tube are below unity for the calculated Reynolds region.}, } @article {pmid33766315, year = {2021}, author = {Wang, X and Liu, Z and Cai, Y and Wang, B and Luo, X}, title = {A cost-effective serpentine micromixer utilizing ellipse curve.}, journal = {Analytica chimica acta}, volume = {1155}, number = {}, pages = {338355}, doi = {10.1016/j.aca.2021.338355}, pmid = {33766315}, issn = {1873-4324}, abstract = {Due to high mixing performance and simple geometry structure, serpentine micromixer is one typical passive micromixer that has been widely investigated. Traditional zigzag and square-wave serpentine micromixers can achieve sufficient mixing, but tend to induce significant pressure drop. The excessive pressure drop means more energy consumption, which leads to low cost-performance of mixing. To mitigate excessive pressure drop, a novel serpentine micromixer utilizing ellipse curve is proposed. While fluids flowing through ellipse curve microchannels, the flow directions keep continuous changing. Therefore, the Dean vortices are induced throughout the whole flow path. Numerical simulation and visualization experiments are conducted at Reynolds number (Re) ranging from 0.1 to 100. Dean vortices varies with the changing curvature in different ellipse curves, and local Dean numbers are calculated for quantitative evaluation. The results suggest that the ellipse with a larger eccentricity induces stronger Dean vortices, thus better mixing performance can be obtained. A parameter, named mixing performance cost (Mec), is proposed to evaluate the cost-performance of micromixers. Compared with the zigzag, square-wave and other improved serpentine micromixers, the ellipse curve micromixer produces lower pressure drop while have the capability to maintain excellent mixing performance. The ellipse curve micromixer is proved to be more cost-effective for rapid mixing in complex microfluidic systems.}, } @article {pmid33765646, year = {2021}, author = {Ghosh, UU and Ali, H and Ghosh, R and Kumar, A}, title = {Bacterial streamers as colloidal systems: Five grand challenges.}, journal = {Journal of colloid and interface science}, volume = {594}, number = {}, pages = {265-278}, doi = {10.1016/j.jcis.2021.02.102}, pmid = {33765646}, issn = {1095-7103}, mesh = {*Bacteria ; *Biofilms ; Hydrodynamics ; Rivers ; }, abstract = {Bacteria can thrive in biofilms, which are intricately organized communities with cells encased in a self-secreted matrix of extracellular polymeric substances (EPS). Imposed hydrodynamic stresses can transform this active colloidal dispersion of bacteria and EPS into slender thread-like entities called streamers. In this perspective article, the reader is introduced to the world of such deformable 'bacteria-EPS' composites that are a subclass of the generic flow-induced colloidal structures. While bacterial streamers have been shown to form in a variety of hydrodynamic conditions (turbulent and creeping flows), its abiotic analogues have only been demonstrated in low Reynolds number (Re < 1) particle-laden polymeric flows. Streamers are relevant to a variety of situations ranging from natural formations in caves and river beds to clogging of biomedical devices and filtration membranes. A critical review of the relevant biophysical aspects of streamer formation phenomena and unique attributes of its material behavior are distilled to unveil five grand scientific challenges. The coupling between colloidal hydrodynamics, device geometry and streamer formation are highlighted.}, } @article {pmid33759003, year = {2021}, author = {Mohammadinejad, S and Faivre, D and Klumpp, S}, title = {Stokesian dynamics simulations of a magnetotactic bacterium.}, journal = {The European physical journal. E, Soft matter}, volume = {44}, number = {3}, pages = {40}, pmid = {33759003}, issn = {1292-895X}, mesh = {*Bacteria ; Chemotaxis ; *Magnetic Fields ; *Models, Biological ; }, abstract = {The swimming of bacteria provides insight into propulsion and steering under the conditions of low-Reynolds number hydrodynamics. Here we address the magnetically steered swimming of magnetotactic bacteria. We use Stokesian dynamics simulations to study the swimming of single-flagellated magnetotactic bacteria (MTB) in an external magnetic field. Our model MTB consists of a spherical cell body equipped with a magnetic dipole moment and a helical flagellum rotated by a rotary motor. The elasticity of the flagellum as well as magnetic and hydrodynamic interactions is taken into account in this model. We characterized how the swimming velocity is dependent on parameters of the model. We then studied the U-turn motion after a field reversal and found two regimes for weak and strong fields and, correspondingly, two characteristic time scales. In the two regimes, the U-turn time is dominated by the turning of the cell body and its magnetic moment or the turning of the flagellum, respectively. In the regime for weak fields, where turning is dominated by the magnetic relaxation, the U-turn time is approximately in agreement with a theoretical model based on torque balance. In the strong-field regime, strong deformations of the flagellum are observed. We further simulated the swimming of a bacterium with a magnetic moment that is inclined relative to the flagellar axis. This scenario leads to intriguing double helical trajectories that we characterize as functions of the magnetic moment inclination and the magnetic field. For small inclination angles ([Formula: see text]) and typical field strengths, the inclination of the magnetic moment has only a minor effect on the swimming of MTB in an external magnetic field. Large inclination angles result in a strong reduction in the velocity in direction of the magnetic field, consistent with recent observations that bacteria with large inclination angles use a different propulsion mechanism.}, } @article {pmid33756187, year = {2021}, author = {Jamil, DF and Saleem, S and Roslan, R and Al-Mubaddel, FS and Rahimi-Gorji, M and Issakhov, A and Din, SU}, title = {Analysis of non-Newtonian magnetic Casson blood flow in an inclined stenosed artery using Caputo-Fabrizio fractional derivatives.}, journal = {Computer methods and programs in biomedicine}, volume = {203}, number = {}, pages = {106044}, doi = {10.1016/j.cmpb.2021.106044}, pmid = {33756187}, issn = {1872-7565}, mesh = {Arteries ; *Atherosclerosis ; Blood Flow Velocity ; Constriction, Pathologic ; Hemodynamics ; Humans ; *Models, Cardiovascular ; }, abstract = {BACKGROUND AND OBJECTIVE: Arterial diseases would lead to several serious disorders in the cardiovascular system such as atherosclerosis. These disorders are mainly caused by the presence of fatty deposits, cholesterol and lipoproteins inside blood vessel. This paper deals with the analysis of non-Newtonian magnetic blood flow in an inclined stenosed artery.

METHODS: The Casson fluid was used to model the blood that flows under the influences of uniformly distributed magnetic field and oscillating pressure gradient. The governing fractional differential equations were expressed using the Caputo Fabrizio fractional derivative without singular kernel.

RESULTS: The analytical solutions of velocities for non-Newtonian model were then calculated by means of Laplace and finite Hankel transforms. These velocities were then presented graphically. The result shows that the velocity increases with respect to Reynolds number and Casson parameter, while decreases when Hartmann number increases.

CONCLUSIONS: Casson blood was treated as the non-Newtonian fluid. The MHD blood flow was accelerated by pressure gradient. These findings are beneficial for studying atherosclerosis therapy, the diagnosis and therapeutic treatment of some medical problems.}, } @article {pmid33754747, year = {2021}, author = {Mouzourides, P and Kyprianou, A and Neophytou, MK}, title = {Exploring the multi-fractal nature of the air flow and pollutant dispersion in a turbulent urban atmosphere and its implications for long range pollutant transport.}, journal = {Chaos (Woodbury, N.Y.)}, volume = {31}, number = {1}, pages = {013110}, doi = {10.1063/1.5123918}, pmid = {33754747}, issn = {1089-7682}, abstract = {This work investigates the multi-fractal nature of a turbulent urban atmosphere using high-resolution atmospheric data. Meteorological and concentration measurements of passive and reactive pollutants collected over a 3-year period in a sub-urban high-Reynolds number atmospheric field were analyzed. Scaling laws characterizing the self-similarity and thereby depicting the multi-fractal nature are determined by calculating the singularity spectra, where a range of Hölder exponents, h, are estimated. In doing so, the complexity of the urban atmosphere entailing different stability regimes was addressed. Using the Monin-Obukhov length (LMO) as a marker of atmospheric stability and thereby an indication of the magnitude of anisotropy, we find where and how self-similarity is manifested relative to the different regimes and we estimate corresponding appropriate scaling laws. We find that the wind speed obeys the -5/3 law suggested by Kolmogorov only when the atmosphere lies within the stable regime as defined by Monin-Obukhov theory. Specifically, when the ratio of the atmospheric boundary layer height (Hb.l) over LMO is greater than 15, and at the same time, the ratio of the height above ground of the wind measurements (z0) over LMO is higher than 3 (i.e., in stable regime), then the singularity spectra of wind speed time series indicate that the dominant Hölder exponent, hmax, coincides with Kolmogorov's second hypothesis. On the contrary under unstable regimes in the atmosphere where the anisotropy is approached, different scaling laws are estimated. In detail, when z0/LMO<0, the dominant Hölder exponent, hmax, of the singularity spectra of the wind speed time series is either negative or close to zero, which is an indication of an impulse-like singularity, that is associated with rapid changes. For the ambient temperature and air quality measurements such as of carbon monoxide and particulate matter concentrations, it was found that they obey different laws, which are related with the long-term correlation of their data fluctuation.}, } @article {pmid33754568, year = {2021}, author = {Ji, JY and Zhao, YG and Yang, K and Zhang, WT and Gao, LQ and Ming, J and Wang, SS}, title = {Effects of the distribution of biological soil crust on the hydrodynamic characteristics of surface runoff.}, journal = {Ying yong sheng tai xue bao = The journal of applied ecology}, volume = {32}, number = {3}, pages = {1015-1022}, doi = {10.13287/j.1001-9332.202103.017}, pmid = {33754568}, issn = {1001-9332}, mesh = {Geologic Sediments ; Hydrodynamics ; *Rain ; *Soil ; }, abstract = {The distribution pattern of biological soil crusts (biocrusts) is one of the main factors affecting runoff and sediment yield. The relationship between runoff and sediment yield and biocrusts' distribution pattern is not clear, which hinders understanding the mechanism underlying the effects of biocrusts on runoff and sediment from slopes. To fill the knowledge gap, we investigated the relationship between the landscape indices of three biocrusts' distribution patterns, i.e. zonation, chessboard and random, and the hydraulic parameters, using of simulated rainfall experiments and landscape ecology methods. The results showed that biocrust significantly affected the erosion force of slopes and that its distribution pattern could affect slope erosion dynamics. Compared to bare soil, the presence of biocrusts significantly reduced the runoff velocity (54.6%) and Froude number (67.0%), increased the runoff depth (86.2%) and Darcy-Weisbach resistance coefficient (10.68 times), but did not affect the Reynolds number and runoff power. Expect for the runoff depth, there were significant differences in the hydraulic parameters of the three biocrusts' distribution patterns, with the random pattern having the strongest impacts on the dynamics of slope erosion. Based on factor analysis and cluster analysis, five indices of percentage of patch to landscape area, patch density, landscape shape index, patch cohesion and splitting could be used as the indicators for the distribution characteristics of biocrust patches. The patch cohesion and splitting of biocrust patches were the main distribution pattern indices of the hydrodynamics of surface runoff. As the patches patch cohesion decreased, the splitting increased, which caused the surface runoff velocity increase, the resistance decrease, and the slope erosion became more severe.}, } @article {pmid33752093, year = {2021}, author = {Pejcic, S and Najjari, MR and Bisleri, G and Rival, DE}, title = {Characterization of the dynamic viscoelastic response of the ascending aorta imposed via pulsatile flow.}, journal = {Journal of the mechanical behavior of biomedical materials}, volume = {118}, number = {}, pages = {104395}, doi = {10.1016/j.jmbbm.2021.104395}, pmid = {33752093}, issn = {1878-0180}, mesh = {Animals ; *Aorta ; Elastic Modulus ; Elasticity ; Pulsatile Flow ; Stress, Mechanical ; Swine ; }, abstract = {This study characterizes the material properties of a viscoelastic, ex vivo porcine ascending aorta under dynamic-loading conditions via pulsatile flow. The deformation of the opaque vessel wall and the pulsatile flow field inside the vessel were recorded using ultrasound imaging. The internal pressure was extracted from the pulsatile flow results and, when coupled with the vessel-wall expansion, was used to calculate the instantaneous elastic modulus from a novel, time-resolved two-dimensional (i.e. axial and circumferential) stress model. The circumferential instantaneous elasticity obtained from the two-dimensional stress model was found to match the uniaxial tensile test for strains below 50%. The agreement in elasticity between the two stress states reveals that the two-dimensional stress model accurately resolves the circumferential stress of the viscoelastic aorta at physiological strains (8%-30%). At higher strains, results from pulsatile flow generated a more compliant response than the uniaxial measurements. Viscoelastic properties (storage modulus and loss factor) were also calculated using the two-dimensional stress model and compared to those obtained from uniaxial tests. While instantaneous elasticity matched between the cylindrical and uniaxial loading, the viscoelastic behaviour significantly diverged between stress states. The storage modulus obtained from the pulsatile flow data was dependent on mean Reynolds number, while the uniaxial storage modulus results exhibited a strong inverse dependency on the frequency. The loss factor for the pulsatile flow data increased alongside the frequency, while the uniaxial data indicated a constant loss factor over the entire frequency range. The results of the current study show that the two-dimensional stress model can accurately extract the material properties of the ex vivo porcine aorta.}, } @article {pmid33748634, year = {2021}, author = {Lu, H and Chen, L and Wang, J and Zhang, X and Li, G and Wang, J and Chen, W and Yan, B}, title = {Using a Modified Turian-Yuan Model to Enhance Heterogeneous Resistance in Municipal Sludge Transportation Pipeline.}, journal = {ACS omega}, volume = {6}, number = {10}, pages = {7199-7211}, pmid = {33748634}, issn = {2470-1343}, abstract = {Based on the Turian-Yuan heterogeneous resistance model, the simulation results of three urban sludge pipelines with a volumetric concentration of 2.38, 3.94, and 5.39% were analyzed. The reasons for the large deviation of the simulation results under high Reynolds number conditions were also analyzed. The results showed that the deviation of the simulation was mainly caused by the difference between the sludge volumetric concentration (C V), the settlement resistance coefficient (C D), and the values of the two parameters in the Turian-Yuan heterogeneous resistance model. Consequently, it was necessary to optimize the index m 1 of C V and the index m 2 of C D. Taking mean square deviation as the objective function, using Matlab programming, the abovementioned two indexes were optimized by the simulated annealing algorithm. The optimized index m 1 of C V was 0.887, and the index m 2 of C D was -0.162. Hence, a modified Turian-Yuan heterogeneous resistance model was obtained. The model verified that the minimum value of the regression coefficient, R 2, of the simulated value reached 0.9701, proving that, the model can be used to simulate the heterogeneous resistance of urban sludge pipeline transportation.}, } @article {pmid33736076, year = {2021}, author = {Tajfirooz, S and Meijer, JG and Kuerten, JGM and Hausmann, M and Fröhlich, J and Zeegers, JCH}, title = {Statistical-learning method for predicting hydrodynamic drag, lift, and pitching torque on spheroidal particles.}, journal = {Physical review. E}, volume = {103}, number = {2-1}, pages = {023304}, doi = {10.1103/PhysRevE.103.023304}, pmid = {33736076}, issn = {2470-0053}, abstract = {A statistical learning approach is presented to predict the dependency of steady hydrodynamic interactions of thin oblate spheroidal particles on particle orientation and Reynolds number. The conventional empirical correlations that approximate such dependencies are replaced by a neural-network-based correlation which can provide accurate predictions for high-dimensional input spaces occurring in flows with nonspherical particles. By performing resolved simulations of steady uniform flow at 1≤Re≤120 around a 1:10 spheroidal body, a database consisting of Reynolds number- and orientation-dependent drag, lift, and pitching torque acting on the particle is collected. A multilayer perceptron is trained and validated with the generated database. The performance of the neural network is tested in a point-particle simulation of the buoyancy-driven motion of a 1:10 disk. Our statistical approach outperforms existing empirical correlations in terms of accuracy. The agreement between the numerical results and the experimental observations prove the potential of the method.}, } @article {pmid33731341, year = {2021}, author = {Corbetta, A and Menkovski, V and Benzi, R and Toschi, F}, title = {Deep learning velocity signals allow quantifying turbulence intensity.}, journal = {Science advances}, volume = {7}, number = {12}, pages = {}, pmid = {33731341}, issn = {2375-2548}, abstract = {Turbulence, the ubiquitous and chaotic state of fluid motions, is characterized by strong and statistically nontrivial fluctuations of the velocity field, and it can be quantitatively described only in terms of statistical averages. Strong nonstationarities impede statistical convergence, precluding quantifying turbulence, for example, in terms of turbulence intensity or Reynolds number. Here, we show that by using deep neural networks, we can accurately estimate the Reynolds number within 15% accuracy, from a statistical sample as small as two large-scale eddy turnover times. In contrast, physics-based statistical estimators are limited by the convergence rate of the central limit theorem and provide, for the same statistical sample, at least a hundredfold larger error. Our findings open up previously unexplored perspectives and the possibility to quantitatively define and, therefore, study highly nonstationary turbulent flows as ordinarily found in nature and in industrial processes.}, } @article {pmid33730564, year = {2021}, author = {Wiputra, H and Lim, M and Yap, CH}, title = {A transition point for the blood flow wall shear stress environment in the human fetal left ventricle during early gestation.}, journal = {Journal of biomechanics}, volume = {120}, number = {}, pages = {110353}, doi = {10.1016/j.jbiomech.2021.110353}, pmid = {33730564}, issn = {1873-2380}, mesh = {Computer Simulation ; Female ; *Heart Ventricles/diagnostic imaging ; *Hemodynamics ; Humans ; Hydrodynamics ; Models, Cardiovascular ; Pregnancy ; Stress, Mechanical ; }, abstract = {Development of the fetal heart is a fascinating process that involves a tremendous amount of growth. Here, we performed image-based flow simulations of 3 human fetal left ventricles (LV), and investigated the hypothetical scenario where the sizes of the hearts are scaled down, leading to reduced Reynolds number, to emulate earlier fetal stages. The shape and motion of the LV were retained over the scaling to isolate and understand the effects of length scaling on its fluid dynamics. We observed an interesting cut-off point in Reynolds number (Re), across which the dependency of LV wall shear stress (WSS) on Re changed. This was in line with classical fluid mechanic theory where skin friction coefficient exhibited first a decreasing trend and then a plateauing trend with increasing Re. Below this cut-off point, viscous effects dominated, stifling the formation of LV diastolic vorticity structures, and WSS was roughly independent of Reynolds number. However, above this cut-off, inertial effects dominated to cause diastolic vortex ring formation and detachment, and to cause WSS to scale linearly with Reynolds number. Results suggested that this transition point is found at approximately 11 weeks of gestation. Since WSS is thought to be a biomechanical stimuli for growth, this may have implications on normal fetal heart growth and malformation diseases like Hypoplastic Left Heart Syndrome.}, } @article {pmid33728053, year = {2021}, author = {Kumar, VRS and Choudhary, SK and Radhakrishnan, PK and Bharath, RS and Chandrasekaran, N and Sankar, V and Sukumaran, A and Oommen, C}, title = {Lopsided Blood-Thinning Drug Increases the Risk of Internal Flow Choking Leading to Shock Wave Generation Causing Asymptomatic Cardiovascular Disease.}, journal = {Global challenges (Hoboken, NJ)}, volume = {5}, number = {3}, pages = {2000076}, pmid = {33728053}, issn = {2056-6646}, abstract = {The discovery of Sanal flow choking in the cardiovascular-system calls for multidisciplinary and global action to develop innovative treatments and to develop new drugs to negate the risk of asymptomatic-cardiovascular-diseases. Herein, it is shown that when blood-pressure-ratio (BPR) reaches the lower-critical-hemorrhage-index (LCHI) internal-flow-choking and shock wave generation can occur in the cardiovascular-system, with sudden expansion/divergence/vasospasm or bifurcation regions, without prejudice to the percutaneous-coronary-intervention (PCI). Analytical findings reveal that the relatively high and the low blood-viscosity are cardiovascular-risk factors. In vitro studies have shown that nitrogen, oxygen, and carbon dioxide gases are dominant in fresh blood samples of humans/guinea pigs at a temperature range of 98.6-104 F. An in silico study demonstrated the Sanal flow choking phenomenon leading to shock-wave generation and pressure-overshoot in the cardiovascular-system. It has been established that disproportionate blood-thinning treatment increases the risk of the internal-flow-choking due to the enhanced boundary-layer-blockage-factor, resulting from an increase in flow-turbulence level in the cardiovascular-system, caused by an increase in Reynolds number as a consequence of low blood-viscosity. The cardiovascular-risk can be diminished by concurrently lessening the viscosity of biofluid/blood and flow-turbulence by raising the thermal-tolerance-level in terms of blood-heat-capacity-ratio (BHCR) and/or by decreasing the systolic-to-diastolic blood-pressure-ratio.}, } @article {pmid33723624, year = {2021}, author = {Challita, EJ and Alexander, SLM and Han, SI and Blackledge, TA and Coddington, JA and Jung, S and Bhamla, MS}, title = {Slingshot spiders build tensed, underdamped webs for ultrafast launches and speedy halts.}, journal = {Journal of comparative physiology. A, Neuroethology, sensory, neural, and behavioral physiology}, volume = {207}, number = {2}, pages = {205-217}, pmid = {33723624}, issn = {1432-1351}, mesh = {Animals ; Biomechanical Phenomena/*physiology ; *Models, Theoretical ; Predatory Behavior/physiology ; Silk/*physiology ; Spiders/*physiology ; Time Factors ; Video Recording/methods ; Walking Speed/*physiology ; }, abstract = {We develop a mathematical model to capture the web dynamics of slingshot spiders (Araneae: Theridiosomatidae), which utilize a tension line to deform their orb webs into conical springs to hunt flying insects. Slingshot spiders are characterized by their ultrafast launch speeds and accelerations (exceeding 1300 [Formula: see text]), however a theoretical approach to characterize the underlying spatiotemporal web dynamics remains missing. To address this knowledge gap, we develop a 2D-coupled damped oscillator model of the web. Our model reveals three key insights into the dynamics of slingshot motion. First, the tension line plays a dual role: enabling the spider to load elastic energy into the web for a quick launch (in milliseconds) to displacements of 10-15 body lengths, but also enabling the spider to halt quickly, attenuating inertial oscillations. Second, the dominant energy dissipation mechanism is viscous drag by the silk lines - acting as a low Reynolds number parachute. Third, the web exhibits underdamped oscillatory dynamics through a finely-tuned balance between the radial line forces, the tension line force and viscous drag dissipation. Together, our work suggests that the conical geometry and tension-line enables the slingshot web to act as both an elastic spring and a shock absorber, for the multi-functional roles of risky predation and self-preservation.}, } @article {pmid33721123, year = {2021}, author = {Basha, HT and Sivaraj, R}, title = {Exploring the heat transfer and entropy generation of Ag/Fe[Formula: see text]O[Formula: see text]-blood nanofluid flow in a porous tube: a collocation solution.}, journal = {The European physical journal. E, Soft matter}, volume = {44}, number = {3}, pages = {31}, pmid = {33721123}, issn = {1292-895X}, mesh = {*Entropy ; *Hot Temperature ; Hydrodynamics ; Iron/*chemistry ; Nanotechnology/*instrumentation ; Porosity ; Silver/*chemistry ; }, abstract = {Evaluating the entropy generation is essential in thermal systems to avoid the unnecessarily wasted thermal energy during the thermal processes. Nowadays, researchers are greatly fascinated to scrutinize the entropy generation in a human system because it is utilized as a thermodynamic approach to understand the heat transfer characteristics of cancer systems or wounded tissue and their accessibility status. Further, numerous nanoparticles have been employed as an agent to control the heat transfer of blood and wounded tissue. As a result, the present model manifests the entropy generation, flow characteristics and heat transport of Ag/Fe[Formula: see text]O[Formula: see text]-blood flow of a nanofluid in a permeable circular tube with the influence of variable electrical conductivity and linear radiation. Nonlinear transport equations are converted into ordinary differential equations by suitable similarity variables which are solved with weighted residual method. Significant parameters like Reynolds number, dimensionless permeability parameter, extending/contracting parameter, Eckert number and Hartmann number on the radial pressure, axial velocity, radial velocity and temperature are explored through graphs. The obtained results show that temperature distribution of Fe[Formula: see text]O[Formula: see text] nanoparticles is higher than Ag nanoparticle, in case of suction. The dimensionless permeability parameter has an opposite nature on the radial pressure for the suction and injection cases. Growing values of Hartmann number enhance the total entropy generation for the cases of suction and injection.}, } @article {pmid33719755, year = {2021}, author = {Liu, Z and Zhang, H and Lai, H}, title = {Fluid flow effects on the degradation kinetics of bioresorbable polymers.}, journal = {Computer methods in biomechanics and biomedical engineering}, volume = {24}, number = {10}, pages = {1073-1084}, doi = {10.1080/10255842.2020.1867115}, pmid = {33719755}, issn = {1476-8259}, mesh = {*Absorbable Implants ; Biocompatible Materials ; Kinetics ; *Polymers ; Tissue Scaffolds ; }, abstract = {Implants, tissue engineering scaffolds made of biodegradable polymers are widely used in biomedical engineering. The degradation of polymers plays a critical role in the effectiveness of these applications. In this paper, the mechanism of the hydrolytic degradation affected by the flow medium is studied. The results indicate that both high porosity and dynamic conditions may significantly slow down degradation speed. A critical value of the Reynolds number is found to exist. When the Reynolds number is higher than the critical value, the autocatalysis was suppressed. The models reported in this article might serve as a guide to design 3D biodegradable implants.}, } @article {pmid33713991, year = {2021}, author = {Al-Mubarak, HFI and Vallatos, A and Holmes, WM}, title = {Impact of turbulence-induced asymmetric propagators on the accuracy of phase-contrast velocimetry.}, journal = {Journal of magnetic resonance (San Diego, Calif. : 1997)}, volume = {325}, number = {}, pages = {106929}, doi = {10.1016/j.jmr.2021.106929}, pmid = {33713991}, issn = {1096-0856}, abstract = {Phase-contrast magnetic resonance velocimetry (PC-MRI) has been widely used to investigate flow properties in numerous systems. In a horizontal cylindrical pipe (3 mm diameter), we investigated the accuracy of PC-MRI as the flow transitioned from laminar to turbulent flow (Reynolds number 352-2708). We focus primarily on velocimetry errors introduced by skewed intra-voxel displacement distributions, a consequence of PC-MRI theory assuming symmetric distributions. We demonstrated how rapid fluctuations in the velocity field, can produce broad asymmetric intravoxel displacement distributions near the wall. Depending on the shape of the distribution, this resulted in PC-MRI measurements under-estimating (positive skewness) or over-estimating (negative skewness) the true mean intravoxel velocity, which could have particular importance to clinical wall shear stress measurements. The magnitude of these velocity errors was shown to increase with the variance and decrease with the kurtosis of the intravoxel displacement distribution. These experimental results confirm our previous theoretical analysis, which gives a relationship for PC-MRI velocimetry errors, as a function of the higher moments of the intravoxel displacement distribution (skewness, variance, and kurtosis) and the experimental parameters q and Δ. This suggests that PC-MRI errors in such unsteady/turbulent flow conditions can potentially be reduced by employing lower q values or shorter observation times Δ.}, } @article {pmid33712884, year = {2021}, author = {Cho, M}, title = {Aerodynamics and the role of the earth's electric field in the spiders' ballooning flight.}, journal = {Journal of comparative physiology. A, Neuroethology, sensory, neural, and behavioral physiology}, volume = {207}, number = {2}, pages = {219-236}, pmid = {33712884}, issn = {1432-1351}, mesh = {Animals ; *Earth, Planet ; Electrophysiological Phenomena/*physiology ; Flight, Animal/*physiology ; Silk/*physiology ; Spiders/*physiology ; Static Electricity ; }, abstract = {Some spiders aerially disperse relying on their fine fibres. This behaviour has been known as 'ballooning'. Observations on the ballooning behaviour of spiders have a long history and have more recently received special attention, yet its underlying physics is still poorly understood. It was traditionally believed that spiders rely on the airflows by atmospheric thermal convection to do ballooning. However, a recent experiment showed that exposure to an electric field alone can induce spiders' pre-ballooning behaviours (tiptoe and dropping/dangling) and even pulls them upwards in the air. The controversy between explanations of ballooning by aerodynamic flow or the earth's electric field has long existed. The major obstacle in studying the physics of ballooning is the fact that airflow and electric field are both invisible and our naked eyes can hardly recognise the ballooning silk fibres of spiders. This review explores the theory and evidence for the physical mechanisms of spiders' ballooning connects them to the behavioural physiology of spiders for ballooning. Knowledge gaps that need to be addressed in future studies are identified.}, } @article {pmid33683671, year = {2021}, author = {Riley, JM and Price, NS and Saaid, HM and Good, BC and Aycock, KI and Craven, BA and Manning, KB}, title = {In Vitro Clot Trapping Efficiency of the FDA Generic Inferior Vena Cava Filter in an Anatomical Model: An Experimental Fluid-Structure Interaction Benchmark.}, journal = {Cardiovascular engineering and technology}, volume = {12}, number = {3}, pages = {339-352}, doi = {10.1007/s13239-021-00524-z}, pmid = {33683671}, issn = {1869-4098}, mesh = {Animals ; Benchmarking ; Cattle ; Models, Cardiovascular ; Rheology ; *Thrombosis ; *Vena Cava Filters ; }, abstract = {PURPOSE: Robust experimental data for performing validation of fluid-structure interaction (FSI) simulations of the transport of deformable solid bodies in internal flow are currently lacking. This in vitro experimental study characterizes the clot trapping efficiency of a new generic conical-type inferior vena cava (IVC) filter in a rigid anatomical model of the IVC with carefully characterized test conditions, fluid rheological properties, and clot mechanical properties.

