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Bibliography on: Reynolds Number

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ESP: PubMed Auto Bibliography 22 Feb 2024 at 01:33 Created: 

Reynolds Number

It is well known that relative size greatly affects how organisms interact with the world. Less well known, at least among biologists, is that at sufficiently small sizes, mechanical interaction with the environment becomes difficult and then virtually impossible. In fluid dynamics, an important dimensionless parameter is the Reynolds Number (abbreviated Re), which is the ratio of inertial to viscous forces affecting the movement of objects in a fluid medium (or the movement of a fluid in a pipe). Since Re is determined mainly by the size of the object (pipe) and the properties (density and viscosity) of the fluid, organisms of different sizes exhibit significantly different Re values when moving through air or water. A fish, swimming at a high ratio of inertial to viscous forces, gives a flick of its tail and then glides for several body lengths. A bacterium, "swimming" in an environment dominated by viscosity, possesses virtually no inertia. When the bacterium stops moving its flagellum, the bacterium "coasts" for about a half of a microsecond, coming to a stop in a distance less than a tenth the diameter of a hydrogen atom. Similarly, the movement of molecules (nutrients toward, wastes away) in the vicinity of a bacterium is dominated by diffusion. Effective stirring — the generation of bulk flow through mechanical means — is impossible at very low Re. An understanding of the constraints imposed by life at low Reynolds numbers is essentially for understanding the prokaryotic biosphere.

Created with PubMed® Query: ( "reynolds number" ) NOT pmcbook NOT ispreviousversion

Citations The Papers (from PubMed®)

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RevDate: 2024-02-21

Chang R, Davydov A, Jaroenlak P, et al (2024)

Energetics of the mokicrosporidian polar tube invasion machinery.

eLife, 12: pii:86638.

Microsporidia are eukaryotic, obligate intracellular parasites that infect a wide range of hosts, leading to health and economic burdens worldwide. Microsporidia use an unusual invasion organelle called the polar tube (PT), which is ejected from a dormant spore at ultra-fast speeds, to infect host cells. The mechanics of PT ejection are impressive. Anncaliia algerae microsporidia spores (3-4 μm in size) shoot out a 100-nm-wide PT at a speed of 300 μm/s, creating a shear rate of 3000 s[-1]. The infectious cargo, which contains two nuclei, is shot through this narrow tube for a distance of ∼60-140 μm (Jaroenlak et al, 2020) and into the host cell. Considering the large hydraulic resistance in an extremely thin tube and the low-Reynolds-number nature of the process, it is not known how microsporidia can achieve this ultrafast event. In this study, we use Serial Block-Face Scanning Electron Microscopy to capture 3-dimensional snapshots of A. algerae spores in different states of the PT ejection process. Grounded in these data, we propose a theoretical framework starting with a systematic exploration of possible topological connectivity amongst organelles, and assess the energy requirements of the resulting models. We perform PT firing experiments in media of varying viscosity, and use the results to rank our proposed hypotheses based on their predicted energy requirement. We also present a possible mechanism for cargo translocation, and quantitatively compare our predictions to experimental observations. Our study provides a comprehensive biophysical analysis of the energy dissipation of microsporidian infection process and demonstrates the extreme limits of cellular hydraulics.

RevDate: 2024-02-20

Qiao S, Cai C, Pan C, et al (2024)

Study on the Performance of a Surface with Coupled Wettability Difference and Convex-Stripe Array for Improved Air Layer Stability.

Langmuir : the ACS journal of surfaces and colloids [Epub ahead of print].

The existence of an air layer reduces friction drag on superhydrophobic surfaces. Therefore, improving the air layer stability of superhydrophobic surfaces holds immense significance in reducing both energy consumption and environmental pollution caused by friction drag. Based on the properties of mathematical discretization and the contact angle hysteresis generated by the wettability difference, a surface coupled with a wettability difference treatment and a convex-stripe array is developed by laser engraving and fluorine modification, and its performance in improving the air layer stability is experimentally studied in a von Kármán swirling flow field. The results show that the destabilization of the air layer is mainly caused by the Kelvin-Helmholtz instability, which is triggered by the density difference between gas and liquid, as well as the tangential velocity difference between gas and liquid. When the air layer is relatively thin, tangential wave destabilization occurs, whereas for larger thicknesses, the destabilization mode is coupled wave destabilization. The maximum Reynolds number that keeps the air layer fully covering the surface of the rotating disk (with drag reduction performance) during the disk rotation process is defined as the critical Reynolds number (Rec), which is 1.62 × 10[5] for the uniform superhydrophobic surface and 3.24 × 10[5] for the superhydrophobic surface with a convex stripe on the outermost ring (SCSSP). Individual treatments of wettability difference and a convex-stripe array on the SCSSP further improve the air layer stability, but Rec remains at 3.24 × 10[5]. Finally, the coupling of the wettability difference treatment with a convex-stripe array significantly improves the air layer stability, resulting in an increase of Rec to 4.05 × 10[5], and the drag reduction rate stably maintained around 30%.

RevDate: 2024-02-20

Dunt T, Heck KS, Lyons K, et al (2024)

Wavelength-induced shedding frequency modulation of seal whisker inspired cylinders.

Bioinspiration & biomimetics [Epub ahead of print].

The spanwise undulated cylinder geometry inspired by seal whiskers has been shown to alter shedding frequency and reduce fluid forces significantly compared to smooth cylindrical geometry. Undulation wavelength is systematically investigated in order to explore its effect on unsteady lift force and shedding frequency. Prior research has parameterized the whisker-inspired geometry and demonstrated the relevance of geometric variations on force reduction properties. Among the geometric parameters, undulation wavelength was identified as a significant contributor to forcing changes. To analyze the effect of undulation wavelength, a thorough investigation isolating changes in wavelength is performed to expand upon previous research that parameterized whisker-inspired geometry and the relevance of geometric variations on the force reduction properties. A set of five whisker-inspired models of varying wavelength are computationally simulated at a Reynolds number of 250 and compared with an equivalent aspect ratio smooth elliptical cylinder. Above a critical nondimensional value, the undulation wavelength reduces the amplitude and frequency of vortex shedding accompanied by a reduction in oscillating lift force. Frequency shedding is tied to the creation of wavelength-dependent vortex structures which vary across the whisker span. These vortices produce distinct shedding modes in which the frequency and phase of downstream structures interact to decrease the oscillating lift forces on the whisker model with particular effectiveness around the wavelength values typically found in nature. The culmination of the these location-based modes produces a complex and spanwise dependent lift frequency spectra at those wavelengths exhibiting maximum force reduction. Understanding the mechanisms of unsteady force reduction and the application of this geometry to vibration tuning and passive flow control for vortex-induced vibration (VIV) reduction.

RevDate: 2024-02-17

Zhou H, EG Blackman (2024)

Helical dynamo growth and saturation at modest versus extreme magnetic Reynolds numbers.

Physical review. E, 109(1-2):015206.

Understanding magnetic field growth in astrophysical objects is a persistent challenge. In stars and galaxies, turbulent flows with net kinetic helicity are believed to be responsible for driving large-scale magnetic fields. However, numerical simulations have demonstrated that such helical dynamos in closed volumes saturate at lower magnetic field strengths when increasing the magnetic Reynolds number Rm. This would imply that helical large-scale dynamos cannot be efficient in astrophysical bodies without the help of helicity outflows such as stellar winds. But do these implications actually apply for very large Rm? Here we tackle the long-standing question of how much helical large-scale dynamo growth occurs independent of Rm in a closed volume. We analyze data from numerical simulations with a new method that tracks resistive versus nonresistive drivers of helical field growth. We identify a presaturation regime when the large-scale field grows at a rate independent of Rm, but to an Rm-dependent magnitude. The latter Rm dependence is due to a dominant resistive contribution, but whose fractional contribution to the large-scale magnetic energy decreases with increasing Rm. We argue that the resistive contribution would become negligible at large Rm and an Rm-independent dynamical contribution would dominate if the current helicity spectrum in the inertial range is steeper than k^{0}. As such helicity spectra are plausible, this renews optimism for the relevance of closed dynamos. Our work pinpoints how modest Rm simulations can cause misapprehension of the Rm→∞ behavior.

RevDate: 2024-02-16

Chen Y, Chong KL, Liu H, et al (2024)

Buoyancy-driven attraction of active droplets.

Journal of fluid mechanics, 980: pii:jfm.2024.18.

For dissolving active oil droplets in an ambient liquid, it is generally assumed that the Marangoni effect results in repulsive interactions, while the buoyancy effects caused by the density difference between the droplets, diffusing product and the ambient fluid are usually neglected. However, it has been observed in recent experiments that active droplets can form clusters due to buoyancy-driven convection (Krüger et al. Eur. Phys. J. E, vol. 39, 2016, pp. 1-9). In this study, we numerically analyze the buoyancy effect, in addition to the propulsion caused by Marangoni flow (with its strength characterized by Péclet number Pe). The buoyancy effects have their origin in (i) the density difference between the droplet and the ambient liquid, which is characterized by Galileo number Ga, and (ii) the density difference between the diffusing product (i.e. filled micelles) and the ambient liquid, which can be quantified by a solutal Rayleigh number Ra. We analyze how the attracting and repulsing behaviour of neighbouring droplets depends on the control parameters Pe, Ga, and Ra. We find that while the Marangoni effect leads to the well-known repulsion between the interacting droplets, the buoyancy effect of the reaction product leads to buoyancy-driven attraction. At sufficiently large Ra, even collisions between the droplets can take place. Our study on the effect of Ga further shows that with increasing Ga, the collision becomes delayed. Moreover, we derive that the attracting velocity of the droplets, which is characterized by a Reynolds number Red, is proportional to Ra[1/4]/(ℓ/R), where ℓ/R is the distance between the neighbouring droplets normalized by the droplet radius. Finally, we numerically obtain the repulsive velocity of the droplets, characterized by a Reynolds number Rerep, which is proportional to PeRa[-0.38]. The balance of attractive and repulsive effect leads to Pe ~ Ra[0.63], which agrees well with the transition curve between the regimes with and without collision.

RevDate: 2024-02-15

Xi Y, F Meng (2024)

Numerical study on flow and heat transfer characteristics of rectangular mini-channel of interpolated double S turbulators.

PloS one, 19(2):e0297678 pii:PONE-D-23-35780.

In this study, we propose a new type of small-channel plug-in, the double S turbulators, for passive heat transfer enhancement to improve the flow and heat transfer performance of the fluid in the channel. In the range of Reynolds number 254.51~2545.09, under constant wall temperature heating conditions, the effects of interpolated double S turbulators with different long axial radii (1mm, 1.5mm, 2mm) on the average Nusselt number, pressure drop, total thermal resistance and field synergy number in the rectangular mini-channel were studied. The simulation results show that compared with the smooth rectangular mini-channel, after interpolating double S turbulators with different long axial radii (1mm, 1.5mm, 2mm), the average Nusselt number increased by 81.74%~101.74%, 71.29%~94.06%, 67.16%~88.48%, the total thermal resistance decreased by 45.1%~50.72%, 41.72%~48.74%, 40.28%~47.2%, and the number of field synergies increased by 85.58%~111.65%, 74.1%~102.6%, 69.64%~96.12%. At present, there are few studies on the boundary condition of constant wall temperature, and this paper supplements the research on this aspect. At the same time, the heat transfer performance of the rectangular mini-channel of the interpolated double S turbulators is stronger than that of the ordinary smooth rectangular mini-channel, which not only provides a new idea for the manufacture of micro heat dissipation equipment, but also improves the heat transfer performance of micro heat dissipation equipment and improves its work efficiency. According to the simulation data, the prediction formula of average Nusselt number and pressure drop was established by nonlinear regression method, which can be used to predict the flow and heat transfer characteristics of the rectangular mini-channel of the interpolated double S turbulators.

RevDate: 2024-02-14

Gnanasekaran M, A Satheesh (2024)

Numerical analysis of turbulent flow characteristics with the influence of speed ratio in a double-sided cavity.

MethodsX, 12:102594.

The present study numerically investigates the two-dimensional steady incompressible turbulent flow characteristics in an enclosed cavity. The finite volume method (FVM) is used to discretize the governing equations, and k-ε turbulence models are adopted to predict the flow characteristics. The turbulent flow behavior is studied by varying the speed ratio (0.05 ≤ S ≤ 1.0), aspect ratio (0.5 ≤ K ≤ 2.0), and Reynolds number (1 × 10[4] ≤ Re ≤ 2 × 10[5]). The flow characteristics are analyzed using stream function (ψ), Reynolds stresses (u'v'), and turbulent quantities. Results show the Reynolds number and speed ratio significantly influence the formation of vortices over the selected range of operating parameters. With the speed ratio, the turbulent kinetic energy reduces considerably by increasing the Reynolds number and aspect ratio. Similarly, for S = 0.05 and K = 0.5, the turbulent kinetic energy and dissipation rate are decreased by 89.16% and 42.28%, respectively. When Re is increased from 1 × 10[4] to 2 × 10[5], the turbulent viscosity increases by 92.10%. By comparing the results, average turbulent quantities are decreased by increasing the flow parameters.•Turbulent flow behavior is investigated by using the FVM near-wall treatment approach.One of the unique parameters called speed ratio is emphasized.•Contours of turbulence kinetic energy, dissipation, and viscosity are examined.•The average intensity of turbulent quantities is decreased by increasing the speed ratio.

RevDate: 2024-02-09

Kim SJ, Kos Ž, Um E, et al (2024)

Symmetrically pulsating bubbles swim in an anisotropic fluid by nematodynamics.

Nature communications, 15(1):1220.