METHODS: Various sizes of spherical and cylindrical clots made of synthetic materials (nylon and polyacrylamide gel) and bovine blood are serially injected into the anatomical IVC model under worst-case exercise flow conditions. Clot trapping efficiencies and their uncertainties are then quantified for each combination of clot shape, size, and material.

RESULTS: Experiments reveal the clot trapping efficiency increases with increasing clot diameter and length, with trapping efficiencies ranging from as low as approximately 42% for small 3.2 mm diameter spherical clots up to 100% for larger clot sizes. Because of the asymmetry of the anatomical IVC model, the data also reveal the iliac vein of clot origin influences the clot trapping efficiency, with the trapping efficiency for clots injected into the left iliac vein up to a factor of 7.5 times greater than that for clots injected into the right iliac (trapping efficiencies of approximately 10% versus 75%, respectively).

CONCLUSION: Overall, this data set provides a benchmark for validating simulations predicting IVC filter clot trapping efficiency and, more generally, low-Reynolds number FSI modeling.}, } @article {pmid33673667, year = {2021}, author = {Mariotti, A and Antognoli, M and Galletti, C and Mauri, R and Salvetti, MV and Brunazzi, E}, title = {A Study on the Effect of Flow Unsteadiness on the Yield of a Chemical Reaction in a T Micro-Reactor.}, journal = {Micromachines}, volume = {12}, number = {3}, pages = {}, pmid = {33673667}, issn = {2072-666X}, abstract = {Despite the very simple geometry and the laminar flow, T-shaped microreactors have been found to be characterized by different and complex steady and unsteady flow regimes, depending on the Reynolds number. In particular, flow unsteadiness modifies strongly the mixing process; however, little is known on how this change may affect the yield of a chemical reaction. In the present work, experiments and 3-dimensional numerical simulations are carried out jointly to analyze mixing and reaction in a T-shaped microreactor with the ultimate goal to investigate how flow unsteadiness affects the reaction yield. The onset of the unsteady asymmetric regime enhances the reaction yield by more than 30%; however, a strong decrease of the yield back to values typical of the vortex regime is observed when the flow undergoes a transition to the unsteady symmetric regime.}, } @article {pmid33672972, year = {2021}, author = {Gao, Y and Magaud, P and Baldas, L and Wang, Y}, title = {Inertial Migration of Neutrally Buoyant Spherical Particles in Square Channels at Moderate and High Reynolds Numbers.}, journal = {Micromachines}, volume = {12}, number = {2}, pages = {}, pmid = {33672972}, issn = {2072-666X}, support = {BK20200336//Natural Science Foundation of Jiangsu Province/ ; }, abstract = {The inertial migration of particles in microchannel flows has been deeply investigated in the last two decades. In spite of numerous reports on the inertial focusing patterns in a square channel, the particle inertial focusing and longitudinal ordering processes remain unclear at high Reynolds numbers (>200) in square microchannels smaller than 100 µm in width. Thus, in this work, in situ visualization of particles flowing in square micro-channels at Reynolds numbers Re ranging from 5 to 280 has been conducted and their migration behaviors have been analyzed. The obtained results confirm that new equilibrium positions appear above a critical Re depending on the particle to channel size ratio and the particle volume fraction. It is also shown that, for a given channel length, an optimal Reynolds number can be identified, for which the ratio of particles located on equilibrium positions is maximal. Moreover, the longitudinal ordering process, i.e., the formation of trains of particles on equilibrium positions and the characterization of their length, has also been analyzed for the different flow conditions investigated in this study.}, } @article {pmid33670962, year = {2021}, author = {Xie, GF and Zhao, L and Dong, YY and Li, YG and Zhang, SL and Yang, C}, title = {Hydraulic and Thermal Performance of Microchannel Heat Sink Inserted with Pin Fins.}, journal = {Micromachines}, volume = {12}, number = {3}, pages = {}, pmid = {33670962}, issn = {2072-666X}, abstract = {With the development of micromachining technologies, a wider use of microchannel heat sink (MCHS) is achieved in many fields, especially for cooling electronic chips. A microchannel with a width of 500 μm and a height of 500 μm is investigated through the numerical simulation method. Pin fins are arranged at an inclined angle of 0°, 30°, 45°, and 60°, when arrangement method includes in-lined pattern and staggered pattern. The effects of inclined angle and arrangement method on flow field and temperature field of MCHSs are studied when Reynolds number ranges from 10 to 300. In addition to this, quantitative analyses of hydraulic and thermal performance are also discussed in this work. With the increase of inclined angle, the variation of friction factor and Nusselt number do not follow certain rules. The best thermal performance is achieved in MCHS with in-lined fines at an inclined angle of 30° accompanied with the largest friction factor. Arrangement method of pin fins plays a less significant role compared with inclined angle from a general view, particularly in the Reynolds number range of 100~300.}, } @article {pmid33670569, year = {2021}, author = {Malviya, R and Jha, S and Fuloria, NK and Subramaniyan, V and Chakravarthi, S and Sathasivam, K and Kumari, U and Meenakshi, DU and Porwal, O and Sharma, A and Kumar, DH and Fuloria, S}, title = {Determination of Temperature-Dependent Coefficients of Viscosity and Surface Tension of Tamarind Seeds (Tamarindus indica L.) Polymer.}, journal = {Polymers}, volume = {13}, number = {4}, pages = {}, pmid = {33670569}, issn = {2073-4360}, abstract = {The rheological properties of tamarind seed polymer are characterized for its possible commercialization in the food and pharmaceutical industry. Seed polymer was extracted using water as a solvent and ethyl alcohol as a precipitating agent. The temperature's effect on the rheological behavior of the polymeric solution was studied. In addition to this, the temperature coefficient, viscosity, surface tension, activation energy, Gibbs free energy, Reynolds number, and entropy of fusion were calculated by using the Arrhenius, Gibbs-Helmholtz, Frenkel-Eyring, and Eotvos equations, respectively. The activation energy of the gum was found to be 20.46 ± 1.06 kJ/mol. Changes in entropy and enthalpy were found to be 23.66 ± 0.97 and -0.10 ± 0.01 kJ/mol, respectively. The calculated amount of entropy of fusion was found to be 0.88 kJ/mol. A considerable decrease in apparent viscosity and surface tension was produced when the temperature was raised. The present study concludes that the tamarind seed polymer solution is less sensitive to temperature change in comparison to Albzia lebbac gum, Ficus glumosa gum and A. marcocarpa gum. This study also concludes that the attainment of the transition state of viscous flow for tamarind seed gum is accompanied by bond breaking. The excellent physicochemical properties of tamarind seed polymers make them promising excipients for future drug formulation and make their application in the food and cosmetics industry possible.}, } @article {pmid33669613, year = {2021}, author = {Hossain, S and Tayeb, NT and Islam, F and Kaseem, M and Bui, PDH and Bhuiya, MMK and Aslam, M and Kim, KY}, title = {Enhancement of Mixing Performance of Two-Layer Crossing Micromixer through Surrogate-Based Optimization.}, journal = {Micromachines}, volume = {12}, number = {2}, pages = {}, pmid = {33669613}, issn = {2072-666X}, abstract = {Optimum configuration of a micromixer with two-layer crossing microstructure was performed using mixing analysis, surrogate modeling, along with an optimization algorithm. Mixing performance was used to determine the optimum designs at Reynolds number 40. A surrogate modeling method based on a radial basis neural network (RBNN) was used to approximate the value of the objective function. The optimization study was carried out with three design variables; viz., the ratio of the main channel thickness to the pitch length (H/PI), the ratio of the thickness of the diagonal channel to the pitch length (W/PI), and the ratio of the depth of the channel to the pitch length (d/PI). Through a primary parametric study, the design space was constrained. The design points surrounded by the design constraints were chosen using a well-known technique called Latin hypercube sampling (LHS). The optimal design confirmed a 32.0% enhancement of the mixing index as compared to the reference design.}, } @article {pmid33667105, year = {2021}, author = {Brik, M and Harmand, S and Zaaroura, I and Saboni, A}, title = {Experimental and Numerical Study for the Coalescence Dynamics of Vertically Aligned Water Drops in Oil.}, journal = {Langmuir : the ACS journal of surfaces and colloids}, volume = {37}, number = {10}, pages = {3139-3147}, doi = {10.1021/acs.langmuir.0c03624}, pmid = {33667105}, issn = {1520-5827}, abstract = {In this paper, we propose an experimental and numerical investigation for the impact of the surface tension and the continuous phase viscosity on the dynamics of the liquid bridge during the coalescence process in liquid-liquid systems. A specific configuration of a sessile drop in direct contact with another drop placed over it has been studied. Calculating the redefined Reynolds number Re, it is found that for all studied cases, the coalescence process is dominated by the inertial force. The first step of the work was the validation of the numerical model that has been performed in an axisymmetric coordinate system. This has been done by the comparison between numerical and experimental results obtained in the framework of experimental series realized in parallel for two different liquid-liquid (LL) systems: water drops in silicone oil (SilOil M40.165) and water drops in sunflower oil. A good agreement was found between different results for numerous parameters used for comparisons. It is found that for the first stages of the coalescence (at the start of the drops merging), for a given drop's viscosity, the dynamics of the dimensionless liquid bridge is conducted by the viscosity of the continuous phase where it is illustrated that the more the surrounded viscosity is large, the lower the rate of the liquid bridge growth, the lower the earlier radial velocity of the bridge, and the higher the external capillary pressure generated around the bridge. Moreover, it is depicted that the impact of the surface tension starts appearing after the complete development of the liquid bridge where it is observed that for the same surrounding phase viscosity, the propagation of the capillary wave is faster for a LL system with higher surface tensions than those of lower surface tensions.}, } @article {pmid33666462, year = {2021}, author = {Buaria, D and Clay, MP and Sreenivasan, KR and Yeung, PK}, title = {Turbulence is an Ineffective Mixer when Schmidt Numbers Are Large.}, journal = {Physical review letters}, volume = {126}, number = {7}, pages = {074501}, doi = {10.1103/PhysRevLett.126.074501}, pmid = {33666462}, issn = {1079-7114}, abstract = {We solve the advection-diffusion equation for a stochastically stationary passive scalar θ, in conjunction with forced 3D Navier-Stokes equations, using direct numerical simulations in periodic domains of various sizes, the largest being 8192^{3} . The Taylor-scale Reynolds number varies in the range 140-650 and the Schmidt number Sc≡ν/D in the range 1-512, where ν is the kinematic viscosity of the fluid and D is the molecular diffusivity of θ. Our results show that turbulence becomes an ineffective mixer when Sc is large. First, the mean scalar dissipation rate ⟨χ⟩=2D⟨|∇θ|^{2} ⟩, when suitably nondimensionalized, decreases as 1/logSc. Second, 1D cuts through the scalar field indicate increasing density of sharp fronts on larger scales, oscillating with large excursions leading to reduced mixing, and additionally suggesting weakening of scalar variance flux across the scales. The scaling exponents of the scalar structure functions in the inertial-convective range appear to saturate with respect to the moment order and the saturation exponent approaches unity as Sc increases, qualitatively consistent with 1D cuts of the scalar.}, } @article {pmid33665269, year = {2021}, author = {Sleiti, AK}, title = {Dataset for measured viscosity of Polyalpha-Olefin- boron nitride nanofluids.}, journal = {Data in brief}, volume = {35}, number = {}, pages = {106881}, doi = {10.1016/j.dib.2021.106881}, pmid = {33665269}, issn = {2352-3409}, abstract = {Datasets of measured viscosity of Polyalpha-Olefin- boron nitride (PAO/hBN) nanofluids are reported. An AR-G2 rheometer (from TA Instruments) experimental setup is used for measuring the rheological property of PAO/hBN nanofluids, which is a combined motor and transducer (CMT) instrument. The test fluid sample size is approximately 1.5 ml and the tests were conducted over a temperature range of the tested fluids from - 20 °C to 70 °C by a water circulator chamber. The dataset includes measured viscosities as a function of the BN volumetric concentration (ϕ) of 0, 0.6 and 1%. Two sets of viscosity measurements are conducted insuring the thermal equilibrium conditions are reached for all experiments. In set (1), the viscosity is measured at intervals of 10 °C by fixing the temperature at each interval (at -20, -10, 0, 10, 20, 30, 40, 50, 60 and 70 °C), while the shear stress and shear rate are varied. In set (2), the temperature is varied from -20 °C to 70 °C at intervals of 0.5 °C, while the shear stress is fixed and the shear rate is varied accordingly. Set (1) is designed to verify whether the fluids are Newtonian or not and set (2) is designed to derive correlations for the viscosity as a function of temperature. Several characteristics data are recorded including rotational speed of the spindle (RPM), torque, viscosity (Pa- s), shear stress (Pa), shear strain rate (1/s) and temperature (°C). The reuse potential of the dataset includes calculating Reynolds number for further flow studies; heat transfer performance studies of nanofluids; lubrication and lubricants' development studies and characteristics of Newtonian and non-Newtonian fluids. The dataset reported here were used (but not published) in the article published by the author in [1] (https://doi.org/10.1016/j.csite.2020.100776).}, } @article {pmid33652896, year = {2021}, author = {Charlton, AJ and Blandin, G and Leslie, G and Le-Clech, P}, title = {Impact of Forward Osmosis Operating Pressure on Deformation, Efficiency and Concentration Polarisation with Novel Links to CFD.}, journal = {Membranes}, volume = {11}, number = {3}, pages = {}, pmid = {33652896}, issn = {2077-0375}, abstract = {Forward osmosis (FO) modules currently suffer from performance efficiency limitations due to concentration polarisation (CP), as well as pressure drops during operation. There are incentives to further reduce CP effects, as well as optimise spacer design for pressure drop improvements and mechanical support. In this study, the effects of applying transmembrane pressure (TMP) on FO membrane deformation and the subsequent impact on module performance was investigated by comparing experimental data to 3D computational fluid dynamics (CFD) simulations for three commercial FO modules. At a TMP of 1.5 bar the occlusion of the draw-channel induced by longitudinal pressure hydraulic drop was comparable for the Toray (16%) and HTI modules (12%); however, the hydraulic perimeter of the Profiera module was reduced by 46%. CFD simulation of the occluded channels indicated that a change in hydraulic perimeter due to a 62% increase in shear strain resulted in a 31% increase in the Reynolds number. This reduction in channel dimensions enhanced osmotic efficiency by reducing CP via improved draw-channel hydrodynamics, which significantly disrupted the external concentration polarization (ECP) layer. Furthermore, simulations indicated that the Reynolds number experienced only modest increases with applied TMP and that shear strain at the membrane surface was found to be the most important factor when predicting flux performance enhancement, which varied between the different modules. This work suggests that a numerical approach to assess the effects of draw-spacers on pressure drop and CP can optimize and reduce investment in the design and validation of FO module designs.}, } @article {pmid33639789, year = {2021}, author = {Ramadan, IA and Bailliet, H and Valière, JC}, title = {Experimental investigation of oscillating flow characteristics at the exit of a stacked mesh grid regenerator.}, journal = {The Journal of the Acoustical Society of America}, volume = {149}, number = {2}, pages = {807}, doi = {10.1121/10.0003375}, pmid = {33639789}, issn = {1520-8524}, abstract = {The aim of this study is to investigate the oscillating flow velocity field at the exit of different stacked mesh grid regenerators using Particle Image Velocimetry measurements. Twelve different experimental cases are discussed, yielding oscillating flow fields at the exit of four kinds of regenerators for different acoustic levels. The regenerators are classified according to the mesh wire size to viscous penetration depth ratio and according to the method of stacking the mesh grids. Based on the analysis of the vorticity fields at the exit of the regenerator, three groups of flow patterns are identified. This classification is correctly verified by using the Reynolds number (based on the acoustic amplitude and wire diameter) and the Strouhal number (based on the acoustic displacement amplitude and wire diameter). The characteristics of the fluctuating velocity components are investigated for these various flow patterns. The critical Reynolds number, past which the flow is highly dissipative, is determined. The dissipation timescale is investigated and the quasi-steady approximation is found to be valid for the analysis of the oscillating flow at the exit of the regenerator mesh.}, } @article {pmid33635696, year = {2021}, author = {Bakhuis, D and Ezeta, R and Bullee, PA and Marin, A and Lohse, D and Sun, C and Huisman, SG}, title = {Catastrophic Phase Inversion in High-Reynolds-Number Turbulent Taylor-Couette Flow.}, journal = {Physical review letters}, volume = {126}, number = {6}, pages = {064501}, doi = {10.1103/PhysRevLett.126.064501}, pmid = {33635696}, issn = {1079-7114}, abstract = {Emulsions are omnipresent in the food industry, health care, and chemical synthesis. In this Letter the dynamics of metastable oil-water emulsions in highly turbulent (10^{11} ≤Ta≤3×10^{13} ) Taylor-Couette flow, far from equilibrium, is investigated. By varying the oil-in-water void fraction, catastrophic phase inversion between oil-in-water and water-in-oil emulsions can be triggered, changing the morphology, including droplet sizes, and rheological properties of the mixture, dramatically. The manifestation of these different states is exemplified by combining global torque measurements and local in situ laser induced fluorescence microscopy imaging. Despite the turbulent state of the flow and the dynamic equilibrium of the oil-water mixture, the global torque response of the system is found to be as if the fluid were Newtonian, and the effective viscosity of the mixture was found to be several times bigger or smaller than either of its constituents.}, } @article {pmid33635462, year = {2021}, author = {Jain, PK and Lanjewar, A and Jain, R and Rana, KB}, title = {Performance analysis of multi-gap V-roughness with staggered elements of solar air heater based on artificial neural network and experimental investigations.}, journal = {Environmental science and pollution research international}, volume = {}, number = {}, pages = {}, pmid = {33635462}, issn = {1614-7499}, abstract = {Among all renewable energy sources, solar power is one of the major sources which contributes for pollution control and protection of environment. For a number of decades, technologies for utilizing the solar power have been the area of research and development. In the current research, thermal performance parameters of multi-gap V-roughness with staggered elements of a solar air heater (SAH) are experimentally investigated. The artificial neural network (ANN) is also utilized for predicting the thermal performance parameters of SAH. Experiments were executed in a rectangular channel with one roughened side at the top exposed to a uniform heat flux. A significant rise in thermal efficiency performance was reported under a predefined range of Reynolds number (Re) from 3000 to 14000 with an optimized value of relative roughness pitch ratio (P/e) and relative staggered rib length (w/g) as 12 and 1, respectively. The maximum thermal efficiency was attained in the range from 42.15 to 87.02% under considered Reynolds numbers for optimum value of P/e as 12 and w/g as 1. A multilayered perceptron (MLP) feed-forward ANN trained by the Broyden-Fletcher-Goldfarb-Shanno (BFGS) algorithm was utilized to predict the thermal efficiency (ηth), friction (f), and Nusselt number (Nu). The thermal performance parameters such as P/e, w/g, Re, and temperature at the inlet, outlet, and plate were the critical input parameters/signals used in the ANN method. The optimum ANN arrangement/structure to predict the Nu, f, and ηth demonstrate higher accurateness in assessing the performance characteristics of SAH by attaining the root mean squared error (RMSE) in prediction and the Pearson coefficient of association (R2) of 1.591 and 0.994; 0.0012 and 0.851; and 0.025 and 0.981, respectively. The prediction profile plots of the ANN demonstrate the influence of various input parameters on the thermal performance parameters.}, } @article {pmid33633249, year = {2021}, author = {Altmeyer, S}, title = {On the ridge of instability in ferrofluidic Couette flow via alternating magnetic field.}, journal = {Scientific reports}, volume = {11}, number = {1}, pages = {4705}, pmid = {33633249}, issn = {2045-2322}, abstract = {There is a huge number of natural and industrial flows, which are subjected to time-dependent boundary conditions. The flow of a magnetic fluid under the influence of temporal modulations is such an example. Here, we perform numerical simulations of ferrofluidic Couette flow subject to time-periodic modulation (with frequency [Formula: see text]) in a spatially homogeneous magnetic field and report how such a modulation can lead to a significant Reynolds number Re enhancement. Consider a modified Niklas approximation we explain the relation between modulation amplitude, driving frequency and stabilization effect. From this, we describe the system response around the primary instability to be sensitive/critical by an alternating field. We detected that such an alternating field provides an easy and in particular accurate controllable key parameter to trigger the system to change from subcritical to supercritical and vice versa. Our findings provide a framework to study other types of magnetic flows driven by time-dependent forcing.}, } @article {pmid33625506, year = {2021}, author = {Sera, T and Kamiya, N and Fukushima, T and Tanaka, G}, title = {Visualizing the Flow Patterns in an Expanding and Contracting Pulmonary Alveolated Duct Based on Microcomputed Tomography Images.}, journal = {Journal of biomechanical engineering}, volume = {143}, number = {7}, pages = {}, doi = {10.1115/1.4050285}, pmid = {33625506}, issn = {1528-8951}, mesh = {*Lung ; }, abstract = {We visualized the flow patterns in an alveolated duct model with breathing-like expanding and contracting wall motions using particle image velocimetry, and then, we investigated the effect of acinar deformation on the flow patterns. We reconstructed a compliant, scaled-up model of an alveolated duct from synchrotron microcomputed tomography images of a mammalian lung. The alveolated duct did not include any bifurcation, and its entire surface was covered with alveoli. We embedded the alveolated duct in a sealed container that was filled with fluid. We oscillated the fluid in the duct and container simultaneously and independently to control the flow and duct volume. We examined the flow patterns in alveoli, with the Reynolds number (Re) at 0.03 or 0.22 and the acinar volume change at 0%, 20%, or 80%. At the same Re, the heterogeneous deformation induced different inspiration and expiration flow patterns, and the recirculating regions in alveoli changed during respiratory cycle. During a larger acinar deformation at Re = 0.03, the flow patterns tended to change from recirculating flow to radial flow during inspiration and vice versa during expiration. Additionally, the alveolar geometric characteristics, particularly the angle between the alveolar duct and mouth, affected these differences in flow patterns. At Re = 0.22, recirculating flow patterns tended to form during inspiration and expiration, regardless of the magnitude of the acinar deformation. Our in vitro experiments suggest that the alveolated flows with nonself-similar and heterogeneous wall motions may promote particle mixing and deposition.}, } @article {pmid33622143, year = {2021}, author = {Pepper, RE and Riley, EE and Baron, M and Hurot, T and Nielsen, LT and Koehl, MAR and Kiørboe, T and Andersen, A}, title = {The effect of external flow on the feeding currents of sessile microorganisms.}, journal = {Journal of the Royal Society, Interface}, volume = {18}, number = {175}, pages = {20200953}, pmid = {33622143}, issn = {1742-5662}, mesh = {*Ecosystem ; *Feeding Behavior ; Suspensions ; }, abstract = {Microscopic sessile suspension feeders live attached to surfaces and, by consuming bacteria-sized prey and by being consumed, they form an important part of aquatic ecosystems. Their environmental impact is mediated by their feeding rate, which depends on a self-generated feeding current. The feeding rate has been hypothesized to be limited by recirculating eddies that cause the organisms to feed from water that is depleted of food particles. However, those results considered organisms in still water, while ambient flow is often present in their natural habitats. We show, using a point-force model, that even very slow ambient flow, with speed several orders of magnitude less than that of the self-generated feeding current, is sufficient to disrupt the eddies around perpendicular suspension feeders, providing a constant supply of food-rich water. However, the feeding rate decreases in external flow at a range of non-perpendicular orientations due to the formation of recirculation structures not seen in still water. We quantify the feeding flow and observe such recirculation experimentally for the suspension feeder Vorticella convallaria in external flows typical of streams and rivers.}, } @article {pmid33622097, year = {2021}, author = {Ge-JiLe, H and Javid, K and Khan, SU and Raza, M and Khan, MI and Qayyum, S}, title = {Double diffusive convection and Hall effect in creeping flow of viscous nanofluid through a convergent microchannel: a biotechnological applications.}, journal = {Computer methods in biomechanics and biomedical engineering}, volume = {24}, number = {12}, pages = {1326-1343}, doi = {10.1080/10255842.2021.1888373}, pmid = {33622097}, issn = {1476-8259}, mesh = {*Convection ; Diffusion ; *Peristalsis ; Rheology ; Viscosity ; }, abstract = {Current analysis presents the mathematical modeling for peristaltic transport of nanofluid with applications of double-diffusive convection and Hall features. The flow has been induced by a convergent channel due to peristaltic propulsion. These rheological equations are transformed from fixed to wave frames by using a linear mathematical relation between these two frames. The dimensionless variables are used to transform these rheological equations into nondimensional forms. The flow analysis is carried out under two distinct scientific biological assumptions, one is known as long wavelength and the second one is low Reynolds number. The analytical solutions of these rheological equations are obtained with the help of a rigorous analytical method known as integration in the term of stream function. The physical effects of magnetic and Hall devices, respectively, on the flow features are also considered in the present analysis. The physical influences of dominant hydro-mechanical parameters on the axial velocity, pressure gradient, trapping, volumetric fraction of nanofluid, heat and mass transfer phenomena are studied. The complex scenario of biomimetic propulsions are considered in boundary walls to boost the proficiency of peristaltic micropumps.}, } @article {pmid33601572, year = {2021}, author = {Bao, G and Jian, Y}, title = {Odd-viscosity-induced instability of a falling thin film with an external electric field.}, journal = {Physical review. E}, volume = {103}, number = {1-1}, pages = {013104}, doi = {10.1103/PhysRevE.103.013104}, pmid = {33601572}, issn = {2470-0053}, abstract = {The influence of odd viscosity of Newtonian fluid on the instability of thin film flowing along an inclined plane under a normal electric field is studied. By odd viscosity, we mean apart from the well-known coefficient of shear viscosity, a classical liquid with broken time-reversal symmetry is endowed with a second viscosity coefficient in biological, colloidal, and granular systems. Under the long wave approximation, a nonlinear evolution equation of the free surface is derived by the method of systematic asymptotic expansion. The effects of the odd viscosity and external electric field are considered in this evolution equation and an analytical expression of critical Reynolds number is obtained. It is interesting to find that, by linear stability analysis, the critical Reynolds number increases with odd viscosity and decreases with external strength of electric field. In other words, odd viscosity has a stable effect and electric field has a destabilized effect on flowing of thin film. In addition, through nonlinear analysis, we obtain a Ginsburg-Landau equation and find that the film has not only the supercritical stability zone and the subcritical instability zone but also the unconditional stability zone and the explosive zone. The variations of each zone with related parameters, such as the strength of electric field, odd viscosity, and Reynolds number, etc., are investigated. The results are conducive to the further development of related experiments.}, } @article {pmid33601565, year = {2021}, author = {Pereira, FS and Grinstein, FF and Israel, DM and Rauenzahn, R}, title = {Molecular viscosity and diffusivity effects in transitional and shock-driven mixing flows.}, journal = {Physical review. E}, volume = {103}, number = {1-1}, pages = {013106}, doi = {10.1103/PhysRevE.103.013106}, pmid = {33601565}, issn = {2470-0053}, abstract = {This paper investigates the importance of molecular viscosity and diffusivity for the prediction of transitional and shock-driven mixing flows featuring high and low Reynolds and Mach number regions. Two representative problems are computed with implicit large-eddy simulations using the inviscid Euler equations (EE) and viscous Navier-Stokes equations (NSE): the Taylor-Green vortex at Reynolds number Re=3000 and initial Mach number Ma=0.28, and an air-SF_{6} -air gas curtain subjected to two shock waves at Ma=1.2. The primary focus is on differences between NSE and EE predictions due to viscous effects. The outcome of the paper illustrates the advantages of utilizing NSE. In contrast to the EE, where the effective viscosity decreases upon grid refinement, NSE predictions can be assessed for simulations of flows with transition to turbulence at prescribed constant Re. The NSE can achieve better agreement between solutions and reference data, and the results converge upon grid refinement. On the other hand, the EE predictions do not converge with grid refinement, and can only exhibit similarities with the NSE results at coarse grid resolutions. We also investigate the effect of viscous effects on the dynamics of the coherent and turbulent fields, as well as on the mechanisms contributing to the production and diffusion of vorticity. The results show that nominally inviscid calculations can exhibit significantly varying flow dynamics driven by changing effective resolution-dependent Reynolds number, and highlight the role of viscous processes affecting the vorticity field. These tendencies become more pronounced upon grid refinement. The discussion of the results concludes with the assessment of the computational cost of inviscid and viscous computations.}, } @article {pmid33601495, year = {2021}, author = {Livi, C and Di Staso, G and Clercx, HJH and Toschi, F}, title = {Influence of numerical resolution on the dynamics of finite-size particles with the lattice Boltzmann method.}, journal = {Physical review. E}, volume = {103}, number = {1-1}, pages = {013303}, doi = {10.1103/PhysRevE.103.013303}, pmid = {33601495}, issn = {2470-0053}, abstract = {We investigate and compare the accuracy and efficiency of different numerical approaches to model the dynamics of finite-size particles using the lattice Boltzmann method (LBM). This includes the standard bounce-back (BB) and the equilibrium interpolation (EI) schemes. To accurately compare the different implementations, we first introduce a boundary condition to approximate the flow properties of an unbounded fluid in a finite simulation domain, taking into account the perturbation induced by a moving particle. We show that this boundary treatment is efficient in suppressing detrimental effects on the dynamics of spherical and ellipsoidal particles arising from the finite size of the simulation domain. We then investigate the performances of the BB and EI schemes in modeling the dynamics of a spherical particle settling under Stokes conditions, which can now be reproduced with great accuracy thanks to the treatment of the exterior boundary. We find that the EI scheme outperforms the BB scheme in providing a better accuracy scaling with respect to the resolution of the settling particle, while suppressing finite-size effects due to the particle discretization on the lattice grid. Additionally, in order to further increase the capability of the algorithm in modeling particles of sizes comparable to the lattice spacing, we propose an improvement to the EI scheme, the complete equilibrium interpolation (CEI). This approach allows us to accurately capture the boundaries of the particle also when located between two fluid nodes. We evaluate the CEI performance in solving the dynamics of an under-resolved particle under analogous Stokes conditions and also for the case of a rotating ellipsoid in a shear flow. Finally, we show that EI and CEI are able to recover the correct flow solutions also at small, but finite, Reynolds number. Adopting the CEI scheme it is not only possible to detect particles with zero lattice occupation, but also to increase up to one order of magnitude the accuracy of the dynamics of particles with a size comparable to the lattice spacing with respect to the BB and the EI schemes.}, } @article {pmid33590890, year = {2021}, author = {Pskowski, A and Bagchi, P and Zahn, JD}, title = {Investigation of red blood cell partitioning in an in vitro microvascular bifurcation.}, journal = {Artificial organs}, volume = {45}, number = {9}, pages = {1083-1096}, doi = {10.1111/aor.13941}, pmid = {33590890}, issn = {1525-1594}, support = {CBET 1604308//National Science Foundation/ ; }, mesh = {Blood Flow Velocity ; Equipment Design ; Erythrocytes/*physiology ; *Hematocrit ; Hemorheology/*physiology ; Humans ; In Vitro Techniques ; Microcirculation ; Models, Cardiovascular ; }, abstract = {There is a long history of research examining red blood cell (RBC) partitioning in microvasculature bifurcations. These studies commonly report results describing partitioning that exists as either regular partitioning, which occurs when the RBC flux ratio is greater than the bulk fluid flowrate ratio, or reverse partitioning when the RBC flux ratio is less than or equal to that of the bulk fluid flowrate. This paper presents a study of RBC partitioning in a single bifurcating microchannel with dimensions of 6 to 16 μm, investigating the effects of hematocrit, channel width, daughter channel flowrate ratio, and bifurcation angle. The erythrocyte flux ratio, N*, manifests itself as either regular or reverse partitioning, and time-dependent partitioning is much more dynamic, occurring as both regular and reverse partitioning. We report a significant reduction in the well-known sigmoidal variation of the erythrocyte flux ratio (N*) versus the volumetric flowrate ratio (Q*), partitioning behavior with increasing hematocrit in microchannels when the channel dimensions are comparable with cell size. RBCs "lingering" or jamming at the bifurcation were also observed and quantified in vitro. Results from trajectory analyses suggest that the RBC position in the feeder channel strongly affects both partitioning and lingering frequency of RBCs, with both being significantly reduced when RBCs flow on streamlines near the edge of the channel as opposed to the center of the channel. Furthermore, our experiments suggest that even at low Reynolds number, partitioning is affected by the bifurcation angle by increasing cell-cell interactions. The presented results provide further insight into RBC partitioning as well as perfusion throughout the microvasculature.}, } @article {pmid33580288, year = {2021}, author = {Ender, H and Kierfeld, J}, title = {From diffusive mass transfer in Stokes flow to low Reynolds number Marangoni boats.}, journal = {The European physical journal. E, Soft matter}, volume = {44}, number = {1}, pages = {4}, pmid = {33580288}, issn = {1292-895X}, abstract = {We present a theory for the self-propulsion of symmetric, half-spherical Marangoni boats (soap or camphor boats) at low Reynolds numbers. Propulsion is generated by release (diffusive emission or dissolution) of water-soluble surfactant molecules, which modulate the air-water interfacial tension. Propulsion either requires asymmetric release or spontaneous symmetry breaking by coupling to advection for a perfectly symmetrical swimmer. We study the diffusion-advection problem for a sphere in Stokes flow analytically and numerically both for constant concentration and constant flux boundary conditions. We derive novel results for concentration profiles under constant flux boundary conditions and for the Nusselt number (the dimensionless ratio of total emitted flux and diffusive flux). Based on these results, we analyze the Marangoni boat for small Marangoni propulsion (low Peclet number) and show that two swimming regimes exist, a diffusive regime at low velocities and an advection-dominated regime at high swimmer velocities. We describe both the limit of large Marangoni propulsion (high Peclet number) and the effects from evaporation by approximative analytical theories. The swimming velocity is determined by force balance, and we obtain a general expression for the Marangoni forces, which comprises both direct Marangoni forces from the surface tension gradient along the air-water-swimmer contact line and Marangoni flow forces. We unravel whether the Marangoni flow contribution is exerting a forward or backward force during propulsion. Our main result is the relation between Peclet number and swimming velocity. Spontaneous symmetry breaking and, thus, swimming occur for a perfectly symmetrical swimmer above a critical Peclet number, which becomes small for large system sizes. We find a supercritical swimming bifurcation for a symmetric swimmer and an avoided bifurcation in the presence of an asymmetry.}, } @article {pmid33573067, year = {2021}, author = {Hosseini, SA and Safari, H and Thevenin, D}, title = {Lattice Boltzmann Solver for Multiphase Flows: Application to High Weber and Reynolds Numbers.}, journal = {Entropy (Basel, Switzerland)}, volume = {23}, number = {2}, pages = {}, pmid = {33573067}, issn = {1099-4300}, support = {TRR287-422037413//Deutsche Forschungsgemeinschaft/ ; }, abstract = {The lattice Boltzmann method, now widely used for a variety of applications, has also been extended to model multiphase flows through different formulations. While already applied to many different configurations in low Weber and Reynolds number regimes, applications to higher Weber/Reynolds numbers or larger density/viscosity ratios are still the topic of active research. In this study, through a combination of a decoupled phase-field formulation-the conservative Allen-Cahn equation-and a cumulant-based collision operator for a low-Mach pressure-based flow solver, we present an algorithm that can be used for higher Reynolds/Weber numbers. The algorithm was validated through a variety of test cases, starting with the Rayleigh-Taylor instability in both 2D and 3D, followed by the impact of a droplet on a liquid sheet. In all simulations, the solver correctly captured the flow dynamics andmatched reference results very well. As the final test case, the solver was used to model droplet splashing on a thin liquid sheet in 3D with a density ratio of 1000 and kinematic viscosity ratio of 15, matching the water/air system at We = 8000 and Re = 1000. Results showed that the solver correctly captured the fingering instabilities at the crown rim and their subsequent breakup, in agreement with experimental and numerical observations reported in the literature.}, } @article {pmid33571986, year = {2021}, author = {Gungor, A and Hemmati, A}, title = {Implications of changing synchronization in propulsive performance of side-by-side pitching foils.}, journal = {Bioinspiration & biomimetics}, volume = {16}, number = {3}, pages = {}, doi = {10.1088/1748-3190/abe54b}, pmid = {33571986}, issn = {1748-3190}, mesh = {Animals ; Biomechanical Phenomena ; Fishes ; Hydrodynamics ; *Models, Biological ; *Swimming ; }, abstract = {The unsteady hydrodynamics of side-by-side pitching foils are studied numerically at Reynolds number of 4000 with altering phase differences in the middle of an oscillation cycle. This represents a change in synchronization of oscillating foils, inspired by experimental observations on group swimming of red nose tetra fish. The hybrid oscillation cases are based on an initially out-of-phase pitching that switch to in-phase at the 20th cycle of oscillation. Various sequential combinations of out-of-phase and in-phase pitching are also examined in terms of foil propulsive performance. It is observed that out-of-phase pitching foils initially produce zero total side-force. However, they start producing negative total side-force after 13 oscillation cycles. Contrarily for the in-phase oscillation cases, the initially positive total side-force reverted to zero over time. In hybrid oscillation cases, the negative total side-force produced during the initial out-of-phase oscillations abruptly adjusted to zero following a change of synchronization that led to in-phase oscillations, which is inspired from a particular swimming behavior in fish. Based on three hybrid modes, defined on the onset of mid-cycle switch to in-phase oscillations, it was apparent that the benefit of synchronization, or there lack of, greatly depended on the timing of the change in synchronization. Thus, mid-swimming change of synchronization in side-by-side systems inspired by fish schools compensates for their non-zero total side-force production to maintain their lateral position. Such changes do not translate to significant gains in neither thrust generation nor efficiency.}, } @article {pmid33561405, year = {2021}, author = {Longo, SJ and Ray, W and Farley, GM and Harrison, J and Jorge, J and Kaji, T and Palmer, AR and Patek, SN}, title = {Snaps of a tiny amphipod push the boundary of ultrafast, repeatable movement.}, journal = {Current biology : CB}, volume = {31}, number = {3}, pages = {R116-R117}, doi = {10.1016/j.cub.2020.12.025}, pmid = {33561405}, issn = {1879-0445}, mesh = {*Amphipoda ; Animals ; Biomechanical Phenomena ; Humans ; Male ; *Movement ; Water ; }, abstract = {Surprisingly, the fastest motions are not produced by large animals or robots. Rather, small organisms or structures, including cnidarian stinging cells, fungal shooting spores, and mandible strikes of ants, termites, and spiders, hold the world acceleration records.1-5 These diverse systems share common features: they rapidly convert potential energy - stored in deformed material or fluid - into kinetic energy when a latch is released.4-6 However, the fastest of these are not repeatable, because mechanical components are broken or ejected.5,6 Furthermore, some of these systems must overcome the added challenge of moving in water, where high density and viscosity constrain acceleration at small sizes. Here we report the kinematics of repeatable, ultrafast snaps by tiny marine amphipods (Dulichiella cf. appendiculata). Males use their enlarged major claw, which can exceed 30% of body mass, to snap a 1 mm-long dactyl with a diameter equivalent to a human hair (184 μm). The claw snaps closed extremely rapidly, averaging 93 μs, 17 m s-1, and 2.4 x 105 m s-2. These snaps are among the smallest and fastest of any documented repeatable movement, and are sufficiently fast to operate in the inertial hydrodynamic regime (Reynolds number (Re) >10,000). They generate audible pops and rapid water jets, which occasionally yield cavitation, and may be used for defense. These amphipod snaps push the boundaries of acceleration and size for repeatable movements, particularly in water, and exemplify how new biomechanical insights can arise from unassuming animals. VIDEO ABSTRACT.}, } @article {pmid33544100, year = {2021}, author = {Yang, F}, title = {Homogeneous nucleation in a Poiseuille flow.}, journal = {Physical chemistry chemical physics : PCCP}, volume = {23}, number = {6}, pages = {3974-3982}, doi = {10.1039/d0cp06132h}, pmid = {33544100}, issn = {1463-9084}, abstract = {Nucleation in a dynamical environment plays an important role in the synthesis and manufacturing of quantum dots and nanocrystals. In this work, we investigate the effects of fluid flow (low Reynolds number flow) on the homogeneous nucleation in a circular microchannel in the framework of the classical nucleation theory. The contributions of the configuration entropy from the momentum-phase space and the kinetic energy and strain energy of a microcluster are incorporated in the calculation of the change of the Gibbs free energy from a flow state without a microcluster to a flow state with a microcluster. An analytical equation is derived for the determination of the critical nucleus size. Using this analytical equation, an analytical solution of the critical nucleus size for the formation of a critical liquid nucleus is found. For the formation of a critical solid nucleus, the contributions from both the kinetic energy and the strain energy are generally negligible. We perform numerical analysis of the homogeneous nucleation of a sucrose microcluster in a representative volume element of an aqueous solution, which flows through a circular microchannel. The numerical results reveal the decrease of the critical nucleus size and the corresponding work of formation of a critical nucleus with the increase of the distance to axisymmetric axis for the same numbers of solvent atoms and solute atoms/particles.}, } @article {pmid33543985, year = {2021}, author = {Buaria, D and Clay, MP and Sreenivasan, KR and Yeung, PK}, title = {Small-Scale Isotropy and Ramp-Cliff Structures in Scalar Turbulence.}, journal = {Physical review letters}, volume = {126}, number = {3}, pages = {034504}, doi = {10.1103/PhysRevLett.126.034504}, pmid = {33543985}, issn = {1079-7114}, abstract = {Passive scalars advected by three-dimensional Navier-Stokes turbulence exhibit a fundamental anomaly in odd-order moments because of the characteristic ramp-cliff structures, violating small-scale isotropy. We use data from direct numerical simulations with grid resolution of up to 8192^{3} at high Péclet numbers to understand this anomaly as the scalar diffusivity, D, diminishes, or as the Schmidt number, Sc=ν/D, increases; here ν is the kinematic viscosity of the fluid. The microscale Reynolds number varies from 140 to 650 and Sc varies from 1 to 512. A simple model for the ramp-cliff structures is developed and shown to characterize the scalar derivative statistics very well. It accurately captures how the small-scale isotropy is restored in the large-Sc limit, and additionally suggests a possible correction to the Batchelor length scale as the relevant smallest scale in the scalar field.