Swimming in low-Reynolds-number fluids requires the breaking of time-reversal symmetry and centrosymmetry. Microswimmers, often with asymmetric shapes, exhibit nonreciprocal motions or exploit nonequilibrium processes to propel. The role of the surrounding fluid has also attracted attention because viscoelastic, non-Newtonian, and anisotropic properties of fluids matter in propulsion efficiency and navigation. Here, we experimentally demonstrate that anisotropic fluids, nematic liquid crystals (NLC), can make a pulsating spherical bubble swim despite its centrosymmetric shape and time-symmetric motion. The NLC breaks the centrosymmetry by a deformed nematic director field with a topological defect accompanying the bubble. The nematodynamics renders the nonreciprocity in the pulsation-induced fluid flow. We also report speed enhancement by confinement and the propulsion of another symmetry-broken bubble dressed by a bent disclination. Our experiments and theory propose another possible mechanism of moving bodies in complex fluids by spatiotemporal symmetry breaking.

RevDate: 2024-02-09

Wang Z, Liu X, Guo Y, et al (2024)

Armored Superhydrophobic Surfaces with Excellent Drag Reduction in Complex Environmental Conditions.

Langmuir : the ACS journal of surfaces and colloids [Epub ahead of print].

Superhydrophobic surfaces (SHSs) have possibilities for achieving significantly reduced solid-liquid frictional drag in the marine sector due to their excellent water-repelling properties. Although the stability of SHSs plays a key role in drag reduction, little consideration was given to the effect of extreme environments on the ability of SHSs to achieve drag reduction underwater, particularly when subjected to acidic conditions. Here, we propose interconnected microstructures to protect superhydrophobic coatings with the aim of enhancing the stability of SHSs in extreme environments. The stability of armored SHSs (ASHSs) was demonstrated by the contact angle and bounce time of droplets on superhydrophobic surfaces treated by various methods, resulting in an ASHS surface with excellent stability under extreme environmental conditions. Additionally, inspired by microstructures protecting superhydrophobic nanomaterials from frictional wear, the armored superhydrophobic spheres (ASSPs) were designed to explain from theoretical and experimental perspectives why ASSPs can achieve sustainable drag reduction and demonstrate that the ASSPs can achieve drag reduction of over 90.4% at a Reynolds number of 6.25 × 10[4] by conducting water entry experiments on spheres treated in various solutions. These studies promote a fundamental understanding of what drives the application of SHSs under extreme environmental conditions and provide practical strategies to maximize frictional drag reduction.

RevDate: 2024-02-09

Wang K, Sprinkle B, Zuo M, et al (2024)

Centrifugal Flows Drive Reverse Rotation of Feynman's Sprinkler.

Physical review letters, 132(4):044003.

The issue of reversibility in hydromechanical sprinklers that auto-rotate while ejecting fluid from S-shaped tubes raises fundamental questions that remain unresolved. Here, we report on precision experiments that reveal robust and persistent reverse rotation under suction and a model that accounts for the observed motions. We implement an ultralow friction bearing in an apparatus that allows for free rotation under ejection and suction for a range of flow rates and arbitrarily long times. Flow measurements reveal a rocketlike mechanism shared by the reverse and forward modes that involves angular momentum flux, whose subtle manifestation in the reverse case stems from centrifugal effects for flows in curved conduits. These findings answer Feynman's long-standing question by providing quantitatively accurate explanations of both modes, and they suggest further inquiries into flux-based force generation and the roles of geometry and Reynolds number.

RevDate: 2024-02-07

Mishra NK, Sharma P, Sharma BK, et al (2024)

Electroosmotic MHD ternary hybrid Jeffery nanofluid flow through a ciliated vertical channel with gyrotactic microorganisms: Entropy generation optimization.

Heliyon, 10(3):e25102 pii:S2405-8440(24)01133-2.

In this study, the computational analysis of entropy generation optimization for synthetic cilia regulated ternary hybrid Jeffery nanofluid (Ag-Au-TiO2/PVA) flow through a peristaltic vertical channel with swimming motile Gyrotactic microorganisms is investigated. Understanding the intricate interaction of multiple physical phenomena in biomedical applications is essential for optimizing entropy generation and advancing microfluidic systems. The characteristics of nanofluid are explored for the electroosmotic MHD fluid flow in the presence of thermophoresis and Brownian motion, viscous dissipation, Ohmic heating and chemical reaction. Using the appropriate transformations, a set of ordinary differential equations are created from the governing partial differential equations. The resulting ODEs are numerically solved using the shooting technique using BVP5C in MATLAB after applying the long-wavelength and low Reynolds number approximation. The velocity, temperature, concentration, electroosmosis, and microorganism density profiles are analyzed graphically for different emerging parameters. Graphical investigation of engineering interest quantities like heat transfer rate, mass transfer rate, skin friction coefficient, and entropy generation optimization are also presented. It is observed that the rate of mass transfer increases for increasing thermophoretic parameter, while reverse effect is noted for Brownian motion parameter, Schmidt number, and chemical reaction number. The outcomes of present study can be pertinent in studying Cilia properties of respiratory tract, reproductive system, and brain ventricles.

RevDate: 2024-02-07

Selimefendigil F, Ghachem K, Albalawi H, et al (2024)

Magneto-convection of nanofluid flow over multiple rotating cylinders in a confined space with elastic walls and ventilated ports.

Heliyon, 10(3):e25101 pii:S2405-8440(24)01132-0.

In this study, convective heat transfer for nanofluid flow over multiple rotating cylinder in a confined space is analyzed under magnetic field while enclosure has one inlet and one outlet port. Three identical circular cylinder are used and the two walls of the cavity are considered to be elastic. The coupled fluid-structure interaction and magneto-convection problem is solved by finite element method. Impacts of rotational Reynolds number (Rew between -100 and 100), Hartmann number (Ha between 0 and 50), cylinder size (R between 0.001H and 0.11H) and Cauchy number (Ca between 10-8 and 10-3) on the flow and thermal performance features are explored. The flow field and recirculation inside the cavity are significantly affected by the activation of rotation and magnetic field. The vortices are suppressed by increasing the strength of magnetic field and thermal performance is improved. Thermal performance of 56.6% is achieved by activation of magnetic field at the highest strength with rotations of the circular cylinders. When rotations are active, heat transfer rate is reduced while up to 40% reduction is obtained without magnetic field. Cylinder size has the highest impact on the overall thermal performance improvement while up to 132% enhancements are achieved. The contribution of elastic walls on the thermal performance is slight while less than 5% improvements in the average heat transfer is obtained. An optimization study leads to 12.7% higher thermal performance improvements as compared to best case of parametric computational fluid dynamics simulation results while the optimum values of (Rew, Ha, R) is obtained as (-80.66, 50, 0.11H).

RevDate: 2024-02-06

Massaro D, Karp M, Jansson N, et al (2024)

Direct numerical simulation of the turbulent flow around a Flettner rotor.

Scientific reports, 14(1):3004.