}, } @article {pmid33543965, year = {2021}, author = {Nasouri, B and Vilfan, A and Golestanian, R}, title = {Minimum Dissipation Theorem for Microswimmers.}, journal = {Physical review letters}, volume = {126}, number = {3}, pages = {034503}, doi = {10.1103/PhysRevLett.126.034503}, pmid = {33543965}, issn = {1079-7114}, abstract = {We derive a theorem for the lower bound on the energy dissipation rate by a rigid surface-driven active microswimmer of arbitrary shape in a fluid at a low Reynolds number. We show that, for any swimmer, the minimum dissipation at a given velocity can be expressed in terms of the resistance tensors of two passive bodies of the same shape with a no-slip and perfect-slip boundary. To achieve the absolute minimum dissipation, the optimal swimmer needs a surface velocity profile that corresponds to the flow around the perfect-slip body, and a propulsive force density that corresponds to the no-slip body. Using this theorem, we propose an alternative definition of the energetic efficiency of microswimmers that, unlike the commonly used Lighthill efficiency, can never exceed unity. We validate the theory by calculating the efficiency limits of spheroidal swimmers.}, } @article {pmid33537715, year = {2021}, author = {Yu, P and Durgesh, V and Xing, T and Budwig, R}, title = {Application of Proper Orthogonal Decomposition to Study Coherent Flow Structures in a Saccular Aneurysm.}, journal = {Journal of biomechanical engineering}, volume = {143}, number = {6}, pages = {}, doi = {10.1115/1.4050032}, pmid = {33537715}, issn = {1528-8951}, mesh = {*Intracranial Aneurysm ; }, abstract = {Aneurysms are localized expansions of weakened blood vessels that can be debilitating or fatal upon rupture. Previous studies have shown that flow in an aneurysm exhibits complex flow structures that are correlated with its inflow conditions. Therefore, the objective of this study was to demonstrate the application of proper orthogonal decomposition (POD) to study the impact of different inflow conditions on energetic flow structures and their temporal behavior in an aneurysm. To achieve this objective, experiments were performed on an idealized rigid sidewall aneurysm model. A piston pump system was used for precise inflow control, i.e., peak Reynolds number (Rep) and Womersley number (α) were varied from 50 to 270 and 2 to 5, respectively. The velocity flow field measurements at the midplane location of the idealized aneurysm model were performed using particle image velocimetry (PIV). The results demonstrate the efficacy of POD in decomposing complex data, and POD was able to capture the energetic flow structures unique to each studied inflow condition. Furthermore, the time-varying coefficient results highlighted the interplay between the coefficients and their corresponding POD modes, which in turn helped explain how POD modes impact certain flow features. The low-order reconstruction results were able to capture the flow evolution and provide information on complex flow in an aneurysm. The POD and low-order reconstruction results also indicated that vortex formation, evolution, and convection varied with an increase in α, while vortex strength and formation of secondary structures were correlated with an increase in Rep.}, } @article {pmid33530578, year = {2021}, author = {Selimefendigil, F and Öztop, HF}, title = {Thermal Management and Modeling of Forced Convection and Entropy Generation in a Vented Cavity by Simultaneous Use of a Curved Porous Layer and Magnetic Field.}, journal = {Entropy (Basel, Switzerland)}, volume = {23}, number = {2}, pages = {}, pmid = {33530578}, issn = {1099-4300}, abstract = {The effects of using a partly curved porous layer on the thermal management and entropy generation features are studied in a ventilated cavity filled with hybrid nanofluid under the effects of inclined magnetic field by using finite volume method. This study is performed for the range of pertinent parameters of Reynolds number (100≤Re≤1000), magnetic field strength (0≤Ha≤80), permeability of porous region (10-4≤Da≤5×10-2), porous layer height (0.15H≤tp≤0.45H), porous layer position (0.25H≤yp≤0.45H), and curvature size (0≤b≤0.3H). The magnetic field reduces the vortex size, while the average Nusselt number of hot walls increases for Ha number above 20 and highest enhancement is 47% for left vertical wall. The variation in the average Nu with permeability of the layer is about 12.5% and 21% for left and right vertical walls, respectively, while these amounts are 12.5% and 32.5% when the location of the porous layer changes. The entropy generation increases with Hartmann number above 20, while there is 22% increase in the entropy generation for the case at the highest magnetic field. The porous layer height reduced the entropy generation for domain above it and it give the highest contribution to the overall entropy generation. When location of the curved porous layer is varied, the highest variation of entropy generation is attained for the domain below it while the lowest value is obtained at yp=0.3H. When the size of elliptic curvature is varied, the overall entropy generation decreases from b=0 to b=0.2H by about 10% and then increases by 5% from b=0.2H to b=0.3H.}, } @article {pmid33510410, year = {2021}, author = {Sato, N and Kawashima, D and Takei, M}, title = {Concentration profiles of ions and particles under hydrodynamic focusing in Y-shaped square microchannel.}, journal = {Scientific reports}, volume = {11}, number = {1}, pages = {2585}, pmid = {33510410}, issn = {2045-2322}, abstract = {Three-dimensional ion and particle concentrations under hydrodynamic focusing in a Y-shaped square microchannel are numerically simulated to clarify the decrease of the ion concentration along the flow direction within the focused particle stream. The simulation model is theoretically governed by the laminar flow and advection-diffusion equations. The governing equations are solved by the finite volume method. The ion and particle concentration distributions at five cross sections after the confluence of the branch channels are analyzed in 30 cases in which the sheath to sample flow rate ratio Qsh/Qsam and the Reynolds number Re are varied as parameters. The results show that the decrease of the cross-sectional average ion concentration along the flow direction within the particle stream [Formula: see text] is described by the diffusion length during the residence time with a characteristic velocity scale. In addition, the deformation of the particle stream due to inertial effects is described by a scaled Reynolds number that is a function of the flow rate ratio. The simulated particle stream thicknesses are validated by theory and a simple experiment. This paper reveals the relationship between the ion and particle concentrations and the dimensionless parameters for hydrodynamic focusing in the Y-shaped square microchannel under typical conditions.}, } @article {pmid33509927, year = {2021}, author = {Andreotti, B and Claudin, P and Iversen, JJ and Merrison, JP and Rasmussen, KR}, title = {A lower-than-expected saltation threshold at Martian pressure and below.}, journal = {Proceedings of the National Academy of Sciences of the United States of America}, volume = {118}, number = {5}, pages = {}, pmid = {33509927}, issn = {1091-6490}, abstract = {Aeolian sediment transport is observed to occur on Mars as well as other extraterrestrial environments, generating ripples and dunes as on Earth. The search for terrestrial analogs of planetary bedforms, as well as environmental simulation experiments able to reproduce their formation in planetary conditions, are powerful ways to question our understanding of geomorphological processes toward unusual environmental conditions. Here, we perform sediment transport laboratory experiments in a closed-circuit wind tunnel placed in a vacuum chamber and operated at extremely low pressures to show that Martian conditions belong to a previously unexplored saltation regime. The threshold wind speed required to initiate saltation is only quantitatively predicted by state-of-the art models up to a density ratio between grain and air of [Formula: see text] but unexpectedly falls to much lower values for higher density ratios. In contrast, impact ripples, whose emergence is continuously observed on the granular bed over the whole pressure range investigated, display a characteristic wavelength and propagation velocity essentially independent of pressure. A comparison of these findings with existing models suggests that sediment transport at low Reynolds number but high grain-to-fluid density ratio may be dominated by collective effects associated with grain inertia in the granular collisional layer.}, } @article {pmid33503087, year = {2021}, author = {Hoeger, K and Ursell, T}, title = {Steric scattering of rod-like swimmers in low Reynolds number environments.}, journal = {Soft matter}, volume = {17}, number = {9}, pages = {2479-2489}, doi = {10.1039/d0sm01551b}, pmid = {33503087}, issn = {1744-6848}, mesh = {*Ecosystem ; Hydrodynamics ; *Models, Biological ; Movement ; Swimming ; }, abstract = {Microbes form integral components of all natural ecosystems. In most cases, the surrounding micro-environment has physical variations that affect the movements of micro-swimmers, including solid objects of varying size, shape and density. As swimmers move through viscous environments, a combination of hydrodynamic and steric forces are known to significantly alter their trajectories in a way that depends on surface curvature. In this work, our goal was to clarify the role of steric forces when rod-like swimmers interact with solid objects comparable to cell size. We imaged hundreds-of-thousands of scattering interactions between swimming bacteria and micro-fabricated pillars with radii from ∼1 to ∼10 cell lengths. Scattering interactions were parameterized by the angle of the cell upon contact with the pillar, and primarily produced forward-scattering events that fell into distinct chiral distributions for scattering angle - no hydrodynamic trapping was observed. The chirality of a scattering event was a stochastic variable whose probability smoothly and symmetrically depended on the contact angle. Neglecting hydrodynamics, we developed a model that only considers contact forces and torques for a rear-pushed thin-rod scattering from a cylinder - the model predictions were in good agreement with measured data. Our results suggest that alteration of bacterial trajectories is subject to distinct mechanisms when interacting with objects of different size; primarily steric for objects below ∼10 cell lengths and requiring incorporation of hydrodynamics at larger scales. These results contribute to a mechanistic framework in which to examine (and potentially engineer) microbial movements through natural and synthetic environments that present complex steric structure.}, } @article {pmid33494348, year = {2021}, author = {Ambreen, T and Saleem, A and Park, CW}, title = {Homogeneous and Multiphase Analysis of Nanofluids Containing Nonspherical MWCNT and GNP Nanoparticles Considering the Influence of Interfacial Layering.}, journal = {Nanomaterials (Basel, Switzerland)}, volume = {11}, number = {2}, pages = {}, doi = {10.3390/nano11020277}, pmid = {33494348}, issn = {2079-4991}, abstract = {The practical implication of nanofluids is essentially dependent on their accurate modelling, particularly in comparison with the high cost of experimental investigations, yet the accuracy of different computational approaches to simulate nanofluids remains controversial to this day. Therefore, the present study is aimed at analysing the homogenous, multiphase Eulerian-Eulerian (volume of fluid, mixture, Eulerian) and Lagrangian-Eulerian approximation of nanofluids containing nonspherical nanoparticles. The heat transfer and pressure drop characteristics of the multiwalled carbon nanotubes (MWCNT)-based and multiwalled carbon nanotubes/graphene nanoplatelets (MWCNT/GNP)-based nanofluids are computed by incorporating the influence of several physical mechanisms, including interfacial nanolayering. The accuracy of tested computational approaches is evaluated by considering particle concentration and Reynolds number ranges of 0.075-0.25 wt% and 200-470, respectively. The results demonstrate that for all nanofluid combinations and operational conditions, the Lagrangian-Eulerian approximation provides the most accurate convective heat transfer coefficient values with a maximum deviation of 5.34% for 0.25 wt% of MWCNT-water nanofluid at the largest Reynolds number, while single-phase and Eulerian-Eulerian multiphase models accurately estimate the thermal fields of the diluted nanofluids at low Reynolds numbers, but overestimate the results for denser nanofluids at high Reynolds numbers.}, } @article {pmid33493237, year = {2021}, author = {Mahrous, SA and Sidik, NAC and Saqr, KM}, title = {Numerical study on the energy cascade of pulsatile Newtonian and power-law flow models in an ICA bifurcation.}, journal = {PloS one}, volume = {16}, number = {1}, pages = {e0245775}, pmid = {33493237}, issn = {1932-6203}, mesh = {Humans ; Intracranial Aneurysm/pathology/*physiopathology ; Kinetics ; *Models, Biological ; *Pulsatile Flow ; }, abstract = {The complex physics and biology underlying intracranial hemodynamics are yet to be fully revealed. A fully resolved direct numerical simulation (DNS) study has been performed to identify the intrinsic flow dynamics in an idealized carotid bifurcation model. To shed the light on the significance of considering blood shear-thinning properties, the power-law model is compared to the commonly used Newtonian viscosity hypothesis. We scrutinize the kinetic energy cascade (KEC) rates in the Fourier domain and the vortex structure of both fluid models and examine the impact of the power-law viscosity model. The flow intrinsically contains coherent structures which has frequencies corresponding to the boundary frequency, which could be associated with the regulation of endothelial cells. From the proposed comparative study, it is found that KEC rates and the vortex-identification are significantly influenced by the shear-thinning blood properties. Conclusively, from the obtained results, it is found that neglecting the non-Newtonian behavior could lead to underestimation of the hemodynamic parameters at low Reynolds number and overestimation of the hemodynamic parameters by increasing the Reynolds number. In addition, we provide physical insight and discussion onto the hemodynamics associated with endothelial dysfunction which plays significant role in the pathogenesis of intracranial aneurysms.}, } @article {pmid33490686, year = {2021}, author = {Ibrahim, W and Hirpho, M}, title = {Finite element analysis of mixed convection flow in a trapezoidal cavity with non-uniform temperature.}, journal = {Heliyon}, volume = {7}, number = {1}, pages = {e05933}, doi = {10.1016/j.heliyon.2021.e05933}, pmid = {33490686}, issn = {2405-8440}, abstract = {A two dimensional flow analysis in a cavity shaped isosceles trapezium is carried out. Non-parallel sides of a trapezium are adiabatic. A varying sinusoidal temperature is applied to the lower wall while the upper wall is at constant temperature. Upper wall of the cavity moves with a velocity η 0 in the positive x-direction. Also, B 0 is constant magnetic field of strength aligned in the same x-direction and Newtonian fluid is considered. The values of magnetic field parameter used are H a = 0 , 50 , the Richardson number is R i = 0.1 , 1 , 10 , R e = 100 is Reynolds number used for the analysis, the amplitude of sinusoidal temperature is m = 0.25 , 0.5 , 1 . The impacts of different leading parameters are analyzed by plotting streamlines for flow fields and isotherm contours for temperature of the flow dynamics. The graphs that signify the variation of average Nusselt number and local Nusselt number are sketched for both lower and upper walls of the cavity. Result indicated that with constant temperature the top wall of the boundary layer thickness decreases as Richardson number Ri increases and for bottom wall with variable temperature. The Nusselt number gets higher with an increment in the amplitude of the oscillation of temperature function. Furthermore, the study revealed that the average Nusselt number gets reduced as the intensity of magnetic field is enhanced. The variation in transit of heat at the bottom wall is similar but the maximum value of heat transfer at the bottom wall shows a variation from 3.8 to 20 when H a = 0 and from 3 to 18 when H a = 50 . The accuracy of the present numerical algorithms is also established.}, } @article {pmid33477950, year = {2021}, author = {Kim, GY and Son, J and Han, JI and Park, JK}, title = {Inertial Microfluidics-Based Separation of Microalgae Using a Contraction-Expansion Array Microchannel.}, journal = {Micromachines}, volume = {12}, number = {1}, pages = {}, pmid = {33477950}, issn = {2072-666X}, support = {NRF-2011-0031348//National Research Foundation of Korea/ ; NRF-2019R1A2B5B03070494//National Research Foundation of Korea/ ; }, abstract = {Microalgae separation technology is essential for both executing laboratory-based fundamental studies and ensuring the quality of the final algal products. However, the conventional microalgae separation technology of micropipetting requires highly skilled operators and several months of repeated separation to obtain a microalgal single strain. This study therefore aimed at utilizing microfluidic cell sorting technology for the simple and effective separation of microalgae. Microalgae are characterized by their various morphologies with a wide range of sizes. In this study, a contraction-expansion array microchannel, which utilizes these unique properties of microalgae, was specifically employed for the size-based separation of microalgae. At Reynolds number of 9, two model algal cells, Chlorella vulgaris (C. vulgaris) and Haematococcus pluvialis (H. pluvialis), were successfully separated without showing any sign of cell damage, yielding a purity of 97.9% for C. vulgaris and 94.9% for H. pluvialis. The result supported that the inertia-based separation technology could be a powerful alternative to the labor-intensive and time-consuming conventional microalgae separation technologies.}, } @article {pmid33465973, year = {2020}, author = {Liu, C and Gayme, DF}, title = {Input-output inspired method for permissible perturbation amplitude of transitional wall-bounded shear flows.}, journal = {Physical review. E}, volume = {102}, number = {6-1}, pages = {063108}, doi = {10.1103/PhysRevE.102.063108}, pmid = {33465973}, issn = {2470-0053}, abstract = {The precise set of parameters governing transition to turbulence in wall-bounded shear flows remains an open question; many theoretical bounds have been obtained, but there is not yet a consensus between these bounds and experimental or simulation results. In this work, we focus on a method to provide a provable Reynolds-number-dependent bound on the amplitude of perturbations a flow can sustain while maintaining the laminar state. Our analysis relies on an input-output approach that partitions the dynamics into a feedback interconnection of the linear and nonlinear dynamics (i.e., a Luré system that represents the nonlinearity as static feedback). We then construct quadratic constraints of the nonlinear term that is restricted by system physics to be energy-conserving (lossless) and to have bounded input-output energy. Computing the region of attraction of the laminar state (set of safe perturbations) and permissible perturbation amplitude are then reformulated as linear matrix inequalities, which allows more computationally efficient solutions than prevailing nonlinear approaches based on the sum of squares programming. The proposed framework can also be used for energy method computations and linear stability analysis. We apply our approach to low-dimensional nonlinear shear flow models for a range of Reynolds numbers. The results from our analytically derived bounds are consistent with the bounds identified through exhaustive simulations. However, they have the added benefit of being achieved at a much lower computational cost and providing a provable guarantee that a certain level of perturbation is permissible.}, } @article {pmid33462593, year = {2021}, author = {Shaheen, S and Anwar Bég, O and Gul, F and Maqbool, K}, title = {Electro-Osmotic Propulsion of Jeffrey Fluid in a Ciliated Channel Under the Effect of Nonlinear Radiation and Heat Source/Sink.}, journal = {Journal of biomechanical engineering}, volume = {143}, number = {5}, pages = {}, doi = {10.1115/1.4049810}, pmid = {33462593}, issn = {1528-8951}, mesh = {*Hot Temperature ; Rheology ; }, abstract = {Mathematical modeling of mechanical system in microfluidics is an emerging area of interest in microscale engineering. Since microfluidic devices use the hair-like structure of artificial cilia for pumping, mixing, and sensing in different fields, electro-osmotic cilia-driven flow helps to generate the fluid velocity for the Newtonian and viscoelastic fluid. Due to the deployment of artificial ciliated walls, the present research reports the combined effect of an electro-osmotic flow and convective heat transfer on Jeffrey viscoelastic electrolytic fluid flow in a two-dimensional ciliated vertical channel. Heat generation/absorption and nonlinear radiation effects are included in the present mathematical model. After applying Debye-Huckel approximation and small Reynolds number approximation to momentum and energy equation, the system of nonlinear partial differential equation is reduced into nonhomogenous boundary value problem. The problem determines the velocity, pressure, and temperature profiles by the application of semi-analytical technique known as homotopy perturbation method (HPM) with the help of software Mathematica. The graphical results of the study suggest that HPM is a reliable methodology for thermo physical electro-osmotic rheological transport in microchannels.}, } @article {pmid33450503, year = {2021}, author = {Javid, K and Riaz, M and Chu, YM and Ijaz Khan, M and Ullah Khan, S and Kadry, S}, title = {Peristaltic activity for electro-kinetic complex driven cilia transportation through a non-uniform channel.}, journal = {Computer methods and programs in biomedicine}, volume = {200}, number = {}, pages = {105926}, doi = {10.1016/j.cmpb.2020.105926}, pmid = {33450503}, issn = {1872-7565}, mesh = {*Body Fluids ; *Cilia ; Kinetics ; Peristalsis ; Viscosity ; }, abstract = {MOTIVATIONS: Now-a-days in medical science, the transport study of biological fluids through non-uniform vessels are going to increase due to their close relation to the reality. Motivated through such type of complex transportation, the current study is presented of cilia hydro-dynamics of an aqueous electrolytic viscous fluid through a non-uniform channel under an applied axial electric field. Mathematical Formulations: Because of the complexity shape and nature of flow channel, we have used curvilinear coordinates in the derivation of continuity and momentum equationsin a fixed frame of reference. A linear transformation is used to renovate the flow system of equations from fixed (laboratory) to moving (wave) frame. For further simplification, the dimensionless variables are introduced to make the flow system of equations into the dimensionless form and at last convert these equations in term of stream function by using the mathematical terminologies of streamlines. The whole analysis is performed under (low Reynolds number) creeping phenomena and long wavelength approximation, respectively. Additionally, small ionic Peclet number and Debye-Huckel linearization are used to simplify the Nernst-Planck and Poisson-Boltzmann equations. The BVP4C technique is used to obtain the numerical solution for velocity distribution, pressure gradient, pressure rise and stream function through MATLAB.