The three-dimensional turbulent flow around a Flettner rotor, i.e. an engine-driven rotating cylinder in an atmospheric boundary layer, is studied via direct numerical simulations (DNS) for three different rotation speeds ([Formula: see text]). This technology offers a sustainable alternative mainly for marine propulsion, underscoring the critical importance of comprehending the characteristics of such flow. In this study, we evaluate the aerodynamic loads produced by the rotor of height h, with a specific focus on the changes in lift and drag force along the vertical axis of the cylinder. Correspondingly, we observe that vortex shedding is inhibited at the highest [Formula: see text] values investigated. However, in the case of intermediate [Formula: see text], vortices continue to be shed in the upper section of the cylinder ([Formula: see text]). As the cylinder begins to rotate, a large-scale motion becomes apparent on the high-pressure side, close to the bottom wall. We offer both a qualitative and quantitative description of this motion, outlining its impact on the wake deflection. This finding is significant as it influences the rotor wake to an extent of approximately one hundred diameters downstream. In practical applications, this phenomenon could influence the performance of subsequent boats and have an impact on the cylinder drag, affecting its fuel consumption. This fundamental study, which investigates a limited yet significant (for DNS) Reynolds number and explores various spinning ratios, provides valuable insights into the complex flow around a Flettner rotor. The simulations were performed using a modern GPU-based spectral element method, leveraging the power of modern supercomputers towards fundamental engineering problems.

RevDate: 2024-02-02

Mandujano F, E Vázquez-Luis (2024)

Chaotic vortex-induced rotation of an elliptical cylinder.

Chaos (Woodbury, N.Y.), 34(2):.

Non-linear oscillations of an elliptical cylinder, which can rotate about an axis that passes through its symmetry axle due to a torsional spring and hydrodynamic torque produced by the flow of a Newtonian fluid, were analyzed in terms of a single parameter that compares vortex shedding frequency with the torsional spring's natural frequency. The governing equations for the flow coupled with a rigid body with one degree of freedom were solved numerically using the lattice-Boltzmann method. The Reynolds number used was Re=200, which, in the absence of torsional spring, produces chaotic oscillations of the elliptical cylinder. When the torsional spring is included, we identified three branches separated by transition regions when stiffness of the restorative torque changes, as in the case of vortex-induced vibrations. However, in this case, several regions presenting chaotic dynamics were identified. Two regions with stable limit cycles were found when both torques synchronized and when stiffness of the torsional spring is big enough so that the ellipse's oscillation is small.

RevDate: 2024-02-01

Ashkani A, Jafari A, Ghomsheh MJ, et al (2024)

Enhancing particle focusing: a comparative experimental study of modified square wave and square wave microchannels in lift and Dean vortex regimes.

Scientific reports, 14(1):2679.

Serpentine microchannels are known for their effective particle focusing through Dean flow-induced rotational effects, which are used in compact designs for size-dependent focusing in medical diagnostics. This study explores square serpentine microchannels, a geometry that has recently gained prominence in inertial microfluidics, and presents a modification of square wave microchannels for improved particle separation and focusing. The proposed modification incorporates an additional U-shaped unit to convert the square wave microchannel into a non-axisymmetric structure, which enhances the Dean flow and consequently increases the Dean drag force. Extensive experiments were conducted covering a wide range of Reynolds numbers and particle sizes (2.45 µm to 12 µm). The particle concentration capability and streak position dynamics of the two structures were compared in detail. The results indicate that the modified square-wave microchannel exhibits efficient particle separation in the lower part of the Dean vortex-dominated regime. With increasing Reynolds number, the particles are successively focused into two streaks in the lift force-dominated regime and into a single streak in the Dean vortex-dominated regime, in this modified square wave geometry. These streaks have a low standard deviation around a mean value. In the Dean vortex-dominated regime, the location of the particle stream is highly dependent on the particle size, which allows good particle separation. Particle focusing occurs at lower Reynolds numbers in both the lift-dominated and lift/Dean drag-dominated regions than in the square wave microchannel. The innovative serpentine channel is particularly useful for the Dean drag-dominated regime and introduces a unique asymmetry that affects the particle focusing dynamics. The proposed device offers significant advantages in terms of efficiency, parallelization, footprint, and throughput over existing geometries.

RevDate: 2024-02-01

Xia Y, S Lyu (2024)

Direct numerical simulation of contaminant removal in presence of underfloor air distribution system.

Heliyon, 10(2):e24331 pii:S2405-8440(24)00362-1.

Indoor contaminant removal over 0.5 ≤ FrT ≤ 5.0, 0.5 ≤ N ≤ 5.0, and 50 ≤ Re ≤ 500 was investigated numerically, wherein FrT refers to the Froude number, N refers to the buoyancy ratio, and Re refers to the Reynolds number. As demonstrated, the ventilation effectiveness increased with increasing contaminant source intensity and air supply intensity at a constant air temperature, indicating that increase the fresh air can effectively eliminate contaminants in this case. At high air supply temperatures, the heat retention time and contaminant transport was extremely short, and the fresh air induced by strong natural convection floating lift was rapidly discharged. Additioanlly, the air supply intensity had significant effects on contaminant removal. Quantification of the ventilation effectiveness under the combined effects of air supply intensity, air supply temperature and contaminant source intensity was determined based on the results of direct numerical simulations.

RevDate: 2024-02-01

Almutairi DK (2024)

Mathematical modelling and heat transfer observations for Jeffrey nanofluid with applications of extended Fourier theory and temperature dependent thermal conductivity.

Heliyon, 10(2):e24353 pii:S2405-8440(24)00384-0.

The suspension of non-Newtonian materials with nanoparticles is important to enhance the thermal phenomenon in various engineering and industrial processes. The versatile research in nanomaterials provide different applications in thermal processes, heat exchangers, thermoelectric devices, HVAC systems, energy processes etc. Following to such novel motivations in mind, current research endorsed the enhancement in heat transfer due to suspension of Jeffrey nanofluid comprising the variable thermal conductivity. The cause of flow is associated to two disks attaining fixed distance. The modified developed relations for Fourier's hypothesis are utilized to model the problem. The flow problem is modeled with appliance of fundamental novel laws. By applying suitable transformations, corresponding differential equations are renovated into dimensionless forms which are solved with applications of analytic homotopic algorithm. The behavior of temperature and velocity due to various parameters is discussed. The numerical calculations have been done for wall shear force and Nusselt number. The results show that the velocity profile boosted due to variation of stretching ratio constant. The enhancement in heat transfer is observed due to Reynolds number. Moreover, the increasing observations for wall shear force in upper and lower disk surfaces are obtained against larger material parameter. The simulated results may find applications in improving heat transfer phenomenon, manufacturing systems, recovery processes, cooling systems, chemical phenomenon, fuel cells etc.

RevDate: 2024-02-01

Gande VV, Podupu PKR, Berry B, et al (2024)

Engineering advancements in microfluidic systems for enhanced mixing at low Reynolds numbers.

Biomicrofluidics, 18(1):011502 pii:5.0178939.