MAIN OUTCOMES: The amplitude of velocity distribution is increased (decreased) at larger values of non-uniform parameter (cilia length). The non-uniform parameter played a vital role not only in the enhancement of circulation at the upper half of the channel but also the length of bolus increased. Results of straight channel are gained for larger value of the dimensionless radius of curvature parameter as well as cilia length.}, } @article {pmid33449773, year = {2020}, author = {Pan, Z and Nunes, JK and Stone, HA}, title = {Regime Map and Triple Point in Selective Withdrawal.}, journal = {Physical review letters}, volume = {125}, number = {26}, pages = {264502}, doi = {10.1103/PhysRevLett.125.264502}, pmid = {33449773}, issn = {1079-7114}, abstract = {Entrainment in selective withdrawal occurs when both the top and bottom phases are withdrawn through a capillary tube oriented perpendicular to a flat gravitationally separated liquid-liquid interface. The tube introduces two distinct features to the conditions for fluid entrainment. First, the ratio of the two phases being withdrawn is affected by the region of influence of the flow upstream of the tube's orifice. Second, a minimum withdrawal flow rate must be reached for entrainment regardless of the distance between the interface and the tube. We show that these phenomena can be understood based on the Reynolds number that governs the external flow field around the capillary tube and the capillary number that regulates the effect of the viscosity and capillarity.}, } @article {pmid33438620, year = {2020}, author = {Shit, GC and Bera, A}, title = {Mathematical model to verify the role of magnetic field on blood flow and its impact on thermal behavior of biological tissue for tumor treatment.}, journal = {Biomedical physics & engineering express}, volume = {6}, number = {1}, pages = {015032}, doi = {10.1088/2057-1976/ab6e22}, pmid = {33438620}, issn = {2057-1976}, mesh = {Blood Flow Velocity ; Computer Simulation ; Hemodynamics ; Humans ; Hyperthermia, Induced/*methods ; *Magnetic Fields ; Microvessels/*pathology ; Models, Biological ; *Models, Theoretical ; Neoplasms/blood supply/*pathology/therapy ; }, abstract = {The numerical computation has been performed to study the effects of static magnetic field on thermal behavior of tumor surrounded by living biological tissues and blood vessels. A small rectangular shaped tumor enclosing the blood vessel surrounded by healthy tissue is considered. The model consists of two-layer composite system in which the microvessel for blood flow is considered as a fluid layer and the living biological tissue including tumor as a solid layer. The wave bioheat transfer equation in the tissue layer together with energy transport equation for blood flow layer has been used in the cylindrical polar coordinates. The analytical expression for blood velocity in the presence of magnetic field has been used from Gold's solution. The computational work has been performed by employing the Crank-Nicolson finite difference method. A comparison has been made to validate our numerical results with the previous solution by setting some parameters. The temperature profiles have been plotted at different locations of the axial tissue length for various values of the Hartmann number, Prandtl number, Womersley number and Reynolds number. It is observed that the application of magnetic field increases heat transfer rate within tumor tissues which in turn attribute to an enhancement of temperature about 316 K or above for hyperthermic treatment in cancer therapy.}, } @article {pmid33430317, year = {2021}, author = {Gnapowski, E and Pytka, J and Józwik, J and Laskowski, J and Michałowska, J}, title = {Wind Tunnel Testing of Plasma Actuator with Two Mesh Electrodes to Boundary Layer Control at High Angle of Attack.}, journal = {Sensors (Basel, Switzerland)}, volume = {21}, number = {2}, pages = {}, pmid = {33430317}, issn = {1424-8220}, abstract = {The manuscript presents experimental research carried out on the wing model with the SD 7003 profile. A plasma actuator with DBD (Dielectric Barrier Discharge) discharges was placed on the wing surface to control boundary layer. The experimental tests were carried out in the AeroLab wind tunnel where the forces acting on the wing during the tests were measured. The conducted experimental research concerns the analysis of the phenomena that take place on the surface of the wing with the DBD plasma actuator turned off and on. The plasma actuator used during the experimental tests has a different structure compared to the classic plasma actuator. The commonly tested plasma actuator uses solid/impermeable electrodes, while in the research, the plasma actuator uses a new type of electrodes, two mesh electrodes separated by an impermeable Kapton dielectric. The experimental research was carried out for the angle of attack α = 15° and several air velocities V = 5-15 m/s with a step of 5 m/s for the Reynolds number Re = 87,500-262,500. The critical angle of attack at which the SD 7003 profile has the maximum lift coefficient is about 11°; during the experimental research, the angle was 15°. Despite the high angle of attack, it was possible to increase the lift coefficient. The use of a plasma actuator with two mesh electrodes allowed to increase the lift by 5%, even at a high angle of attack. During experimental research used high voltage power supply for powering the DBD plasma actuator in the voltage range from 7.5 to 15 kV.}, } @article {pmid33416336, year = {2020}, author = {Monsalve, E and Brunet, M and Gallet, B and Cortet, PP}, title = {Quantitative Experimental Observation of Weak Inertial-Wave Turbulence.}, journal = {Physical review letters}, volume = {125}, number = {25}, pages = {254502}, doi = {10.1103/PhysRevLett.125.254502}, pmid = {33416336}, issn = {1079-7114}, abstract = {We report the quantitative experimental observation of the weak inertial-wave turbulence regime of rotating turbulence. We produce a statistically steady homogeneous turbulent flow that consists of nonlinearly interacting inertial waves, using rough top and bottom boundaries to prevent the emergence of a geostrophic flow. As the forcing amplitude increases, the temporal spectrum evolves from a discrete set of peaks to a continuous spectrum. Maps of the bicoherence of the velocity field confirm such a gradual transition between discrete wave interactions at weak forcing amplitude and the regime described by weak turbulence theory (WTT) for stronger forcing. In the former regime, the bicoherence maps display a near-zero background level, together with sharp localized peaks associated with discrete resonances. By contrast, in the latter regime, the bicoherence is a smooth function that takes values of the order of the Rossby number in line with the infinite-domain and random-phase assumptions of WTT. The spatial spectra then display a power-law behavior, both the spectral exponent and the spectral level being accurately predicted by WTT at high Reynolds number and low Rossby number.}, } @article {pmid33404675, year = {2021}, author = {Klein, AK and Dietzel, A}, title = {A Primer on Microfluidics: From Basic Principles to Microfabrication.}, journal = {Advances in biochemical engineering/biotechnology}, volume = {}, number = {}, pages = {}, pmid = {33404675}, issn = {0724-6145}, abstract = {Microfluidic systems enable manipulating fluids in different functional units which are integrated on a microchip. This chapter describes the basics of microfluidics, where physical effects have a different impact compared to macroscopic systems. Furthermore, an overwiew is given on the microfabrication of these systems. The focus lies on clean-room fabrication methods based on photolithography and soft lithography. Finally, an outlook on advanced maskless micro- and nanofabrication methods is given. Special attention is paid to laser structuring processes.}, } @article {pmid33398321, year = {2021}, author = {Chen, W and Wen, Y and Fan, X and Sun, M and Tian, C and Yang, M and Xie, H}, title = {Magnetically actuated intelligent hydrogel-based child-parent microrobots for targeted drug delivery.}, journal = {Journal of materials chemistry. B}, volume = {9}, number = {4}, pages = {1030-1039}, doi = {10.1039/d0tb02384a}, pmid = {33398321}, issn = {2050-7518}, mesh = {Cells, Cultured ; Child ; Doxorubicin/*chemistry ; *Drug Delivery Systems ; Humans ; Hydrogels/*chemistry ; Lab-On-A-Chip Devices ; Magnetic Phenomena ; Magnetite Nanoparticles/*chemistry ; Particle Size ; *Robotics/instrumentation ; Surface Properties ; }, abstract = {Small intestine-targeted drug delivery by oral administration has aroused the growing interest of researchers. In this work, the child-parent microrobot (CPM) as a vehicle protects the child microrobots (CMs) under a gastric acid environment and releases them in the small intestinal environment. The intelligent hydrogel-based CPMs with sphere, mushroom, red blood cell, and teardrop shapes are fabricated by an extrusion-dripping method. The CPMs package uniform CMs, which are fabricated by designed microfluidic (MF) devices. The fabrication mechanism and tunability of CMs and CPMs with different sizes and shapes are analyzed, modeled, and simulated. The shape of CPM can affect its drug release efficiency and kinetic characteristics. A vision-feedback magnetic driving system (VMDS) actuates and navigates CPM along the predefined path to the destination and continuously releases drug in the simulated intestinal fluid (SIF, a low Reynolds number (Re) regime) using a new motion control method with the tracking-learning-detection (TLD) algorithm. The newly designed CPM combines the advantages of powerful propulsion, good biocompatibility, and remarkable drug loading and release capacity at the intestinal level, which is expected to be competent for oral administration of small intestine-targeted therapy in the future.}, } @article {pmid33396499, year = {2020}, author = {Avila, K and Hof, B}, title = {Second-Order Phase Transition in Counter-Rotating Taylor-Couette Flow Experiment.}, journal = {Entropy (Basel, Switzerland)}, volume = {23}, number = {1}, pages = {}, pmid = {33396499}, issn = {1099-4300}, support = {ZF04B /2019/FB04 Avila_Kerstin//Central Reserach Development Fund of the University of Bremen/ ; }, abstract = {In many basic shear flows, such as pipe, Couette, and channel flow, turbulence does not arise from an instability of the laminar state, and both dynamical states co-exist. With decreasing flow speed (i.e., decreasing Reynolds number) the fraction of fluid in laminar motion increases while turbulence recedes and eventually the entire flow relaminarizes. The first step towards understanding the nature of this transition is to determine if the phase change is of either first or second order. In the former case, the turbulent fraction would drop discontinuously to zero as the Reynolds number decreases while in the latter the process would be continuous. For Couette flow, the flow between two parallel plates, earlier studies suggest a discontinuous scenario. In the present study we realize a Couette flow between two concentric cylinders which allows studies to be carried out in large aspect ratios and for extensive observation times. The presented measurements show that the transition in this circular Couette geometry is continuous suggesting that former studies were limited by finite size effects. A further characterization of this transition, in particular its relation to the directed percolation universality class, requires even larger system sizes than presently available.}, } @article {pmid33362423, year = {2020}, author = {Elsinga, GE and Ishihara, T and Hunt, JCR}, title = {Extreme dissipation and intermittency in turbulence at very high Reynolds numbers.}, journal = {Proceedings. Mathematical, physical, and engineering sciences}, volume = {476}, number = {2243}, pages = {20200591}, pmid = {33362423}, issn = {1364-5021}, abstract = {Extreme dissipation events in turbulent flows are rare, but they can be orders of magnitude stronger than the mean dissipation rate. Despite its importance in many small-scale physical processes, there is presently no accurate theory or model for predicting the extrema as a function of the Reynolds number. Here, we introduce a new model for the dissipation probability density function (PDF) based on the concept of significant shear layers, which are thin regions of elevated local mean dissipation. At very high Reynolds numbers, these significant shear layers develop layered substructures. The flow domain is divided into the different layer regions and a background region, each with their own PDF of dissipation. The volume-weighted regional PDFs are combined to obtain the overall PDF, which is subsequently used to determine the dissipation variance and maximum. The model yields Reynolds number scalings for the dissipation maximum and variance, which are in agreement with the available data. Moreover, the power law scaling exponent is found to increase gradually with the Reynolds numbers, which is also consistent with the data. The increasing exponent is shown to have profound implications for turbulence at atmospheric and astrophysical Reynolds numbers. The present results strongly suggest that intermittent significant shear layer structures are key to understanding and quantifying the dissipation extremes, and, more generally, extreme velocity gradients.}, } @article {pmid33362112, year = {2021}, author = {Foo, CT and Unterberger, A and Menser, J and Mohri, K}, title = {Tomographic imaging using multi-simultaneous measurements (TIMes) for flame emission reconstructions.}, journal = {Optics express}, volume = {29}, number = {1}, pages = {244-255}, doi = {10.1364/OE.412048}, pmid = {33362112}, issn = {1094-4087}, abstract = {The method of tomographic imaging using multi-simultaneous measurements (TIMes) for flame emission reconstructions is presented. Measurements of the peak natural CH* chemiluminescence in the flame and luminescence from different vaporised alkali metal salts that were seeded in a multi-annulus burner were used. An array of 29 CCD cameras around the Cambridge-Sandia burner was deployed, with 3 sets of cameras each measuring a different colour channel using bandpass optical filters. The three-dimensional instantaneous and time-averaged fields of the individual measured channels were reconstructed and superimposed for two new operating conditions, with differing cold flow Reynolds numbers. The contour of the reconstructed flame front followed the interface between the burnt side of the flame, where the alkali salt luminescence appears, and the cold gas region. The increased mixing between different reconstructed channels in the downstream direction that is promoted by the higher levels of turbulence in the larger Reynolds number case was clearly demonstrated. The TIMes method enabled combustion zones originating from different streams and the flame front to be distinguished and their overlap regions to be identified, in the entire volume.}, } @article {pmid33361564, year = {2021}, author = {Brum, J and Bernal, M and Barrere, N and Negreira, C and Cabeza, C}, title = {Vortex dynamics and transport phenomena in stenotic aortic models using Echo-PIV.}, journal = {Physics in medicine and biology}, volume = {66}, number = {5}, pages = {}, doi = {10.1088/1361-6560/abd670}, pmid = {33361564}, issn = {1361-6560}, mesh = {Aortic Valve Stenosis/*diagnostic imaging/physiopathology ; Hemodynamics ; Humans ; *Models, Cardiovascular ; Pulsatile Flow ; *Rheology ; Ultrasonography ; }, abstract = {Atherosclerosis is the most fatal cardiovascular disease. As disease progresses, stenoses grow inside the arteries blocking their lumen and altering blood flow. Analysing flow dynamics can provide a deeper insight on the stenosis evolution. In this work we combined Eulerian and Lagrangian descriptors to analyze blood flow dynamics and fluid transport in stenotic aortic models with morphology, mechanical and optical properties close to those of real arteries. To this end, vorticity, particle residence time (PRT), particle's final position (FP) and finite time Lyapunov's exponents (FTLE) were computed from the experimental fluid velocity fields acquired using ultrasonic particle imaging velocimetry (Echo-PIV). For the experiments, CT-images were used to create morphological realistic models of the descending aorta with 0%, 35% and 50% occlusion degree with same mechanical properties as real arteries. Each model was connected to a circuit with a pulsatile programmable pump which mimics physiological flow and pressure conditions. The pulsatile frequency was set to ≈0.9 Hz (55 bpm) and the upstream peak Reynolds number (Re) was changed from 1100 to 2000. Flow in the post-stenotic region was composed of two main structures: a high velocity jet over the stenosis throat and a recirculation region behind the stenosis where vortex form and shed. We characterized vortex kinematics showing that vortex propagation velocity increases withRe. Moreover, from the FTLE field we identified Lagrangian coherent structures (i.e. material barriers) that dictate transport behind the stenosis. The size and strength of those barriers increased withReand the occlusion degree. Finally, from the PRT and FP maps, we showed that independently ofRe, the same amount of fluid remains on the stenosis over more than a pulsatile period.}, } @article {pmid33352968, year = {2020}, author = {Wu, CY and Lai, BH}, title = {Numerical Study of T-Shaped Micromixers with Vortex-Inducing Obstacles in the Inlet Channels.}, journal = {Micromachines}, volume = {11}, number = {12}, pages = {}, pmid = {33352968}, issn = {2072-666X}, support = {NSC 101 - 2221 - E - 006 - 108 - MY3//Ministry of Science and Technology of the Republic of China on Taiwan/ ; }, abstract = {To enhance fluid mixing, a new approach for inlet flow modification by adding vortex-inducing obstacles (VIOs) in the inlet channels of a T-shaped micromixer is proposed and investigated in this work. We use a commercial computational fluid dynamics code to calculate the pressure and the velocity vectors and, to reduce the numerical diffusion in high-Peclet-number flows, we employ the particle-tracking simulation with an approximation diffusion model to calculate the concentration distribution in the micromixers. The effects of geometric parameters, including the distance between the obstacles and the angle of attack of the obstacles, on the mixing performance of micromixers are studied. From the results, we can observe the following trends: (i) the stretched contact surface between different fluids caused by antisymmetric VIOs happens for the cases with the Reynolds number (Re) greater than or equal to 27 and the enhancement of mixing increases with the increase of Reynolds number gradually, and (ii) the onset of the engulfment flow happens at Re≈125 in the T-shaped mixer with symmetric VIOs or at Re≈140 in the standard planar T-shaped mixer and results in a sudden increase of the degree of mixing. The results indicate that the early initiation of transversal convection by either symmetric or antisymmetric VIOs can enhance fluid mixing at a relatively lower Re.}, } @article {pmid33333847, year = {2020}, author = {Li, YH and Chen, SC}, title = {Propulsion Mechanism of Flexible Microbead Swimmers in the Low Reynolds Number Regime.}, journal = {Micromachines}, volume = {11}, number = {12}, pages = {}, pmid = {33333847}, issn = {2072-666X}, support = {MOST 107-2218-E-606-003-MY2 and MOST 109-2221-E-606-003//Ministry of Science and Technology, Taiwan/ ; }, abstract = {A propulsion mechanism for a flexible microswimmer constructed from superparamagnetic microbeads with different diameters and subjected to an oscillating field was studied experimentally and theoretically herein. Various types of artificial swimmers with different bending patterns were fabricated to determine the flexibility and an effective waveform for a planar beating flagellum. Waveform evolutions for various swimmer configurations were studied to determine the flexible mechanism of the swimmers. A one-armed microswimmer can propel itself only if the friction of its wavelike body is anisotropic. A swimmer with a larger head and a stronger magnetic dipole moment with a flexible tail allows the bending wave to propagate from the head toward the tail to generate forward thrust. The oscillating head and tail do not simultaneously generate positive thrust all the time within a period of oscillation. To increase the propulsion for a bending swimmer, this study proposes a novel configuration for a microbead swimmer that ensures better swimming efficiency. The ratio of the oscillation amplitude of the head to the length of the swimmer (from 0.26 to 0.28) produces a faster swimmer. On the other hand, the swimmer is propelled more effectively if the ratio of the oscillation amplitude of the tail to the length of the swimmer is from 0.29 to 0.33. This study determined the optimal configuration for a flexible microbead swimmer that generates the greatest propulsion in a low Reynolds number environment.}, } @article {pmid33331388, year = {2021}, author = {Dou, Y and Tzelios, PM and Livitz, D and Bishop, KJM}, title = {Programmable topotaxis of magnetic rollers in time-varying fields.}, journal = {Soft matter}, volume = {17}, number = {6}, pages = {1538-1547}, doi = {10.1039/d0sm01443e}, pmid = {33331388}, issn = {1744-6848}, abstract = {We describe how spatially uniform, time-periodic magnetic fields can be designed to power and direct the migration of ferromagnetic spheres up (or down) local gradients in the topography of a solid substrate. Our results are based on a dynamical model that considers the time-varying magnetic torques on the particle and its motion through the fluid at low Reynolds number. We use both analytical theory and numerical simulation to design magnetic fields that maximize the migration velocity up (or down) an inclined plane. We show how "topotaxis" of spherical particles relies on differences in the hydrodynamic resistance to rotation about axes parallel and perpendicular to the plane. Importantly, the designed fields can drive multiple independent particles to move simultaneously in different directions as determined by gradients in their respective environments. Experiments on ferromagnetic spheres provide evidence for topotactic motions up inclined substrates. The ability to program the autonomous navigation of driven particles within anisotropic environments is relevant to the design of colloidal robots.}, } @article {pmid33327115, year = {2020}, author = {Slanina, F}, title = {Colloid particles in microfluidic inertial hydrodynamic ratchet at moderate Reynolds number.}, journal = {Physical review. E}, volume = {102}, number = {5-1}, pages = {052601}, doi = {10.1103/PhysRevE.102.052601}, pmid = {33327115}, issn = {2470-0053}, abstract = {The movement of spherical Brownian particle carried by an alternating fluid flow in a tube of periodically variable diameter is investigated. On the basis of our previous results [Phys. Rev. E 99, 012604 (2019)10.1103/PhysRevE.99.012604] on the hydrodynamics of the problem, we look at the competition of hydrodynamics and diffusion. We use the method of Fick-Jacobs mapping on an effective one-dimensional problem. We calculate the ratchet current and show that is is strictly related to finite size of the particles. The ratchet current grows quadratically with particle radius. We also show that the dominant contribution to the ratchet current is due to inertial hydrodynamic effects. This means that Reynolds number must be at least of order one. We discuss the possible use for separation of particles by size and perspectives of optimization of the tube shape.}, } @article {pmid33325030, year = {2021}, author = {Turon, V and Ollivier, S and Cwicklinski, G and Willison, JC and Anxionnaz-Minvielle, Z}, title = {H2 production by photofermentation in an innovative plate-type photobioreactor with meandering channels.}, journal = {Biotechnology and bioengineering}, volume = {118}, number = {3}, pages = {1342-1354}, doi = {10.1002/bit.27656}, pmid = {33325030}, issn = {1097-0290}, mesh = {Hydrogen/*metabolism ; *Photobioreactors ; Rhodobacter capsulatus/*growth & development ; }, abstract = {Hydrogen production by Rhodobacter capsulatus is an anaerobic, photobiological process requiring specific mixing conditions. In this study, an innovative design of a photobioreactor is proposed. The design is based on a plate-type photobioreactor with an interconnected meandering channel to allow culture mixing and H2 degassing. The culture flow was characterized as a quasi-plug-flow with radial mixing caused by a turbulent-like regime achieved at a low Reynolds number. The dissipated volumetric power was decreased 10-fold while maintaining PBR performances (production and yields) when compared with a magnetically stirred tank reactor. To increase hydrogen production flow rate, several bacterial concentrations were tested by increasing the glutamate concentration using fed-batch cultures. The maximum hydrogen production flow rate (157.7 ± 9.3 ml H2 /L/h) achieved is one of the highest values so far reported for H2 production by R. capsulatus. These first results are encouraging for future scale-up of the plate-type reactor.}, } @article {pmid33322374, year = {2020}, author = {Liu, J and Xiao, Y and Li, M and Tao, J and Xu, S}, title = {Intermittency, Moments, and Friction Coefficient during the Subcritical Transition of Channel Flow.}, journal = {Entropy (Basel, Switzerland)}, volume = {22}, number = {12}, pages = {}, pmid = {33322374}, issn = {1099-4300}, support = {91752203, 11772173, 11490553//National Natural Science Foundation of China/ ; }, abstract = {The intermittent distribution of localized turbulent structures is a key feature of the subcritical transitions in channel flows, which are studied in this paper with a wind channel and theoretical modeling. Entrance disturbances are introduced by small beads, and localized turbulent patches can be triggered at low Reynolds numbers (Re). High turbulence intensity represents strong ability of perturbation spread, and a maximum turbulence intensity is found for every test case as Re ≥ 950, where the turbulence fraction increases abruptly with Re. Skewness can reflect the velocity defects of localized turbulent patches and is revealed to become negative when Re is as low as about 660. It is shown that the third-order moments of the midplane streamwise velocities have minima, while the corresponding forth-order moments have maxima during the transition. These kinematic extremes and different variation scenarios of the friction coefficient during the transition are explained with an intermittent structure model, where the robust localized turbulent structure is simplified as a turbulence unit, a structure whose statistical properties are only weak functions of the Reynolds number.}, } @article {pmid33289747, year = {2021}, author = {Yang, PJ and Lee, AB and Chan, M and Kowalski, M and Qiu, K and Waid, C and Cervantes, G and Magondu, B and Biagioni, M and Vogelnest, L and Martin, A and Edwards, A and Carver, S and Hu, DL}, title = {Intestines of non-uniform stiffness mold the corners of wombat feces.}, journal = {Soft matter}, volume = {17}, number = {3}, pages = {475-488}, doi = {10.1039/d0sm01230k}, pmid = {33289747}, issn = {1744-6848}, mesh = {Animals ; Australia ; Feces ; Fungi ; Intestines ; *Marsupialia ; }, abstract = {The bare-nosed wombat (Vombatus ursinus) is a fossorial, herbivorous, Australian marsupial, renowned for its cubic feces. However, the ability of the wombat's soft intestine to sculpt flat faces and sharp corners in feces is poorly understood. In this combined experimental and numerical study, we show one mechanism for the formation of corners in a highly damped environment. Wombat dissections show that cubes are formed within the last 17 percent of the intestine. Using histology and tensile testing, we discover that the cross-section of the intestine exhibits regions with a two-fold increase in thickness and a four-fold increase in stiffness, which we hypothesize facilitates the formation of corners by contractions of the intestine. Using a mathematical model, we simulate a series of azimuthal contractions of a damped elastic ring composed of alternating stiff and soft regions. Increased stiffness ratio and higher Reynolds number yield shapes that are more square. The corners arise from faster contraction in the stiff regions and relatively slower movement in the center of the soft regions. These results may have applications in manufacturing, clinical pathology, and digestive health.}, } @article {pmid33286895, year = {2020}, author = {Agrawal, R and Ng, HC and Davis, EA and Park, JS and Graham, MD and Dennis, DJC and Poole, RJ}, title = {Low- and High-Drag Intermittencies in Turbulent Channel Flows.