Mixing within micro- and millichannels is a pivotal element across various applications, ranging from chemical synthesis to biomedical diagnostics and environmental monitoring. The inherent low Reynolds number flow in these channels often results in a parabolic velocity profile, leading to a broad residence time distribution. Achieving efficient mixing at such small scales presents unique challenges and opportunities. This review encompasses various techniques and strategies to evaluate and enhance mixing efficiency in these confined environments. It explores the significance of mixing in micro- and millichannels, highlighting its relevance for enhanced reaction kinetics, homogeneity in mixed fluids, and analytical accuracy. We discuss various mixing methodologies that have been employed to get a narrower residence time distribution. The role of channel geometry, flow conditions, and mixing mechanisms in influencing the mixing performance are also discussed. Various emerging technologies and advancements in microfluidic devices and tools specifically designed to enhance mixing efficiency are highlighted. We emphasize the potential applications of micro- and millichannels in fields of nanoparticle synthesis, which can be utilized for biological applications. Additionally, the prospects of machine learning and artificial intelligence are offered toward incorporating better mixing to achieve precise control over nanoparticle synthesis, ultimately enhancing the potential for applications in these miniature fluidic systems.

RevDate: 2024-01-31

Shi Q, Wu J, Chen H, et al (2024)

Inertial migration of polymer micelles in a square microchannel.

Soft matter [Epub ahead of print].

Using a hybrid simulation approach that combines a lattice-Boltzmann method for fluid flow and a molecular dynamics model for polymers, we investigate the inertial migration of star-like and crew-cut polymer micelles in a square microchannel. It is found that they exhibit two types of equilibrium positions, which shift further away from the center of the microchannel when the Reynolds number (Re) increases, as can be observed for soft particles. What differs from the behaviors of soft particles is that here, the blockage ratio is no longer the decisive factor. When the sizes are the same, the star-like micelles are always relatively closer to the microchannel wall as they gradually transition from spherical to disc-like with the increase of Re. In comparison, the crew-cut micelles are only transformed into an ellipsoid. Conversely, when the hydrophobic core sizes are the same, the equilibrium position of the star-like micelles becomes closer to that of the crew-cut micelles. Our results demonstrate that for polymer micelles with a core-shell structure, the equilibrium position is no longer solely determined by their overall dimensions but depends on the core and shell's specific dimensions, especially the hydrophobic core size. This finding opens up a new approach for achieving the separation of micelles in inertial migration.

RevDate: 2024-01-29

Maar K, Shavit U, Andersen A, et al (2024)

The fluid dynamics of barnacle feeding.

The Journal of experimental biology pii:342635 [Epub ahead of print].

Sessile barnacles feed by sweeping their basket-like cirral fan through the water, intercepting suspended prey. A primary component of the diet of adult barnacles is copepods that are sensitive to fluid disturbances and capable of escaping. How do barnacles manage to capture copepods despite the fluid disturbances they generate? We examined this question by describing the feeding current architecture of 1 cm sized Balanus crenatus using particle image velocimetry, and by studying the trajectories of captured copepods and the escapes of evading copepods. We find that barnacles produce a feeding current that arrives both from behind and the sides of the barnacle. The flow from the sides represents quiescent corridors of low fluid deformation and uninterrupted by the beating cirral fan. Potential prey arriving from behind are likely to encounter the cirral fan and, hence, capture here is highly unlikely. Accordingly, most captured copepods arrived through the quiet corridors, while most copepods arriving from behind managed to escape. Thus, it is the unique feeding flow architecture that allows feeding on evasive prey. We used the Landau-Squire jet as a simple model of the feeding current. For the Reynolds number of our experiments, the model reproduces the main features of the feeding current, including the lateral feeding corridors. Furthermore, the model suggests that smaller barnacle specimens, operating at lower Reynolds numbers, will produce a fore-and-aft symmetric feeding current without the lateral corridors. This suggests an ontogenetic diet shift from non-evasive prey to inclusion of evasive prey as the barnacle grows.

RevDate: 2024-01-29

Abbas N, Mustafa Z, Abodayeh K, et al (2023)

Darcy resistant of Soret and Dufour impact of radiative induced magnetic field sutterby fluid flow over stretching cylinder.

Heliyon, 9(12):e22503 pii:S2405-8440(23)09711-6.

The incompressible two-dimensional steady flow of Sutterby fluid over a stretching cylinder is taken into account. The magnetic Reynolds number is not deliberated low in the present analysis. Radiation and variable thermal conductivity are considered to debate the impact on the cylindrical surface. The Dufour and Soret impacts are considered on the cylinder. The mathematical model is settled by employing boundary layer approximations in the form of differential equations. The system of differential equations becomes dimensionless using suitable transformations. The dimensionless nonlinear differential equations are solved through a numerical scheme(bvp4c technique). The flow parameters of physical effects on the velocity, temperature, heat transfer rate, and friction between surface and liquid are presented in tabular as well as graphical form. The velocity function declined by improving the values of the Sponginess parameter. The fluid temperature is reduced by increment in curvature parameter.

RevDate: 2024-01-26

Chang L, Zhao G, Buren M, et al (2023)

Alternating Current Electroosmotic Flow of Maxwell Fluid in a Parallel Plate Microchannel with Sinusoidal Roughness.

Micromachines, 15(1): pii:mi15010004.

The EOF of a viscoelastic Maxwell fluid driven by an alternating pressure gradient and electric field in a parallel plate microchannel with sinusoidal roughness has been investigated within the Debye-Hückel approximation based on boundary perturbation expansion and separation of variables. Perturbation solutions were obtained for the potential distribution, the velocity and the mean velocity, and the relation between the mean velocity and the roughness. There are significant differences in the velocity amplitudes of the Newtonian and Maxwell fluids. It is shown here that the velocity distribution of the viscoelastic fluid is significantly affected by the roughness of the walls, which leads to the appearance of fluctuations in the fluid. Also, the velocity is strongly dependent on the phase difference θ of the roughness of the upper and lower plates. As the oscillation Reynolds number ReΩ increases, the velocity profile and the average velocity um(t) of AC EOF oscillate rapidly but the velocity amplitude decreases. The Deborah number De plays a similar role to ReΩ, which makes the AC EOF velocity profile more likely to oscillate. Meanwhile, phase lag χ (representing the phase difference between the electric field and the mean velocity) decreases when G and θ are increased. However, for larger λ (e.g., λ > 3), it almost has no phase lag χ.

RevDate: 2024-01-24

Salman M, Liu J, Chauhan R, et al (2024)

A MATLAB simulation-based analytical study of energy, exergy, and cost benefits in jet-impinged protrusion-roughened double pass solar air collector.

Environmental science and pollution research international [Epub ahead of print].

This study analyzes the performance and cost-effectiveness of a protrusion-roughened jet-impinged double-pass solar air collector (PRJDPSAC) within a Reynolds number (Re) range of 2500 to 22,500. Examining jet slot parameters, i.e., the jet height ratio (Hjp/Dhd = 0.11-0.44), stream-wise pitch ratio (Xjp/Dhd = 0.44-1.32), and span-wise pitch ratio (Yjp/Dhd = 0.44-1.32), the model demonstrates enhanced energy conversion, minimizes losses, improves efficiency, and brings positive economic impact, making it a promising solution for diverse applications including drying processes, livestock facilities, remote accommodations, and HVAC system pre-heating. The examination incorporates advanced MATLAB simulations to assess energy-exergy performance and cost viability. At lower Re values, both energy ([Formula: see text]) and exergy ([Formula: see text]) efficiencies increase uniformly; however, stabilization and decline occur at higher Re values. The maximum [Formula: see text] for the PRJDPSAC is 4.38% under a temperature rise parameter of 60 × 10[-3] Km[2]/W for obtaining optimum values of Xjp/Dhd = 1.32, Hjp/Dhd = 0.22, and Yjp/Dhd = 1.32, which is 31% higher than that of the smooth double-pass solar air collector (DPSAC). Economic benefits are significant for PRJDPSAC within mair (0.01-0.07 kg/s), but above 0.07 kg/s, the DPSAC becomes more cost-effective. Integrating simulation and experimental data, the study highlights MATLAB's effectiveness for solar energy system analysis and optimization, reinforcing the practicality of the proposed collector design.

RevDate: 2024-01-24

Wu Y, Wang F, Zheng S, et al (2024)

Evolution dynamics of thin liquid structures investigated using a phase-field model.

Soft matter [Epub ahead of print].

Liquid structures of thin-films and torus droplets are omnipresent in daily lives. The morphological evolution of liquid structures suspending in another immiscible fluid and sitting on a solid substrate is investigated by using three-dimensional (3D) phase-field (PF) simulations. Here, we address the evolution dynamics by scrutinizing the interplay of surface energy, kinetic energy, and viscous dissipation, which is characterized by Reynolds number Re and Weber number We. We observe special droplet breakup phenomena by varying Re and We. In addition, we gain the essential physical insights into controlling the droplet formation resulting from the morphological evolution of the liquid structures by characterizing the top and side profiles under different circumstances. We find that the shape evolution of the liquid structures is intimately related to the initial shape, Re, We as well as the intrinsic wettability of the substrate. Furthermore, it is revealed that the evolution dynamics are determined by the competition between the coalescence phenomenology and the hydrodynamic instability of the liquid structures. For the coalescence phenomenology, the liquid structure merges onto itself, while the hydrodynamic instability leads to the breakup of the liquid structure. Last but not least, we investigate the influence of wall relaxation on the breakup outcome of torus droplets on substrates with different contact angles. We shed light on how the key parameters including the initial shape, Re, We, wettability, and wall relaxation influence the droplet dynamics and droplet formation. These findings are anticipated to contribute insights into droplet-based systems, potentially impacting areas like ink-jet printing, drug delivery systems, and microfluidic devices, where the interplay of surface energy, kinetic energy, and viscous dissipation plays a crucial role.

RevDate: 2024-01-24

Jeon H, Lee SH, Shin J, et al (2024)

Elasto-inertial microfluidic separation of microspheres with submicron resolution at high-throughput.

Microsystems & nanoengineering, 10:15.

Elasto-inertial microfluidic separation offers many advantages including high throughput and separation resolution. Even though the separation efficiency highly depends on precise control of the flow conditions, no concrete guidelines have been reported yet in elasto-inertial microfluidics. Here, we propose a dimensionless analysis for precise estimation of the microsphere behaviors across the interface of Newtonian and viscoelastic fluids. Reynolds number, modified Weissenberg number, and modified elastic number are used to investigate the balance between inertial and elastic lift forces. Based on the findings, we introduce a new dimensionless number defined as the width of the Newtonian fluid stream divided by microsphere diameter. The proposed dimensionless analysis allows us to predict whether the microspheres migrate across the co-flow interface. The theoretical estimation is found to be in good agreement with the experimental results using 2.1- and 3.2-μm-diameter polystyrene microspheres in a co-flow of water and polyethylene oxide solution. Based on the theoretical estimation, we also realize submicron separation of the microspheres with 2.1 and 2.5 μm in diameter at high throughput, high purity (>95%), and high recovery rate (>97%). The applicability of the proposed method was validated by separation of platelets from similar-sized Escherichia coli (E.coli).

RevDate: 2024-01-22

Macías MM, García-Ortiz JH, Oliveira TF, et al (2024)

Numerical Investigation of Dimensionless Parameters in Carangiform Fish Swimming Hydrodynamics.

Biomimetics (Basel, Switzerland), 9(1): pii:biomimetics9010045.

Research into how fish and other aquatic organisms propel themselves offers valuable natural references for enhancing technology related to underwater devices like vehicles, propellers, and biomimetic robotics. Additionally, such research provides insights into fish evolution and ecological dynamics. This work carried out a numerical investigation of the most relevant dimensionless parameters in a fish swimming environment (Reynolds Re, Strouhal St, and Slip numbers) to provide valuable knowledge in terms of biomechanics behavior. Thus, a three-dimensional numerical study of the fish-like lambari, a BCF swimmer with carangiform kinematics, was conducted using the URANS approach with the k-ω-SST transition turbulence closure model in the OpenFOAM software. In this study, we initially reported the equilibrium Strouhal number, which is represented by St∗, and its dependence on the Reynolds number, denoted as Re. This was performed following a power-law relationship of St∝Re(-α). We also conducted a comprehensive analysis of the hydrodynamic forces and the effect of body undulation in fish on the production of swimming drag and thrust. Additionally, we computed propulsive and quasi-propulsive efficiencies, as well as examined the influence of the Reynolds number and Slip number on fish performance. Finally, we performed a vortex dynamics analysis, in which different wake configurations were revealed under variations of the dimensionless parameters St, Re, and Slip. Furthermore, we explored the relationship between the generation of a leading-edge vortex via the caudal fin and the peak thrust production within the motion cycle.

RevDate: 2024-01-20

Xiong J, Liu X, Feng H, et al (2023)

Inertial migration of spherical and oblate particles in a triangular microchannel.

Physical review. E, 108(6-2):065105.

The. inertial migration of both spherical and oblate particles within an equilateral triangular channel is studied numerically. Our study primarily focuses on the effects of fluid inertia, quantified by the Reynolds number (Re) and particle size (β). Our observations reveal two distinct equilibrium positions: the corner equilibrium position (CEP) is situated along the angle bisector near the corner, while the face equilibrium position (FEP) is located on a segment of the line perpendicular from the triangle's center to one of its sides. Spherical particles with varying initial positions predominantly reach the FEP. For oblate particles initially positioned along the angle bisector with a specific orientation, meaning the particle's evolution axis is inside the plane bisecting the angle, they will migrate along the angle bisector to reach the CEP while rotating in the tumbling mode. Conversely, for particles with different initial orientations and positions, they will employ the log-rolling mode to reach the FEP. Notably, we identify a dual-stage particle migration process to the FEP, with trajectories converging to an equilibrium manifold, which bears a resemblance to the cross section of the channel. To further illustrate the transition between FEP and CEP under general initial conditions, except for those along the angle bisector, we construct a phase diagram in the (Re, β) parameter space. This transition is often triggered by the size of larger particles (as the FEP cannot accommodate them) or the influence of inertia for smaller particles. For the FEP, especially for medium- or small-size particles, we notice an initial outward movement of the FEP from the center of the cross section as Re increases, followed by a return towards the center. This behavior results from the interplay of three forces acting on the particle. This research holds potential implications for the design of microfluidic devices, offering insights into the behavior of particles within equilateral triangular channels.