}, journal = {Entropy (Basel, Switzerland)}, volume = {22}, number = {10}, pages = {}, pmid = {33286895}, issn = {1099-4300}, support = {FA9550-16-1-0076//Air Force Office of Scientific Research/ ; FA9550-18-1-0174//Air Force Office of Scientific Research/ ; OIA-1832976//National Science Foundation/ ; }, abstract = {Recent direct numerical simulations (DNS) and experiments in turbulent channel flow have found intermittent low- and high-drag events in Newtonian fluid flows, at Reτ=uτh/ν between 70 and 100, where uτ, h and ν are the friction velocity, channel half-height and kinematic viscosity, respectively. These intervals of low-drag and high-drag have been termed "hibernating" and "hyperactive", respectively, and in this paper, a further investigation of these intermittent events is conducted using experimental and numerical techniques. For experiments, simultaneous measurements of wall shear stress and velocity are carried out in a channel flow facility using hot-film anemometry (HFA) and laser Doppler velocimetry (LDV), respectively, for Reτ between 70 and 250. For numerical simulations, DNS of a channel flow is performed in an extended domain at Reτ = 70 and 85. These intermittent events are selected by carrying out conditional sampling of the wall shear stress data based on a combined threshold magnitude and time-duration criteria. The use of three different scalings (so-called outer, inner and mixed) for the time-duration criterion for the conditional events is explored. It is found that if the time-duration criterion is kept constant in inner units, the frequency of occurrence of these conditional events remain insensitive to Reynolds number. There exists an exponential distribution of frequency of occurrence of the conditional events with respect to their duration, implying a potentially memoryless process. An explanation for the presence of a spike (or dip) in the ensemble-averaged wall shear stress data before and after the low-drag (or high-drag) events is investigated. During the low-drag events, the conditionally-averaged streamwise velocities get closer to Virk's maximum drag reduction (MDR) asymptote, near the wall, for all Reynolds numbers studied. Reynolds shear stress (RSS) characteristics during these conditional events are investigated for Reτ = 70 and 85. Except very close to the wall, the conditionally-averaged RSS is higher than the time-averaged value during the low-drag events.}, } @article {pmid33286770, year = {2020}, author = {Kashyap, PV and Duguet, Y and Dauchot, O}, title = {Flow Statistics in the Transitional Regime of Plane Channel Flow.}, journal = {Entropy (Basel, Switzerland)}, volume = {22}, number = {9}, pages = {}, pmid = {33286770}, issn = {1099-4300}, abstract = {The transitional regime of plane channel flow is investigated above the transitional point below which turbulence is not sustained, using direct numerical simulation in large domains. Statistics of laminar-turbulent spatio-temporal intermittency are reported. The geometry of the pattern is first characterized, including statistics for the angles of the laminar-turbulent stripes observed in this regime, with a comparison to experiments. High-order statistics of the local and instantaneous bulk velocity, wall shear stress and turbulent kinetic energy are then provided. The distributions of the two former quantities have non-trivial shapes, characterized by a large kurtosis and/or skewness. Interestingly, we observe a strong linear correlation between their kurtosis and their skewness squared, which is usually reported at much higher Reynolds number in the fully turbulent regime.}, } @article {pmid33286441, year = {2020}, author = {Lee, T}, title = {Lognormality in Turbulence Energy Spectra.}, journal = {Entropy (Basel, Switzerland)}, volume = {22}, number = {6}, pages = {}, pmid = {33286441}, issn = {1099-4300}, abstract = {The maximum entropy principle states that the energy distribution will tend toward a state of maximum entropy under the physical constraints, such as the zero energy at the boundaries and a fixed total energy content. For the turbulence energy spectra, a distribution function that maximizes entropy with these physical constraints is a lognormal function due to its asymmetrical descent to zero energy at the boundary lengths scales. This distribution function agrees quite well with the experimental data over a wide range of energy and length scales. For turbulent flows, this approach is effective since the energy and length scales are determined primarily by the Reynolds number. The total turbulence kinetic energy will set the height of the distribution, while the ratio of length scales will determine the width. This makes it possible to reconstruct the power spectra using the Reynolds number as a parameter.}, } @article {pmid33286423, year = {2020}, author = {Wang, R and Xie, Z and Yin, Y and Chen, L}, title = {Constructal Design of Elliptical Cylinders with Heat Generating for Entropy Generation Minimization.}, journal = {Entropy (Basel, Switzerland)}, volume = {22}, number = {6}, pages = {}, doi = {10.3390/e22060651}, pmid = {33286423}, issn = {1099-4300}, support = {51579244//National Natural Science Foundation of China/ ; }, abstract = {A heat dissipation model of discrete elliptical cylinders with heat generation on a thermal conduction pedestal cooled by forced convection is established. Constructal design is conducted numerically by taking the distributions of thermal conductivity and heat generating intensity as design variables, the dimensionless entropy generation rate (DEGR) as performance indicator. The optimal designs for discrete elliptical cylinders with heat generating are obtained respectively, i.e., there are optimal distributions of heat generating intensity with its fixed total amount of heat sources, and there are optimal distributions of thermal conductivity with its fixed total amount of heat sources. These optimums for minimum DEGRs are different at different Reynolds numbers of airflow. The heat generating intensity can be decreased one by one appropriately in the fluid flow direction to achieve the best effect. When the Reynolds number of airflow is smaller, the thermal conductivity of heat source can be increased one by one appropriately in the fluid flow direction to achieve the best effect; when the Reynolds number of airflow is larger, the thermal conductivity of each heat source should be equalized to achieve the best effect. The results can give thermal design guidelines for the practical heat generating devices with different materials and heat generating intensities.}, } @article {pmid33285959, year = {2020}, author = {Yu, S and Tang, T and Li, J and Yu, P}, title = {Effect of Prandtl Number on Mixed Convective Heat Transfer from a Porous Cylinder in the Steady Flow Regime.}, journal = {Entropy (Basel, Switzerland)}, volume = {22}, number = {2}, pages = {}, doi = {10.3390/e22020184}, pmid = {33285959}, issn = {1099-4300}, support = {11672124//the National Natural Science Foundation of China/ ; ZDSYS201802081843517//Shenzhen Key Laboratory of Complex Aerospace Flows/ ; KQTD2016022620054656//the Shenzhen Peacock Plan/ ; }, abstract = {The effect of the Prandtl number (Pr) on the flow and heat transfer from a porous circular cylinder with internal heat generation in the mixed convection regime is numerically investigated. The steady flow regime is considered over the ranges of the Reynolds number (Re), Darcy number (Da), and Richardson number (Ri), varying from 5 to 40, 10-6 to 10-2, and 0 to 2, respectively. The wake structure, the temperature distribution, and the heat transfer rate are discussed. Besides precipitating the growth of the recirculating wake, the Prandtl number is found to have a significant impact on the thermal characteristics. The concave isotherms, resembling a saddle-shaped structure, occur behind the cylinder at larger Pr, resulting in swells of the isotherms pairing off at the lateral sides. These swells are found to have a negative effect on heat transfer owing to a relatively smaller temperature gradient there. Then, the heat transfer rate in terms of the local Nusselt number (Nu) and enhancement ratio (Er) is calculated, which is closely related to Pr, Re, Da, and Ri. The local minimum heat transfer rate along the cylinder surface is found at the position where the swells of the isotherms form.}, } @article {pmid33285875, year = {2020}, author = {Deriszadeh, A and de Monte, F}, title = {On Heat Transfer Performance of Cooling Systems Using Nanofluid for Electric Motor Applications.}, journal = {Entropy (Basel, Switzerland)}, volume = {22}, number = {1}, pages = {}, doi = {10.3390/e22010099}, pmid = {33285875}, issn = {1099-4300}, abstract = {This paper studies the fluid flow and heat transfer characteristics of nanofluids as advance coolants for the cooling system of electric motors. Investigations are carried out using numerical analysis for a cooling system with spiral channels. To solve the governing equations, computational fluid dynamics and 3D fluid motion analysis are used. The base fluid is water with a laminar flow. The fluid Reynolds number and turn-number of spiral channels are evaluation parameters. The effect of nanoparticles volume fraction in the base fluid on the heat transfer performance of the cooling system is studied. Increasing the volume fraction of nanoparticles leads to improving the heat transfer performance of the cooling system. On the other hand, a high-volume fraction of the nanofluid increases the pressure drop of the coolant fluid and increases the required pumping power. This paper aims at finding a trade-off between effective parameters by studying both fluid flow and heat transfer characteristics of the nanofluid.}, } @article {pmid33285793, year = {2019}, author = {Rasool, G and Zhang, T and Chamkha, AJ and Shafiq, A and Tlili, I and Shahzadi, G}, title = {Entropy Generation and Consequences of Binary Chemical Reaction on MHD Darcy-Forchheimer Williamson Nanofluid Flow Over Non-Linearly Stretching Surface.}, journal = {Entropy (Basel, Switzerland)}, volume = {22}, number = {1}, pages = {}, pmid = {33285793}, issn = {1099-4300}, support = {11771389 and 11621101//The National Science Foundation of China/ ; }, abstract = {The current article aims to present a numerical analysis of MHD Williamson nanofluid flow maintained to flow through porous medium bounded by a non-linearly stretching flat surface. The second law of thermodynamics was applied to analyze the fluid flow, heat and mass transport as well as the aspects of entropy generation using Buongiorno model. Thermophoresis and Brownian diffusion is considered which appears due to the concentration and random motion of nanoparticles in base fluid, respectively. Uniform magnetic effect is induced but the assumption of tiny magnetic Reynolds number results in zero magnetic induction. The governing equations (PDEs) are transformed into ordinary differential equations (ODEs) using appropriately adjusted transformations. The numerical method is used for solving the so-formulated highly nonlinear problem. The graphical presentation of results highlights that the heat flux receives enhancement for augmented Brownian diffusion. The Bejan number is found to be increasing with a larger Weissenberg number. The tabulated results for skin-friction, Nusselt number and Sherwood number are given. A decent agreement is noted in the results when compared with previously published literature on Williamson nanofluids.}, } @article {pmid33285790, year = {2019}, author = {Xu, L and Xiong, Y and Xi, L and Gao, J and Li, Y and Zhao, Z}, title = {Numerical Simulation of Swirling Impinging Jet Issuing from a Threaded Hole under Inclined Condition.}, journal = {Entropy (Basel, Switzerland)}, volume = {22}, number = {1}, pages = {}, doi = {10.3390/e22010015}, pmid = {33285790}, issn = {1099-4300}, support = {51876157//National Natural Science Foundation of China/ ; 2018A030313183//Guangdong Natural Science Foundation/ ; xjj2018044//special fund for basic scientific research business expenses of Central Universities/ ; }, abstract = {There are some inclined jet holes in the cooling structure of the leading edge region of gas turbine blades. In order to improve the cooling effect of traditional round holes, this paper proposes to replace the round holes with threaded holes, and studies the complex flow and heat transfer performance of the swirling impinging jet (SIJ) issuing from the 45° threaded holes in the inclined condition by numerical simulation. The influencing factors include jet inclination angle α (45°-90°), jet-to-plate distance (H/d = 2, 4, 6), and Reynolds number (6000-24,000). The results show that the inclination angle and jet-to-plate distance have a great influence on the size, shape, and position of vortices in the jet space, while the Reynolds number has little effect on the vortices. In the inclined state, the impinging cooling effect of the swirling impinging jet is better than that of the circular impinging jet (CIJ), both heat transfer coefficients will degrade significantly when the inclination angle is 45°. When the inclination angle is greater than 45°, compared with the round hole, the enhanced heat transfer region for the swirling jet is in the region of r/d < 3, while both of the Nusselt numbers in the wall jet region are weak, with a value of just 20. At the same time, with the increasing of the inclination angle (α > 45°), the average Nusselt number on target surface holds a constant value. Under the inclined conditions, the heat transfer coefficient on the target surface for the swirling jet is increased totally with the increasing of the Re, but when the Re is larger than 18,000, the rate of enhanced heat transfer gradually weakens.}, } @article {pmid33285453, year = {2021}, author = {Maurer, L and Villette, C and Reiminger, N and Jurado, X and Laurent, J and Nuel, M and Mosé, R and Wanko, A and Heintz, D}, title = {Distribution and degradation trend of micropollutants in a surface flow treatment wetland revealed by 3D numerical modelling combined with LC-MS/MS.}, journal = {Water research}, volume = {190}, number = {}, pages = {116672}, doi = {10.1016/j.watres.2020.116672}, pmid = {33285453}, issn = {1879-2448}, mesh = {Chromatography, Liquid ; Tandem Mass Spectrometry ; Waste Disposal, Fluid ; Waste Water/analysis ; *Water Pollutants, Chemical/analysis ; *Wetlands ; }, abstract = {Conventional wastewater treatment plants are not designed to treat micropollutants; thus, for 20 years, several complementary treatment systems, such as surface flow wetlands have been used to address this issue. Previous studies demonstrate that higher residence time and low global velocities promote nutrient removal rates or micropollutant photodegradation. Nevertheless, these studies were restricted to the system limits (inlet/outlet). Therefore, detailed knowledge of water flow is crucial for identifying areas that promote degradation and optimise surface flow wetlands. The present study combines 3D water flow numerical modelling and liquid chromatography coupled with high-resolution mass spectrometry (LC-HRMS/MS). Using this numerical model, validated by tracer experimental data, several velocity areas were distinguished in the wetland. Four areas were selected to investigate the waterflow influence and led to the following results: on the one hand, the number and concentration of micropollutants are independent of the waterflow, which could be due to several assumptions, such as the chronic exposure associated with a low Reynolds number; on the other hand, the potential degradation products (metabolites) were also assessed in the sludge to investigate the micropollutant biodegradation processes occurring in the wetland; micropollutant metabolites or degradation products were detected in higher proportions (both number and concentration) in lower flow rate areas. The relation to higher levels of plant and microorganism metabolites suggests higher biological activity that promotes degradation.}, } @article {pmid33268359, year = {2020}, author = {Milana, E and Zhang, R and Vetrano, MR and Peerlinck, S and De Volder, M and Onck, PR and Reynaerts, D and Gorissen, B}, title = {Metachronal patterns in artificial cilia for low Reynolds number fluid propulsion.}, journal = {Science advances}, volume = {6}, number = {49}, pages = {}, pmid = {33268359}, issn = {2375-2548}, abstract = {Cilia are hair-like organelles, present in arrays that collectively beat to generate flow. Given their small size and consequent low Reynolds numbers, asymmetric motions are necessary to create a net flow. Here, we developed an array of six soft robotic cilia, which are individually addressable, to both mimic nature's symmetry-breaking mechanisms and control asymmetries to study their influence on fluid propulsion. Our experimental tests are corroborated with fluid dynamics simulations, where we find a good agreement between both and show how the kymographs of the flow are related to the phase shift of the metachronal waves. Compared to synchronous beating, we report a 50% increase of net flow speed when cilia move in an antiplectic wave with phase shift of -π/3 and a decrease for symplectic waves. Furthermore, we observe the formation of traveling vortices in the direction of the wave when metachrony is applied.}, } @article {pmid33266252, year = {2020}, author = {Morimatsu, H and Tsukahara, T}, title = {Laminar-Turbulent Intermittency in Annular Couette-Poiseuille Flow: Whether a Puff Splits or Not.}, journal = {Entropy (Basel, Switzerland)}, volume = {22}, number = {12}, pages = {}, pmid = {33266252}, issn = {1099-4300}, support = {16H06066, 19H02071//Japan Society for the Promotion of Science/ ; }, abstract = {Direct numerical simulations were carried out with an emphasis on the intermittency and localized turbulence structure occurring within the subcritical transitional regime of a concentric annular Couette-Poiseuille flow. In the annular system, the ratio of the inner to outer cylinder radius is an important geometrical parameter affecting the large-scale nature of the intermittency. We chose a low radius ratio of 0.1 and imposed a constant pressure gradient providing practically zero shear on the inner cylinder such that the base flow was approximated to that of a circular pipe flow. Localized turbulent puffs, that is, axial uni-directional intermittencies similar to those observed in the transitional circular pipe flow, were observed in the annular Couette-Poiseuille flow. Puff splitting events were clearly observed rather far from the global critical Reynolds number, near which given puffs survived without a splitting event throughout the observation period, which was as long as 104 outer time units. The characterization as a directed-percolation universal class was also discussed.}, } @article {pmid33252039, year = {2020}, author = {Asadzadeh, SS and Kiørboe, T and Larsen, PS and Leys, SP and Yahel, G and Walther, JH}, title = {Hydrodynamics of sponge pumps and evolution of the sponge body plan.}, journal = {eLife}, volume = {9}, number = {}, pages = {}, pmid = {33252039}, issn = {2050-084X}, support = {7014-00033B//Danish council for Independent Research/International ; 9278//Villum Fonden/International ; 2016-05446//NSERC/International ; }, mesh = {Animals ; *Biological Evolution ; Hydrodynamics ; Porifera/*anatomy & histology/*physiology ; }, abstract = {Sponges are suspension feeders that filter vast amounts of water. Pumping is carried out by flagellated chambers that are connected to an inhalant and exhalant canal system. In 'leucon' sponges with relatively high-pressure resistance due to a complex and narrow canal system, pumping and filtering are only possible owing to the presence of a gasket-like structure (forming a canopy above the collar filters). Here, we combine numerical and experimental work and demonstrate how sponges that lack such sealing elements are able to efficiently pump and force the flagella-driven flow through their collar filter, thanks to the formation of a 'hydrodynamic gasket' above the collar. Our findings link the architecture of flagellated chambers to that of the canal system, and lend support to the current view that the sponge aquiferous system evolved from an open-type filtration system, and that the first metazoans were filter feeders.}, } @article {pmid33244217, year = {2020}, author = {Arumuru, V and Pasa, J and Samantaray, SS}, title = {Experimental visualization of sneezing and efficacy of face masks and shields.}, journal = {Physics of fluids (Woodbury, N.Y. : 1994)}, volume = {32}, number = {11}, pages = {115129}, pmid = {33244217}, issn = {1070-6631}, abstract = {In the present work, we propose and demonstrate a simple experimental visualization to simulate sneezing by maintaining dynamic similarity to actual sneezing. A pulsed jet with Reynolds number Re = 30 000 is created using compressed air and a solenoid valve. Tracer particles are introduced in the flow to capture the emulated turbulent jet formed due to a sneeze. The visualization is accomplished using a camera and laser illumination. It is observed that a typical sneeze can travel up to 25 ft in ∼22 s in a quiescent environment. This highlights that the present widely accepted safe distance of 6 ft is highly underestimated, especially under the act of a sneeze. Our study demonstrates that a three-layer homemade mask is just adequate to impede the penetration of fine-sized particles, which may cause the spreading of the infectious pathogen responsible for COVID-19. However, a surgical mask cannot block the sneeze, and the sneeze particle can travel up to 2.5 ft. We strongly recommend using at least a three-layer homemade mask with a social distancing of 6 ft to combat the transmission of COVID-19 virus. In offices, we recommend the use of face masks and shields to prevent the spreading of droplets carrying the infectious pathogen. Interestingly, an N-95 mask blocks the sneeze in the forward direction; however, the leakage from the sides and top spreads the sneeze in the backward direction up to 2 ft. We strongly recommend using the elbow or hands to prevent droplet leakage even after wearing a mask during sneezing and coughing.}, } @article {pmid33244213, year = {2020}, author = {Mallik, AK and Mukherjee, S and Panchagnula, MV}, title = {An experimental study of respiratory aerosol transport in phantom lung bronchioles.}, journal = {Physics of fluids (Woodbury, N.Y. : 1994)}, volume = {32}, number = {11}, pages = {111903}, pmid = {33244213}, issn = {1070-6631}, abstract = {The transport and deposition of micrometer-sized particles in the lung is the primary mechanism for the spread of aerosol borne diseases such as corona virus disease-19 (COVID-19). Considering the current situation, modeling the transport and deposition of drops in human lung bronchioles is of utmost importance to determine their consequences on human health. The current study reports experimental observations on deposition in micro-capillaries, representing distal lung bronchioles, over a wide range of Re that imitates the particle dynamics in the entire lung. The experiment investigated deposition in tubes of diameter ranging from 0.3 mm to 2 mm and over a wide range of Reynolds number (10-2 ⩽ Re ⩽ 103). The range of the tube diameter and Re used in this study is motivated by the dimensions of lung airways and typical breathing flow rates. The aerosol fluid was loaded with boron doped carbon quantum dots as fluorophores. An aerosol plume was generated from this mixture fluid using an ultrasonic nebulizer, producing droplets with 6.5 µm as a mean diameter and over a narrow distribution of sizes. The amount of aerosol deposited on the tube walls was measured using a spectrofluorometer. The experimental results show that dimensionless deposition (δ) varies inversely with the bronchiole aspect ratio (L ¯), with the effect of the Reynolds number (Re) being significant only at low L ¯ . δ also increased with increasing dimensionless bronchiole diameter (D ¯), but it is invariant with the particle size based Reynolds number. We show that δ L ¯ ∼ R e - 2 for 10-2 ⩽ Re ⩽ 1, which is typical of a diffusion dominated regime. For Re ⩾ 1, in the impaction dominated regime, δ L ¯ is shown to be independent of Re. We also show a crossover regime where sedimentation becomes important. The experimental results conclude that lower breathing frequency and higher breath hold time could significantly increase the chances of getting infected with COVID-19 in crowded places.}, } @article {pmid33220061, year = {2020}, author = {Battista, NA}, title = {Diving into a Simple Anguilliform Swimmer's Sensitivity.}, journal = {Integrative and comparative biology}, volume = {60}, number = {5}, pages = {1236-1250}, doi = {10.1093/icb/icaa131}, pmid = {33220061}, issn = {1557-7023}, mesh = {Animals ; Biomechanical Phenomena ; Caenorhabditis elegans ; *Locomotion ; *Models, Biological ; Motion ; *Swimming ; }, abstract = {Computational models of aquatic locomotion range from modest individual simple swimmers in 2D to sophisticated 3D multi-swimmer models that attempt to parse collective behavioral dynamics. Each of these models contain a multitude of model input parameters to which its outputs are inherently dependent, that is, various performance metrics. In this work, the swimming performance's sensitivity to parameters is investigated for an idealized, simple anguilliform swimming model in 2D. The swimmer considered here propagates forward by dynamically varying its body curvature, similar to motion of a Caenorhabditis elegans. The parameter sensitivities were explored with respect to the fluid scale (Reynolds number), stroke (undulation) frequency, as well as a kinematic parameter controlling the velocity and acceleration of each upstroke and downstroke. The input Reynolds number and stroke frequencies sampled were from [450, 2200] and [1, 3] Hz, respectively. In total, 5000 fluid-structure interaction simulations were performed, each with a unique parameter combination selected via a Sobol sequence, in order to conduct global sensitivity analysis. Results indicate that the swimmer's performance is most sensitive to variations in its stroke frequency. Trends in swimming performance were discovered by projecting the performance data onto particular 2D subspaces. Pareto-like optimal fronts were identified. This work is a natural extension of the parameter explorations of the same model from Battista in 2020.}, } @article {pmid33212661, year = {2020}, author = {Gungor, A and Hemmati, A}, title = {Wake symmetry impacts the performance of tandem hydrofoils during in-phase and out-of-phase oscillations differently.}, journal = {Physical review. E}, volume = {102}, number = {4-1}, pages = {043104}, doi = {10.1103/PhysRevE.102.043104}, pmid = {33212661}, issn = {2470-0053}, abstract = {The hydrodynamics of two oscillating foils in side-by-side configuration is numerically investigated for in-phase and out-of-phase pitching at Reynolds number of 4000 and Strouhal numbers of St=0.25-0.5. The effects of phase difference (in-phase and out-of-phase) and Strouhal number on symmetric attributes of the wake and unsteady propulsive performance of the foils are studied in detail. At lower Strouhal numbers, there is a quasisteady performance in both thrust generation and power consumption, which coincides with persistence of the wake symmetry. As Strouhal number increases, however, in-phase and out-of-phase pitching display unsteady cycle-averaged behavior with very different wake characteristics. The asymmetric wake of in-phase pitching foils at high Strouhal numbers transitions to a quasisymmetric wake, when an extensive interaction between the two vortex streets is observed in the wake. This coincides with an improvement on the propulsive performance of the foils. In contrast, the symmetric wake of the out-of-phase pitching foils at a high Strouhal number transitions to an asymmetric wake. The adverse effect of this transition is only observed on the propulsive performance of one foil while the other exploits the wake towards a better performance. The collective performance of the the out-of-phase pitching system, however, remains unchanged. There is also a strong correlation between the wake symmetric characteristics and total nonzero side-force production.}, } @article {pmid33212599, year = {2020}, author = {Inubushi, M and Goto, S}, title = {Transfer learning for nonlinear dynamics and its application to fluid turbulence.}, journal = {Physical review. E}, volume = {102}, number = {4-1}, pages = {043301}, doi = {10.1103/PhysRevE.102.043301}, pmid = {33212599}, issn = {2470-0053}, abstract = {We introduce transfer learning for nonlinear dynamics, which enables efficient predictions of chaotic dynamics by utilizing a small amount of data. For the Lorenz chaos, by optimizing the transfer rate, we accomplish more accurate inference than the conventional method by an order of magnitude. Moreover, a surprisingly small amount of learning is enough to infer the energy dissipation rate of the Navier-Stokes turbulence because we can, thanks to the small-scale universality of turbulence, transfer a large amount of the knowledge learned from turbulence data at lower Reynolds number.}, } @article {pmid33211148, year = {2021}, author = {Ikoma, T and Suwa, K and Sano, M and Ushio, T and Saotome, M and Ogawa, N and Satoh, H and Maekawa, Y}, title = {Early changes of pulmonary arterial hemodynamics in patients with systemic sclerosis: flow pattern, WSS, and OSI analysis with 4D flow MRI.}, journal = {European radiology}, volume = {31}, number = {6}, pages = {4253-4263}, pmid = {33211148}, issn = {1432-1084}, support = {26461065//Ministry of Education, Culture, Sports, Science and Technology/ ; }, mesh = {Blood Flow Velocity ; Hemodynamics ; Humans ; *Hypertension, Pulmonary/diagnostic imaging ; Magnetic Resonance Imaging ; Pulmonary Artery/diagnostic imaging ; *Scleroderma, Systemic/complications/diagnostic imaging ; Stress, Mechanical ; }, abstract = {OBJECTIVES: To study the pulmonary artery (PA) hemodynamics in patients with systemic sclerosis (SSc) using 4D flow MRI (4D-flow).