RevDate: 2024-01-20

Wang S, Wang J, J Deng (2023)

Effect of layer thickness for the bounce of a particle settling through a density transition layer.

Physical review. E, 108(6-2):065108.

We study numerically a spherical particle settling through a density transition layer at moderate Reynolds numbers Re_{u}=69∼259 for the upper fluid. We investigate how the transition layer thickness affects the particle's bouncing behavior as it crosses the interface. The previous intuitive understanding was that the bounce occurs when the relative thickness of the transition layer, L/D, which is characterized by the ratio of the layer thickness L to the particle diameter D, is small. Indeed, we report no bounce phenomenon for very thick interfaces, i.e., L/D>10 in the current parametric range. However, we argue that the bounce can also be inhibited when L/D is too small. Upon a fixed upper layer Reynolds number Re_{u}=207 with varying L/D, we examine the flow evolution of these cases. We propose that this inhibition is attributed to two mechanisms. First, as the interface thickness decreases, the detachment of the attached lighter fluid from the upper layer occurs more rapidly, resulting in a faster decrease in buoyancy. Second, in the case of a very thin interface (L/D=0.5-3.0), the residual light fluid accumulates and undergoes a secondary detachment, separating from the particle at an angle relative to the central axis. This secondary detachment reduces the drag force and effectively prevents the particle from experiencing a rebound motion.

RevDate: 2024-01-18

Liu T, Deng H, He F, et al (2024)

Synthesizing high performance LNMO cathode materials with porous structure by manipulating Reynolds number in a microreactor.

Nanotechnology [Epub ahead of print].

The demand for Lithium-ion batteries (LIBs) has significantly grown in the last decade due to their extensive use electric vehicles (EVs). To further advance the commercialization of LIBs for various applications, there is a pressing need to develop electrode materials with enhanced performance. The porous microsphere morphology LiNixMn2-xO4 (LNMO) is considered to be an effective material with both high energy density and excellent rate performance. Nevertheless, LNMO synthesis technology still has problem such as long reaction time, high energy consumption and environmental pollution. Herein, LNMO microsphere was successfully synthesized with short precursors reaction time (18 seconds) at 40oC without using chelating agent by microreaction technology combined solid-state lithiation. The optimized LNMO cathode shows microsphere (~8μm) morphology stacked by nano primary particles, with abundant mesoporous and fully exposed low-energy plane. The electrochemical analysis indicates that the optimized LNMO cathode demonstrates 97.33% capacity retention even after 200 cycles at 1C. Additionally, the material shows a highly satisfactory discharge capacity of 92.3 mAh·g-1 at 10C. Overall, microreaction technology is anticipated to offer a novel approach in the synthesis of LNMO cathode materials with excellent performance.

RevDate: 2024-01-17

Ashraf H, Siddique I, Siddiqa A, et al (2024)

Analysis of two layered peristaltic-ciliary transport of Jeffrey fluid and in vitro preimplantation embryo development.

Scientific reports, 14(1):1469.

The analysis of peristaltic-ciliary transport in the human female fallopian tube, specifically in relation to the growing embryo, is a matter of considerable physiological importance. This paper proposes a biomechanical model that incorporates a finite permeable tube consisting of two layers, where the Jeffrey fluid model characterizes the viscoelastic properties of the growing embryo and continuously secreting fluid. Jeffrey fluid entering with some negative pressure gradient forms the core fluid layer while continuously secreting Jeffrey fluid forms the peripheral fluid layer. The resulting partial differential equations are solved for closed-form solutions after employing the assumption of long wavelength. The analysis delineated that increasing the constant secretion velocity, Darcy number, and Reynolds number leads to a decrease in the appropriate residue time of the core fluid layer and a reduction in the size of the secreting fluid bolus in the peripheral fluid layer. Eventually, the boluses completely disappear when the constant secretion velocity exceeds 3.0 Progesterone ([Formula: see text]) and estradiol ([Formula: see text]) directly regulate the transportation of the growing embryo, while luteinizing hormone (LH) and follicle-stimulating hormone (FSH), prolactin, anti-mullerian hormone (AMH), and thyroid-stimulating hormone (TSH) have an indirect effects. Based on the number and size of blastomeres, the percentage of fragmentation, and the presence of multinucleated blastomeres two groups were formed in an in vitro experiment. Out of 50 patients, 26 (76.5%) were pregnant in a group of the good quality embryos, and only 8 (23.5%) were in a group of the bad quality embryos. The transport of growing embryo in the human fallopian tube and preimplantation development of human embryos in in vitro are constraint by baseline hormones FSH, LH, prolactin, [Formula: see text], AMH, and TSH.

RevDate: 2024-01-17

Akbar NS, Rafiq M, Muhammad T, et al (2024)

Microbic flow analysis of nano fluid with chemical reaction in microchannel with flexural walls under the effects of thermophoretic diffusion.

Scientific reports, 14(1):1474.

The current investigation examines the peristaltic flow, in curved conduit, having complaint boundaries for nanofluid. The effects of curvature are taken into account when developing the governing equations for the nano fluid model for curved channels. Nonlinear & coupled differential equations are then simplified by incorporating the long wavelength assumption along with smaller Reynolds number. The homotopy perturbation approach is used to analytically solve the reduced coupled differential equations. The entropy generation can be estimated through examining the contributions of heat and fluid viscosities. The results of velocity, temperature, concentration, entropy number, and stream functions have been plotted graphically in order to discuss the physical attributes of the essential quantities. Increase in fluid velocity within the curved conduit is noticed for higher values of thermophoresis parameter and Brownian motion parameter further entropy generation number is boosted by increasing values of Grashof number.

RevDate: 2024-01-12

Allehiany FM, Riaz A, Shoukat S, et al (2023)

Three dimensional study for entropy optimization in nanofluid flow through a compliant curved duct: A drug delivery and therapy application.

Heliyon, 9(12):e22255.