METHODS: Twenty-three patients with SSc (M/F: 2/21, 57 ± 15 years, 3 manifest PA hypertension (PAH) by right heart catheterization) and 10 control subjects (M/F: 1/9, 55 ± 17 years) underwent 4D-flow for the in vivo measurement of 3D blood flow velocities in the PA. Data analysis included area-averaged flow quantification at the main PA, 3D wall shear stress (WSS), oscillatory shear index (OSI) calculation along the PA surface, and Reynolds number. The composite outcome of all-cause death and major adverse cardiac events was also investigated.

RESULTS: The maximum PA flow at the systole did not differ, but the minimum flow at the diastole was significantly greater in patients with SSc compared with that in control subjects (7.7 ± 16.0 ml/s vs. ‑ 13.0 ± 17.3 ml/s, p < 0.01). The maximum WSS at the peak systole was significantly lower and OSI was significantly greater in patients with SSc compared with those in control subjects (maximum WSS: 1.04 ± 0.20 Pa vs. 1.33 ± 0.34 Pa, p < 0.01, OSI: 0.139 ± 0.031 vs. 0.101 ± 0.037, p < 0.01). The cumulative event-free rate for the composite event was significantly lower in patients with minimum flow in main PA ≤ 9.22 ml/s (p = 0.012) and in patients with Reynolds number ≤ 2560 (p < 0.001).

CONCLUSIONS: 4D-flow has the potential to detect changes of PA hemodynamics noninvasively and predict the outcome in patients with SSc at the stage before manifest PAH.

KEY POINTS: • The WSS at the peak systolic phase was significantly lower (p < 0.05), whereas OSI was greater (p < 0.01) in patients with SSc without manifest PAH than in controls. • The hemodynamic change detected by 4D-flow may help patient management even at the stage before manifest PAH in SSc. • The minimum PA flow and Reynolds number by 4D-flow will serve as a predictive marker for SSc.}, } @article {pmid33201951, year = {2021}, author = {Lochab, V and Prakash, S}, title = {Combined electrokinetic and shear flows control colloidal particle distribution across microchannel cross-sections.}, journal = {Soft matter}, volume = {17}, number = {3}, pages = {611-620}, pmid = {33201951}, issn = {1744-6848}, support = {P30 CA016058/CA/NCI NIH HHS/United States ; R01 HL141941/HL/NHLBI NIH HHS/United States ; }, abstract = {Recent experimental observations on combined electrokinetic and shear flows of colloidal suspensions in rectangular cross-section microfluidic channels have shown unusual cross-stream colloidal particle migration and dynamic assembly. Although a new electrophoresis-induced lift force has been postulated to cause the lateral migration of colloidal particles, little is known about how fluid properties and flow conditions impact this force and therefore subsequent colloidal particle migration. Furthermore, no experimental quantification of this electrophoresis-induced lift force is available. We report several key advances by demonstrating that the kinematic viscosity of the fluid can be used to modulate the spatial distribution of particles over the entire microchannel cross-section, with suppression of the colloidal particle migration observed with increase in fluid kinematic viscosity. Colloidal particle migration of ∼10 μm from not only the top and bottom microchannel walls but also from the side walls is shown with the corresponding electrophoresis-induced lift force of up to ∼30 fN. The breadth of flow conditions tested capture the channel Reynolds number in the 0.1-1.1 range, with inertial migration of colloidal particles shown in flow regimes where the migration was previously thought to be ineffective, if not for the electrophoresis-induced lift force. The ability of the electrophoresis-induced lift force to migrate colloidal particles across the entire microchannel cross-section establishes a new paradigm for three-dimensional control of colloidal particles within confined microchannels.}, } @article {pmid33199601, year = {2020}, author = {Omori, T and Ito, H and Ishikawa, T}, title = {Swimming microorganisms acquire optimal efficiency with multiple cilia.}, journal = {Proceedings of the National Academy of Sciences of the United States of America}, volume = {117}, number = {48}, pages = {30201-30207}, pmid = {33199601}, issn = {1091-6490}, mesh = {Bacteria/*metabolism ; Cilia/*physiology ; Hydrodynamics ; Movement ; Rheology ; }, abstract = {Planktonic microorganisms are ubiquitous in water, and their population dynamics are essential for forecasting the behavior of global aquatic ecosystems. Their population dynamics are strongly affected by these organisms' motility, which is generated by their hair-like organelles, called cilia or flagella. However, because of the complexity of ciliary dynamics, the precise role of ciliary flow in microbial life remains unclear. Here, we have used ciliary hydrodynamics to show that ciliates acquire the optimal propulsion efficiency. We found that ciliary flow highly resists an organism's propulsion and that the swimming velocity rapidly decreases with body size, proportional to the power of minus two. Accordingly, the propulsion efficiency decreases as the cube of body length. By increasing the number of cilia, however, efficiency can be significantly improved, up to 100-fold. We found that there exists an optimal number density of cilia, which provides the maximum propulsion efficiency for all ciliates. The propulsion efficiency in this case decreases inversely proportionally to body length. Our estimated optimal density of cilia corresponds to those of actual microorganisms, including species of ciliates and microalgae, which suggests that now-existing motile ciliates and microalgae have survived by acquiring the optimal propulsion efficiency. These conclusions are helpful for better understanding the ecology of microorganisms, such as the energetic costs and benefits of multicellularity in Volvocaceae, as well as for the optimal design of artificial microswimmers.}, } @article {pmid33199599, year = {2020}, author = {Andersen, A and Kiørboe, T}, title = {The effect of tethering on the clearance rate of suspension-feeding plankton.}, journal = {Proceedings of the National Academy of Sciences of the United States of America}, volume = {117}, number = {48}, pages = {30101-30103}, pmid = {33199599}, issn = {1091-6490}, mesh = {Feeding Behavior/*physiology ; Models, Biological ; Plankton/*physiology ; Rheology ; Suspensions ; Swimming ; }, abstract = {Many planktonic suspension feeders are attached to particles or tethered by gravity when feeding. It is commonly accepted that the feeding flows of tethered suspension feeders are stronger than those of their freely swimming counterparts. However, recent flow simulations indicate the opposite, and the cause of the opposing conclusions is not clear. To explore the effect of tethering on suspension feeding, we use a low-Reynolds-number flow model. We find that it is favorable to be freely swimming instead of tethered since the resulting feeding flow past the cell body is stronger, leading to a higher clearance rate. Our result underscores the significance of the near-field flow in shaping planktonic feeding modes, and it suggests that organisms tether for reasons that are not directly fluid dynamical (e.g., to stay near surfaces where the concentration of bacterial prey is high).}, } @article {pmid33197195, year = {2020}, author = {Hatte, S and Pitchumani, R}, title = {Fractal Model for Drag Reduction on Multiscale Nonwetting Rough Surfaces.}, journal = {Langmuir : the ACS journal of surfaces and colloids}, volume = {36}, number = {47}, pages = {14386-14402}, doi = {10.1021/acs.langmuir.0c02790}, pmid = {33197195}, issn = {1520-5827}, abstract = {Rough surfaces in contact with a flow of fluid exhibit alternating no-slip and free shear boundary conditions at the solid-liquid and air-liquid interfaces, respectively, thereby potentially offering drag reduction benefits. The balance between the dynamic pressure in the flow and the restoring capillary pressure in the interasperity spaces determines the stability of the Cassie state of wettability and is a function of the relative extent of no-slip and free shear regions per unit surface area. In the present study, using a fractal representation of rough surface topography, an analytical model is developed to quantify the stability of the Cassie state of wettability as well as drag reduction and the friction factor for laminar flow in a rectangular channel between nonwetting multiscale rough surfaces. A systematic study is conducted to quantify the effects of fractal parameters of the surfaces and the flow Reynolds number on drag reduction and the friction factor. The studies are used to develop friction factor curves extending the classical Moody diagram to hydrophobic and superhydrophobic surfaces. On the basis of the studies, regime maps are derived for estimating the extent of drag reduction offered by hydrophobic and superhydrophobic surfaces, revealing that superhydrophobic surfaces do not always offer the best drag reduction performance. The application of the fractal model to practical topographies of nonwetting surfaces of copper, aluminum, and zinc oxide fabricated via electrodeposition and etching is also discussed.}, } @article {pmid33184652, year = {2020}, author = {Rader, JA and Hedrick, TL and He, Y and Waldrop, LD}, title = {Functional Morphology of Gliding Flight II. Morphology Follows Predictions of Gliding Performance.}, journal = {Integrative and comparative biology}, volume = {60}, number = {5}, pages = {1297-1308}, doi = {10.1093/icb/icaa126}, pmid = {33184652}, issn = {1557-7023}, mesh = {Animals ; Biomechanical Phenomena ; *Birds ; *Flight, Animal ; Models, Biological ; *Wings, Animal ; }, abstract = {The evolution of wing morphology among birds, and its functional consequences, remains an open question, despite much attention. This is in part because the connection between form and function is difficult to test directly. To address this deficit, in prior work, we used computational modeling and sensitivity analysis to interrogate the impact of altering wing aspect ratio (AR), camber, and Reynolds number on aerodynamic performance, revealing the performance landscapes that avian evolution has explored. In the present work, we used a dataset of three-dimensionally scanned bird wings coupled with the performance landscapes to test two hypotheses regarding the evolutionary diversification of wing morphology associated with gliding flight behavior: (1) gliding birds would exhibit higher wing AR and greater chordwise camber than their non-gliding counterparts; and (2) that two strategies for gliding flight exist, with divergent morphological conformations. In support of our first hypothesis, we found evidence of morphological divergence in both wing AR and camber between gliders and non-gliders, suggesting that wing morphology of birds that utilize gliding flight is under different selective pressures than the wings of non-gliding taxa. Furthermore, we found that these morphological differences also yielded differences in coefficient of lift measured both at the maximum lift to drag ratio and at minimum sinking speed, with gliding taxa exhibiting higher coefficient of lift in both cases. Minimum sinking speed was also lower in gliders than non-gliders. However, contrary to our hypothesis, we found that the maximum ratio of the coefficient of lift to the coefficient of drag differed between gliders and non-gliders. This may point to the need for gliders to maintain high lift capability for takeoff and landing independent of gliding performance or could be due to the divergence in flight styles among gliders, as not all gliders are predicted to optimize either quantity. However, direct evidence for the existence of two morphologically defined gliding flight strategies was equivocal, with only slightly stronger support for an evolutionary model positing separate morphological optima for these strategies than an alternative model positing a single peak. The absence of a clear result may be an artifact of low statistical power owing to a relatively small sample size of gliding flyers expected to follow the "aerial search" strategy.}, } @article {pmid33184554, year = {2020}, author = {Lee, JY and Kottke, PA and Fedorov, AG}, title = {Hydrodynamics of Vortical Gas Jets Coupled to Point-Like Suction.}, journal = {Physics of fluids (Woodbury, N.Y. : 1994)}, volume = {32}, number = {10}, pages = {}, pmid = {33184554}, issn = {1070-6631}, support = {R01 GM112662/GM/NIGMS NIH HHS/United States ; }, abstract = {Vortical jet flows in the Reynolds number (Re) range from 1000 to 3425 and swirl number (S) below 0.5, alone and in combination with suction through a small aperture, are experimentally investigated using optical visualization. Schlieren photography is employed to assess the vortical flow structure and establish the fundamental understanding of the source-to-sink gas-dynamic coupling, including the role played by flow rate, jet diameter, and the separation distance between the gas jet source and the suction sink. Compared to vortex-free jets, vortical jets for Re>2700 with swirl number S>0.27 experience earlier laminar-to-turbulent transition, with resulting rapid growth of the jet boundary. The ability to control growth of the jet expansion and mass and momentum dissipation into the surrounding is demonstrated via use of a coaxially aligned flow suction placed in the path of a jet. When a swirling jet is completely coupled with a flow suction, jet expansion is significantly suppressed. The suction/sink flow rate imposes a limit on the maximum input/source flow rate of gas jet to achieve complete coupling. Furthermore, there is a maximum distance over which effective coupling can occur, and for all Reynolds numbers considered this distance is shorter than the distance at which the jet structure breaks up into turbulent eddies in the absence of a sink.}, } @article {pmid33172214, year = {2020}, author = {Astudillo-Castro, C and Cordova, A and Oyanedel-Craver, V and Soto-Maldonado, C and Valencia, P and Henriquez, P and Jimenez-Flores, R}, title = {Prediction of the Limiting Flux and Its Correlation with the Reynolds Number during the Microfiltration of Skim Milk Using an Improved Model.}, journal = {Foods (Basel, Switzerland)}, volume = {9}, number = {11}, pages = {}, pmid = {33172214}, issn = {2304-8158}, support = {11110402//Fondo Nacional de Desarrollo Científico y Tecnológico/ ; }, abstract = {Limiting flux (JL) determination is a critical issue for membrane processing. This work presents a modified exponential model for JL calculation, based on a previously published version. Our research focused on skim milk microfiltrations. The processing variables studied were the crossflow velocity (CFV), membrane hydraulic diameter (dh), temperature, and concentration factor, totaling 62 experimental runs. Results showed that, by adding a new parameter called minimum transmembrane pressure, the modified model not only improved the fit of the experimental data compared to the former version (R2 > 97.00%), but also revealed the existence of a minimum transmembrane pressure required to obtain flux (J). This result is observed as a small shift to the right on J versus transmembrane pressure curves, and this shift increases with the flow velocity. This fact was reported in other investigations, but so far has gone uninvestigated. The JL predicted values were correlated with the Reynolds number (Re) for each dh tested. Results showed that for a same Re; JL increased as dh decreased; in a wide range of Re within the turbulent regime. Finally, from dimensionless correlations; a unique expression JL = f (Re, dh) was obtained; predicting satisfactorily JL (R2 = 84.11%) for the whole set of experiments.}, } @article {pmid33171451, year = {2021}, author = {Ford, MP and Santhanakrishnan, A}, title = {On the role of phase lag in multi-appendage metachronal swimming of euphausiids.}, journal = {Bioinspiration & biomimetics}, volume = {16}, number = {6}, pages = {}, doi = {10.1088/1748-3190/abc930}, pmid = {33171451}, issn = {1748-3190}, mesh = {Biomechanical Phenomena ; *Extremities ; Gait ; *Swimming ; }, abstract = {Metachronal paddling is a common method of drag-based aquatic propulsion, in which a series of swimming appendages are oscillated, with the motion of each appendage phase-shifted relative to the neighboring appendages. Ecologically and economically important euphausiid species such as Antarctic krill (Euphausia superba) swim constantly by stroking their paddling appendages (pleopods), with locomotion accounting for the bulk of their metabolic expenditure. They tailor their swimming gaits for behavioral and energetic needs by changing pleopod kinematics. The functional importance of inter-pleopod phase lag (ϕ) to metachronal swimming performance and wake structure is unknown. To examine this relation, we developed a geometrically and dynamically scaled robot ('krillbot') capable of self-propulsion. Krillbot pleopods were prescribed to mimic published kinematics of fast-forward swimming (FFW) and hovering (HOV) gaits ofE. superba, and the Reynolds number and Strouhal number of the krillbot matched well with those calculated for freely-swimmingE. superba. In addition to examining published kinematics with unevenϕbetween pleopod pairs, we modifiedE. superbakinematics to uniformly varyϕfrom 0% to 50% of the cycle. Swimming speed and thrust were largest for FFW withϕbetween 15%-25%, coincident withϕrange observed in FFW gait ofE. superba. In contrast to synchronous rowing (ϕ= 0%) where distances between hinged joints of adjacent pleopods were nearly constant throughout the cycle, metachronal rowing (ϕ> 0%) brought adjacent pleopods closer together and moved them farther apart. This factor minimized body position fluctuation and augmented metachronal swimming speed. Though swimming speed was lowest for HOV, a ventrally angled downward jet was generated that can assist with weight support during feeding. In summary, our findings show that inter-appendage phase lag can drastically alter both metachronal swimming speed and the large-scale wake structure.}, } @article {pmid33159347, year = {2020}, author = {Ichikawa, C and Ishikawa, D and Yang, JM and Fujii, T}, title = {Phenomenological analysis on whipping behavior of rice flour batter.}, journal = {Journal of food science}, volume = {85}, number = {12}, pages = {4327-4334}, pmid = {33159347}, issn = {1750-3841}, mesh = {Edible Grain/*chemistry ; *Food ; Food Handling ; Oryza/*chemistry ; Particle Size ; Powders ; Surface Tension ; Viscosity ; Wettability ; }, abstract = {In this study, the bubbles in rice flour batter were investigated under a constant temperature, because the bubble size distribution is important for the control of food texture. We obtained experimental data using a hand mixer and compared the properties of doughs prepared using six rice flours; each flour was prepared through a different milling process. We also added the size effect of the rice flour particles as the Bond number. Furthermore, we performed a dynamic wettability test to estimate the wettability of the rice flour surface. The results of this test were described well by the Washburn equation, and dc cosθ/dp was calculated as a wettability parameter (where, dc = effective diameter of a capillary in a powder bed, cosθ = the contact angle, dp = mean particle diameter of rice flour). If bubble sizes depend mainly on the inertial force, viscous force, surface tension, and gravity, then the normalized mean bubble diameter should be a function of the Reynolds number, Weber number, and Froude number. The mean bubble diameter (dbm) generated by whipping was expected to be affected by the thickness (d) of the rod of the mixer, its movement speed, and physical properties of the material. Therefore, dimensionless mean diameter (dbm /d) was expressed based on a dimensionless equation. In the three-phase dispersion, different empirical equations were obtained depending on the amount of rice flour added, and the bubble diameter could be predicted using dimensionless parameters. In addition, the equations were generally applicable to the various materials selected for this study. PRACTICAL APPLICATION: The powder properties of rice flour were investigated, and dimensionless parameters were analyzed to construct an appropriate process control system for rice flour-based food products. Although the process method optimized for flour products is also used for rice flour products in practical situations, the comprehensive evaluation based on dimensionless parameters leads to optimization of the process for rice-flour based products. Moreover, this optimization might strongly support the creation of a new texture, and thus, the potential for market expansion of rice-flour based products is considerable.}, } @article {pmid33158219, year = {2020}, author = {Sana, S and Zivkovic, V and Boodhoo, K}, title = {Empirical Modelling of Hydrodynamic Effects on Starch Nanoparticles Precipitation in a Spinning Disc Reactor.}, journal = {Nanomaterials (Basel, Switzerland)}, volume = {10}, number = {11}, pages = {}, pmid = {33158219}, issn = {2079-4991}, abstract = {Empirical correlations have been developed to relate experimentally determined starch nanoparticle size obtained in a solvent-antisolvent precipitation process with key hydrodynamic parameters of a spinning disc reactor (SDR). Three different combinations of dimensionless groups including a conventional Reynolds number (Re), rotational Reynolds number (Reω) and Rossby number (Ro) have been applied in individual models for two disc surfaces (smooth and grooved) to represent operating variables affecting film flow such as liquid flowrate and disc rotational speed, whilst initial supersaturation (S) has been included to represent varying antisolvent concentrations. Model 1 featuring a combination of Re, Reω and S shows good agreement with the experimental data for both the grooved and smooth discs. For the grooved disc, Re has a greater impact on particle size, whereas Reω is more influential on the smooth disc surface, the difference likely being due to the passive mixing induced by the grooves irrespective of the magnitude of the disc speed. Supersaturation has little impact on particle size within the limited initial supersaturation range studied. Model 2 which characterises both flow rate and disc rotational speed through Ro alone and combined with Re was less accurate in predicting particle size due to several inherent limitations.}, } @article {pmid33157545, year = {2021}, author = {Harvey, C and Inman, DJ}, title = {Aerodynamic efficiency of gliding birds vs comparable UAVs: a review.}, journal = {Bioinspiration & biomimetics}, volume = {16}, number = {3}, pages = {}, doi = {10.1088/1748-3190/abc86a}, pmid = {33157545}, issn = {1748-3190}, mesh = {Animals ; Biomechanical Phenomena ; Birds ; *Flight, Animal ; *Wings, Animal ; }, abstract = {Here, we reviewed published aerodynamic efficiencies of gliding birds and similar sized unmanned aerial vehicles (UAVs) motivated by a fundamental question: are gliding birds more efficient than comparable UAVs? Despite a multitude of studies that have quantified the aerodynamic efficiency of gliding birds, there is no comprehensive summary of these results. This lack of consolidated information inhibits a true comparison between birds and UAVs. Such a comparison is complicated by variable uncertainty levels between the different techniques used to predict avian efficiency. To support our comparative approach, we began by surveying theoretical and experimental estimates of avian aerodynamic efficiency and investigating the uncertainty associated with each estimation method. We found that the methodology used by a study affects the estimated efficiency and can lead to incongruent conclusions on gliding bird aerodynamic efficiency. Our survey showed that studies on live birds gliding in wind tunnels provide a reliable minimum estimate of a birds' aerodynamic efficiency while simultaneously quantifying the wing configurations used in flight. Next, we surveyed the aeronautical literature to collect the published aerodynamic efficiencies of similar-sized, non-copter UAVs. The compiled information allowed a direct comparison of UAVs and gliding birds. Contrary to our expectation, we found that there is no definitive evidence that any gliding bird species is either more or less efficient than a comparable UAV. This non-result highlights a critical need for new technology and analytical advances that can reduce the uncertainty associated with estimating a gliding bird's aerodynamic efficiency. Nevertheless, our survey indicated that species flying within subcritical Reynolds number regimes may inspire UAV designs that can extend their operational range to efficiently operate in subcritical regimes. The survey results provided here point the way forward for research into avian gliding flight and enable informed UAV designs.}, } @article {pmid33156686, year = {2020}, author = {Friedrich, J and Gallon, S and Pumir, A and Grauer, R}, title = {Stochastic Interpolation of Sparsely Sampled Time Series via Multipoint Fractional Brownian Bridges.}, journal = {Physical review letters}, volume = {125}, number = {17}, pages = {170602}, doi = {10.1103/PhysRevLett.125.170602}, pmid = {33156686}, issn = {1079-7114}, abstract = {We propose and test a method to interpolate sparsely sampled signals by a stochastic process with a broad range of spatial and/or temporal scales. To this end, we extend the notion of a fractional Brownian bridge, defined as fractional Brownian motion with a given scaling (Hurst) exponent H and with prescribed start and end points, to a bridge process with an arbitrary number of intermediate and nonequidistant points. Determining the optimal value of the Hurst exponent H_{opt}, appropriate to interpolate the sparse signal, is a very important step of our method. We demonstrate the validity of our method on a signal from fluid turbulence in a high Reynolds number flow and discuss the implications of the non-self-similar character of the signal. The method introduced here could be instrumental in several physical problems, including astrophysics, particle tracking, and specific tailoring of surrogate data, as well as in domains of natural and social sciences.}, } @article {pmid33153075, year = {2020}, author = {Coclite, A and Coclite, GM and De Tommasi, D}, title = {Capsules Rheology in Carreau-Yasuda Fluids.}, journal = {Nanomaterials (Basel, Switzerland)}, volume = {10}, number = {11}, pages = {}, pmid = {33153075}, issn = {2079-4991}, support = {Prin 2017, 267 project code 2017J4EAYB//Ministero dell'Istruzione, dell'Università e della Ricerca/ ; CUP - D94I18000260001//Ministero dell'Istruzione, dell'Università e della Ricerca/ ; }, abstract = {In this paper, a Multi Relaxation Time Lattice Boltzmann scheme is used to describe the evolution of a non-Newtonian fluid. Such method is coupled with an Immersed-Boundary technique for the transport of arbitrarily shaped objects navigating the flow. The no-slip boundary conditions on immersed bodies are imposed through a convenient forcing term accounting for the hydrodynamic force generated by the presence of immersed geometries added to momentum equation. Moreover, such forcing term accounts also for the force induced by the shear-dependent viscosity model characterizing the non-Newtonian behavior of the considered fluid. Firstly, the present model is validated against well-known benchmarks, namely the parabolic velocity profile obtained for the flow within two infinite laminae for five values of the viscosity model exponent, n = 0.25, 0.50, 0.75, 1.0, and 1.5. Then, the flow within a squared lid-driven cavity for Re = 1000 and 5000 (being Re the Reynolds number) is computed as a function of n for a shear-thinning (n < 1) fluid. Indeed, the local decrements in the viscosity field achieved in high-shear zones implies the increment in the local Reynolds number, thus moving the position of near-walls minima towards lateral walls. Moreover, the revolution under shear of neutrally buoyant plain elliptical capsules with different Aspect Ratio (AR = 2 and 3) is analyzed for shear-thinning (n < 1), Newtonian (n = 1), and shear-thickening (n > 1) surrounding fluids. Interestingly, the power law by Huang et al. describing the revolution period of such capsules as a function of the Reynolds number and the existence of a critical value, Rec, after which the tumbling is inhibited in confirmed also for non-Newtonian fluids. Analogously, the equilibrium lateral position yeq of such neutrally buoyant capsules when transported in a plane-Couette flow is studied detailing the variation of yeq as a function of the Reynolds number as well as of the exponent n.}, } @article {pmid33152635, year = {2020}, author = {Kim, J and Jin, D and Choi, H and Kweon, J and Yang, DH and Kim, YH}, title = {A zero-dimensional predictive model for the pressure drop in the stenotic coronary artery based on its geometric characteristics.}, journal = {Journal of biomechanics}, volume = {113}, number = {}, pages = {110076}, doi = {10.1016/j.jbiomech.2020.110076}, pmid = {33152635}, issn = {1873-2380}, mesh = {Blood Flow Velocity ; Constriction, Pathologic ; Coronary Angiography ; *Coronary Stenosis/diagnostic imaging ; *Coronary Vessels/diagnostic imaging ; Humans ; Models, Cardiovascular ; Models, Statistical ; }, abstract = {The diameter- or area-reduction ratio measured from coronary angiography, commonly used in clinical practice, is not accurate enough to represent the functional significance of the stenosis, i.e., the pressure drop across the stenosis. We propose a new zero-dimensional model for the pressure drop across the stenosis considering its geometric characteristics and flow rate. To identify the geometric parameters affecting the pressure drop, we perform three-dimensional numerical simulations for thirty-three patient-specific coronary stenoses. From these numerical simulations, we show that the pressure drop is mostly determined by the curvature as well as the area-reduction ratio of the stenosis before the minimal luminal area (MLA), but heavily depends on the area-expansion ratio after the MLA due to flow separation. Based on this result, we divide the stenosis into the converging and diverging parts in the present zero-dimensional model. The converging part is segmented into a series of straight and curved pipes with curvatures, and the loss of each pipe is estimated by an empirical relation between the total pressure drop, flow rate, and pipe geometric parameters (length, diameter, and curvature). The loss in the diverging part is predicted by a relation among the total pressure drop, Reynolds number, and area expansion ratio with the coefficients determined by a machine learning method. The pressure drops across the stenoses predicted by the present zero-dimensional model agree very well with those obtained from three-dimensional numerical simulations.}, } @article {pmid33147949, year = {2020}, author = {Wang, Y and Zhou, G and Yan, Y and Shao, B and Hou, J}, title = {Construction of Natural Loofah/Poly(vinylidene fluoride) Core-Shell Electrospun Nanofibers via a Controllable Janus Nozzle for Switchable Oil-Water Separation.}, journal = {ACS applied materials & interfaces}, volume = {12}, number = {46}, pages = {51917-51926}, doi = {10.1021/acsami.0c12912}, pmid = {33147949}, issn = {1944-8252}, abstract = {Developing microstructure and multifunctional membranes toward switchable oil-water separation has been highly desired in oily wastewater treatment. Herein, a controllable Janus nozzle was employed to innovatively electrospin natural loofah/poly(vinylidene fluoride) (PVDF) nanofibers with a core-shell structure for gravity-driven water purification. By adjusting flow rates of the PVDF component, a core-shell structure of the composite fibers was obtained caused by the lower viscosity and surface tension of PVDF. In addition, a steady laminar motion of fluids was constructed based on the Reynolds number of flow fields being less than 2300. In order to investigate the formation mechanism of the microstructure, a series of Janus nozzles with different lengths were controlled to study the blending of the two immiscible components. The gravity difference between the two components might cause disturbance of the jet motion, and the PVDF component unidirectionally encapsulated the loofah to form the shell layer. Most importantly, the dry loofah/PVDF membranes could separate oil from an oil-water mixture, while the water-wetted membrane exhibited switchable separation that could separate water from the mixtures because of the hydroxyl groups of the hydrophilic loofah hydrogen-bonding with water molecules and forming a hydration layer. The composite fibers can be applied in water remediation in practice, and the method to produce core-shell structures seems attractive for technological applications involving macroscopic core-shell nano- or microfibers.}, } @article {pmid33136360, year = {2020}, author = {Jeon, W and Ahn, J and Kim, T and Kim, SM and Baik, S}, title = {Intertube Aggregation-Dependent Convective Heat Transfer in Vertically Aligned Carbon Nanotube Channels.}, journal = {ACS applied materials & interfaces}, volume = {12}, number = {45}, pages = {50355-50364}, doi = {10.1021/acsami.0c13361}, pmid = {33136360}, issn = {1944-8252}, abstract = {The heat transfer of carbon nanotube fin geometry has received considerable attention. However, the flow typically occurred over or around the pillars of nanotubes due to the greater flow resistance between the tubes. Here, we investigated the forced convective heat transfer of water through the interstitial space of vertically aligned multiwalled carbon nanotubes (VAMWNTs, intertube distance = 69 nm). The water flow provided significantly a greater Reynolds number (Re) and Nusselt number (Nu) than air flow due to the greater density, heat capacity, and thermal conductivity. However, it resulted in surface tension-induced nanotube aggregation after the flow and drying process, generating random voids in the nanotube channel. This increased permeability (1.27 × 10-11 m2) and Re (2.83 × 10-1) but decreased the heat transfer coefficient (h, 9900 W m-2 K-1) and Nu (53.77), demonstrating a trade-off relationship. The h (25,927 W m-2 K-1) and Nu (153.49) could be further increased, at an equivalent permeability or Re, by increasing nanotube areal density from 2.08 × 1010 to 1.04 × 1011 cm-2. The area-normalized thermal resistance of the densified and aggregated VAMWNTs was smaller than those of the Ni foam, Si microchannel, and carbon nanotube fin array, demonstrating excellent heat transfer characteristics.}, } @article {pmid33119653, year = {2020}, author = {Lyons, K and Murphy, CT and Franck, JA}, title = {Flow over seal whiskers: Importance of geometric features for force and frequency response.}, journal = {PloS one}, volume = {15}, number = {10}, pages = {e0241142}, pmid = {33119653}, issn = {1932-6203}, mesh = {Animals ; Computer Simulation ; *Hydrodynamics ; Phoca/*anatomy & histology ; *Vibration ; Vibrissae/*anatomy & histology ; }, abstract = {The complex undulated geometry of seal whiskers has been shown to substantially modify the turbulent structures directly downstream, resulting in a reduction of hydrodynamic forces as well as modified vortex-induced-vibration response when compared with smooth whiskers. Although the unique hydrodynamic response has been well documented, an understanding of the fluid flow effects from each geometric feature remains incomplete. In this computational investigation, nondimensional geometric parameters of the seal whisker morphology are defined in terms of their hydrodynamic relevance, such that wavelength, aspect ratio, undulation amplitudes, symmetry and undulation off-set can be varied independently of one another. A two-factor fractional factorial design of experiments procedure is used to create 16 unique geometries, each of which dramatically amplifies or attenuates the geometric parameters compared with the baseline model. The flow over each unique topography is computed with a large-eddy simulation at a Reynolds number of 500 with respect to the mean whisker thickness and the effects on force and frequency are recorded. The results determine the specific fluid flow impact of each geometric feature which will inform both biologists and engineers who seek to understand the impact of whisker morphology or lay out a framework for biomimetic design of undulated structures.}, } @article {pmid33095615, year = {2020}, author = {Neuhaus, L and Hölling, M and Bos, WJT and Peinke, J}, title = {Generation of Atmospheric Turbulence with Unprecedentedly Large Reynolds Number in a Wind Tunnel.}, journal = {Physical review letters}, volume = {125}, number = {15}, pages = {154503}, doi = {10.1103/PhysRevLett.125.154503}, pmid = {33095615}, issn = {1079-7114}, abstract = {Generating laboratory flows resembling atmospheric turbulence is of prime importance to study the effect of wind fluctuations on objects such as buildings, vehicles, or wind turbines. A novel driving of an active grid following a stochastic process is used to generate velocity fluctuations with correlation lengths, and, thus, integral scales, much larger than the transverse dimension of the wind tunnel. The combined action of the active grid and a modulation of the fan speed allows one to generate a flow characterized by a four-decade inertial range and an integral scale Reynolds number of 2×10^{7} .}, } @article {pmid33092016, year = {2020}, author = {Domínguez-Pumar, M and Kowalski, L and Jiménez, V and Rodríguez, I and Soria, M and Bermejo, S and Pons-Nin, J}, title = {Analyzing the Performance of a Miniature 3D Wind Sensor for Mars.}, journal = {Sensors (Basel, Switzerland)}, volume = {20}, number = {20}, pages = {}, pmid = {33092016}, issn = {1424-8220}, support = {RTI2018-098728-B-C33//Ministerio de Economía y Competitividad/ ; }, abstract = {This paper analyzes the behavior of a miniature 3D wind sensor designed for Mars atmosphere. The sensor is a spherical structure of 10 mm diameter divided in four sectors. By setting all the sectors to constant temperature, above that of the air, the 3D wind velocity vector can be measured. Two sets of experiments have been performed. First, an experimental campaign made under typical Mars conditions at the Aarhus Wind Tunnel Simulator is presented. The results demonstrate that both wind speed and angle can be efficiently measured, using a simple inverse algorithm. The effect of sudden wind changes is also analyzed and fast response times in the range of 0.7 s are obtained. The second set of experiments is focused on analyzing the performance of the sensor under extreme Martian wind conditions, reaching and going beyond the Dust Devil scale. To this purpose, both high-fidelity numerical simulations of fluid dynamics and heat transfer and experiments with the sensor have been performed. The results of the experiments, made for winds in the Reynolds number 1000-2000 range, which represent 65-130 m/s of wind speed under typical Mars conditions, further confirm the simulation predictions and show that it will be possible to successfully measure wind speed and direction even under these extreme regimes.}, } @article {pmid33076024, year = {2020}, author = {Czelusniak, LE and Mapelli, VP and Guzella, MS and Cabezas-Gómez, L and Wagner, AJ}, title = {Force approach for the pseudopotential lattice Boltzmann method.}, journal = {Physical review. E}, volume = {102}, number = {3-1}, pages = {033307}, doi = {10.1103/PhysRevE.102.033307}, pmid = {33076024}, issn = {2470-0053}, abstract = {One attractive feature of the original pseudopotential method consists on its simplicity of adding a force dependent on a nearest-neighbor potential function. In order to improve the method, regarding thermodynamic consistency and control of surface tension, different approaches were developed in the literature, such as multirange interactions potential and modified forcing schemes. In this work, a strategy to combine these enhancements with an appropriate interaction force field using only nearest-neighbor interactions is devised, starting from the desired pressure tensor. The final step of our procedure is implementing this external force by using the classical Guo forcing scheme. Numerical tests regarding static and dynamic flow conditions were performed. Static tests showed that current procedure is suitable to control the surface tension and phase densities. Based on thermodynamic principles, it is devised a solution for phase densities in a droplet, which states explicitly dependence on the surface tension and interface curvature. A comparison with numerical results suggest a physical inconsistency in the pseudopotential method. This fact is not commonly discussed in the literature, since most of studies are limited to the Maxwell equal area rule. However, this inconsistency is shown to be dependent on the equation of state (EOS), and its effects can be mitigated by an appropriate choice of Carnahan-Starling EOS parameters. Also, a droplet oscillation test was performed, and the most divergent solution under certain flow conditions deviated 7.5% from the expected analytical result. At the end, a droplet impact test against a solid wall was performed to verify the method stability, and it was possible to reach stable simulation results with density ratio of almost 2400 and Reynolds number of Re=373. The observed results corroborate that the proposed method is able to replicate the desired macroscopic multiphase behavior.}, } @article {pmid33076003, year = {2020}, author = {Rana, N and Perlekar, P}, title = {Coarsening in the two-dimensional incompressible Toner-Tu equation: Signatures of turbulence.}, journal = {Physical review. E}, volume = {102}, number = {3-1}, pages = {032617}, doi = {10.1103/PhysRevE.102.032617}, pmid = {33076003}, issn = {2470-0053}, abstract = {We investigate coarsening dynamics in the two-dimensional, incompressible Toner-Tu equation. We show that coarsening proceeds via vortex merger events, and the dynamics crucially depend on the Reynolds number Re. For low Re, the coarsening process has similarities to Ginzburg-Landau dynamics. On the other hand, for high Re, coarsening shows signatures of turbulence. In particular, we show the presence of an enstrophy cascade from the intervortex separation scale to the dissipation scale.}, } @article {pmid33075904, year = {2020}, author = {Bos, WJT and Laadhari, F and Agoua, W}, title = {Linearly forced isotropic turbulence at low Reynolds numbers.}, journal = {Physical review. E}, volume = {102}, number = {3-1}, pages = {033105}, doi = {10.1103/PhysRevE.102.033105}, pmid = {33075904}, issn = {2470-0053}, abstract = {We investigate the forcing strength needed to sustain a flow using linear forcing. A critical Reynolds number R_{c} is determined, based on the longest wavelength allowed by the system, the forcing strength and the viscosity. A simple model is proposed for the dissipation rate, leading to a closed expression for the kinetic energy of the flow as a function of the Reynolds number. The dissipation model and the prediction for the kinetic energy are assessed using direct numerical simulations and two-point closure integrations. An analysis of the dissipation-rate equation and the triadic structure of the nonlinear transfer allows to refine the model in order to reproduce the low-Reynolds-number asymptotic behavior, where the kinetic energy is proportional to R-R_{c} .}, } @article {pmid33075884, year = {2020}, author = {Rinoshika, H and Rinoshika, A and Wang, JJ}, title = {Three-dimensional multiscale flow structures behind a wall-mounted short cylinder based on tomographic particle image velocimetry and three-dimensional orthogonal wavelet transform.}, journal = {Physical review. E}, volume = {102}, number = {3-1}, pages = {033101}, doi = {10.1103/PhysRevE.102.033101}, pmid = {33075884}, issn = {2470-0053}, abstract = {Three-dimensional (3D) flow structures around a wall-mounted short cylinder of height-to-diameter ratio 1 were instantaneously measured by a high-resolution tomographic particle image velocimetry (Tomo-PIV) at Reynolds number of 10 720 in a water tunnel. 3D velocity fields, 3D vorticity, the Q criterion, the rear separation region, and the characteristic of arch type vortex and tip vortices were first discussed. We found a strong 3D W-type arch vortex behind the short cylinder, which was originated by the interaction between upwash and downwash flows. This W-type arch vortex was reshaped to the M-shaped arch vortex downstream. It indicated that the head shape of the arch vortex structure depended on the aspect ratio of the cylinder. The large-scale streamwise vortices were originated by the downwash and upwash flows near the center location of W-type arch vortex. Then the 3D orthogonal wavelet multiresolution technique was developed to analyze instantaneous 3D velocity fields of Tomo-PIV in order to clarify 3D multiscale wake flow structures. The W-type shape arch vortex was extracted in the time-averaged intermediate-scale structure, while an M-shaped arch vortex was identified in the time-averaged large-scale structure. The tip vortices distributed in the time-averaged large- and intermediate-scale structures. The instantaneous intermediate-scale upwash vortices played an essential role in producing W-type head of arch structure. It was also observed that strong small-scale vortices appeared in the shear layer or near the bottom plate and most of them were contained in the intermediate-scale structures.}, } @article {pmid33057044, year = {2020}, author = {Riasat, S and Ramzan, M and Kadry, S and Chu, YM}, title = {Significance of magnetic Reynolds number in a three-dimensional squeezing Darcy-Forchheimer hydromagnetic nanofluid thin-film flow between two rotating disks.}, journal = {Scientific reports}, volume = {10}, number = {1}, pages = {17208}, pmid = {33057044}, issn = {2045-2322}, support = {11971142//National Natural Science Foundation of China/ ; 11871202//National Natural Science Foundation of China/ ; 61673169//National Natural Science Foundation of China/ ; 11701176//National Natural Science Foundation of China/ ; 11626101//National Natural Science Foundation of China/ ; 11601485//National Natural Science Foundation of China/ ; }, abstract = {The remarkable aspects of carbon nanotubes like featherweight, durability, exceptional electrical and thermal conduction capabilities, and physicochemical stability make them desirous materials for electrochemical devices. Having such astonishing characteristics of nanotubes in mind our aspiration is to examine the squeezing three dimensional Darcy-Forchheimer hydromagnetic nanofluid thin-film flow amid two rotating disks with suspended multiwalled carbon nanotubes (MWCNTs) submerged into the base fluid water. The analysis is done by invoking partial slip effect at the boundary in attendance of autocatalytic reactions. The mathematical model consists of axial and azimuthal momentum and magnetic fields respectively. The tangential and axial velocity profiles and components of the magnetic field are examined numerically by employing the bvp4c method for varying magnetic, rotational, and squeezing Reynolds number. The torque effect near the upper and lower disks are studied critically using their graphical depiction. The values of the torque at the upper and lower disks are obtained for rotational and squeezed Reynolds numbers and are found in an excellent concurrence when compared with the existing literature. Numerically it is computed that the torque at the lower disk is higher in comparison to the upper disk for mounting estimates of the squeezed Reynolds number and the dimensionless parameter for magnetic force in an axial direction. From the graphical illustrations, it is learned that thermal profile declines for increasing values of the squeezed Reynolds number.}, } @article {pmid33049170, year = {2020}, author = {Wong, JY and Chan, BKK and Chan, KYK}, title = {Swimming kinematics and hydrodynamics of barnacle larvae throughout development.}, journal = {Proceedings. Biological sciences}, volume = {287}, number = {1936}, pages = {20201360}, pmid = {33049170}, issn = {1471-2954}, mesh = {Animals ; Biomechanical Phenomena ; Extremities ; Hydrodynamics ; Larva/physiology ; Rheology ; Swimming/*physiology ; Thoracica/*physiology ; Zooplankton ; }, abstract = {Changes in size strongly influence organisms' ecological performances. For aquatic organisms, they can transition from viscosity- to inertia-dominated fluid regimes as they grow. Such transitions are often associated with changes in morphology, swimming speed and kinematics. Barnacles do not fit into this norm as they have two morphologically distinct planktonic larval phases that swim differently but are of comparable sizes and operate in the same fluid regime (Reynolds number 100-101). We quantified the hydrodynamics of the rocky intertidal stalked barnacle Capitulum mitella from the nauplius II to cyprid stage and examined how kinematics and size increases affect its swimming performance. Cyprids beat their appendages in a metachronal wave to swim faster, more smoothly, and with less backwards slip per beat cycle than did all naupliar stages. Micro-particle image velocimetry showed that cyprids generated trailing viscous vortex rings that pushed water backwards for propulsion, contrary to the nauplii's forward suction current for particle capture. Our observations highlight that zooplankton swimming performa