This research explores the three-dimensional characteristics of nanofluid dynamics within curved ducts, in contrast to earlier studies that mainly focus on two-dimensional flow. By using this ground-breaking method, we can capture a more accurate depiction of fluid behavior that complies with the intricate duct design. In this study, we investigate the three dimensional flow and entropic analysis of peristaltic nanofluid flows in a flexible curved duct, comparing the effects of silver and copper nanoparticles. To obtain accurate results, we assume physical constraints such as long wavelength and low Reynolds number and used a perturbation technique through NDSolve commands for finding exact solutions of the obtained differential equations. A comprehensive error analysis is provided through residual error table and figures to estimate a suitable range of the physical factors. Our findings indicate that the velocity of the nanofluid is directly proportional to the elasticity of the walls, while the mass per unit volume inversely affects velocity. We show that reducing the aspect ratio of the duct rectangular section can decrease entropy generation by raising magnitudes of damping force exerted by to the flexible walls of the enclosure. Additionally, using a larger height of the channel than the breadth can reduce stream boluses. The practical implications of this study extend beyond turbines and endoscopy to biomedical processes such as drug delivery and microfluidic systems.

RevDate: 2024-01-11

Uttieri M, L Svetlichny (2024)

Escape performance in the cyclopoid copepod Oithona davisae.

Scientific reports, 14(1):1078.

Escaping a predator is one of the keys to success for any living creature. The performance of adults (males, females, and ovigerous females) of the cyclopoid copepod Oithona davisae exposed to an electrical stimulus is analysed as a function of temperature by measuring characteristic parameters associated with the escape movement (distance covered, duration of the appendage movement, mean and maximum escape speeds, Reynolds number). In addition, as a proxy for the efficiency of the motion, the Strouhal number was calculated. The escape performance showed temperature-dependent relationships within each adult state, as well as differences between sexes; additionally, changes owing to the presence of the egg sac were recorded in females. In a broader perspective, the results collected reveal the occurrence of different behavioural adaptations in males and females, adding to the comprehension of the mechanisms by which O. davisae interacts with its environment and shedding new light on the in situ population dynamics of this species.

RevDate: 2024-01-10

Banerjee A, Pavithran I, RI Sujith (2024)

Early warnings of tipping in a non-autonomous turbulent reactive flow system: Efficacy, reliability, and warning times.

Chaos (Woodbury, N.Y.), 34(1):.

Real-world complex systems such as the earth's climate, ecosystems, stock markets, and combustion engines are prone to dynamical transitions from one state to another, with catastrophic consequences. State variables of such systems often exhibit aperiodic fluctuations, either chaotic or stochastic in nature. Often, the parameters describing a system vary with time, showing time dependency. Constrained by these effects, it becomes difficult to be warned of an impending critical transition, as such effects contaminate the precursory signals of the transition. Therefore, a need for efficient and reliable early-warning signals (EWSs) in such complex systems is in pressing demand. Motivated by this fact, in the present work, we analyze various EWSs in the context of a non-autonomous turbulent thermoacoustic system. In particular, we investigate the efficacy of different EWS in forecasting the onset of thermoacoustic instability (TAI) and their reliability with respect to the rate of change of the control parameter. This is the first experimental study of tipping points in a non-autonomous turbulent thermoacoustic system. We consider the Reynolds number (Re) as the control parameter, which is varied linearly with time at finite rates. The considered EWSs are derived from critical slowing down, spectral properties, and fractal characteristics of the system variables. The state of TAI is associated with large amplitude acoustic pressure oscillations that could lead thermoacoustic systems to break down. We consider acoustic pressure fluctuations as a potential system variable to perform the analysis. Our analysis shows that irrespective of the rate of variation of the control parameter, the Hurst exponent and variance of autocorrelation coefficients warn of an impending transition well in advance and are more reliable than other EWS measures. Additionally, we show the variation in the warning time to an impending TAI with rates of change of the control parameter. We also investigate the variation in amplitudes of the most significant modes of acoustic pressure oscillations with the Hurst exponent. Such variations lead to scaling laws that could be significant in prediction and devising control actions to mitigate TAI.

RevDate: 2024-01-09

Faisal S, Barbour M, Seibel EJ, et al (2024)

Hemodynamics of Saline Flushing in Endoscopic Imaging of Partially Occluded Coronary Arteries.

Cardiovascular engineering and technology [Epub ahead of print].

PURPOSE: Intravascular endoscopy can aid in the diagnosis of coronary atherosclerosis by providing direct color images of coronary plaques. The procedure requires a blood-free optical path between the catheter and plaque, and achieving clearance safely remains an engineering challenge. In this study, we investigate the hemodynamics of saline flushing in partially occluded coronary arteries to advance the development of intravascular forward-imaging catheters that do not require balloon occlusion.

METHODS: In-vitro experiments and CFD simulations are used to quantify the influence of plaque size, catheter stand-off distance, saline injection flowrate, and injection orientation on the time required to achieve blood clearance.

RESULTS: Experiments and simulation of saline injection from a dual-lumen catheter demonstrated that flushing times increase both as injection flow rate (Reynolds number) decreases and as the catheter moves distally away from the plaque. CFD simulations demonstrated that successful flushing was achieved regardless of lumen axial orientation in a 95% occluded artery. Flushing time was also found to increase as plaque size decreases for a set injection flowrate, and a lower limit for injection flowrate was found to exist for each plaques size, below which clearance was not achieved. For the three occlusion sizes investigated (90, 95, 97% by area), successful occlusion was achieved in less than 1.2 s. Investigation of the pressure fields developed during injection, highlight that rapid clearance can be achieved while keeping the arterial overpressure to < 1 mmHg.

CONCLUSIONS: A dual lumen saline injection catheter was shown to produce clearance safely and effectively in models of partially occluded coronary arteries. Clearance was achieved across a range of engineering and clinical parameters without the use of a balloon occlusion, providing development guideposts for a fluid injection system in forward-imaging coronary endoscopes.

RevDate: 2024-01-05

Inubushi M, Saiki Y, Kobayashi MU, et al (2023)

Characterizing Small-Scale Dynamics of Navier-Stokes Turbulence with Transverse Lyapunov Exponents: A Data Assimilation Approach.

Physical review letters, 131(25):254001.

Data assimilation (DA) of turbulence, which involves reconstructing small-scale turbulent structures based on observational data from large-scale ones, is crucial not only for practical forecasting but also for gaining a deeper understanding of turbulent dynamics. We propose a theoretical framework for DA of turbulence based on the transverse Lyapunov exponents (TLEs) in synchronization theory. Through stability analysis using TLEs, we identify a critical length scale as a key condition for DA; turbulent dynamics smaller than this scale are synchronized with larger-scale turbulent dynamics. Furthermore, considering recent findings for the maximal Lyapunov exponent and its relation with the TLEs, we clarify the Reynolds number dependence of the critical length scale.

RevDate: 2024-01-04

Akbar NS, Rafiq M, Muhammad T, et al (2024)

Electro osmotically interactive biological study of thermally stratified micropolar nanofluid flow for Copper and Silver nanoparticles in a microchannel.

Scientific reports, 14(1):518.

A novel mathematical analysis is established that summits the key features of peristaltic propulsion for a non-Newtonian micropolar fluid with the electroosmosis and heat transfer enhancement using nanoparticles. In such physiological models, the channel have a symmetric configuration in accordance with the biological problem. Being mindful of this fact, we have disclosed an integrated analysis on symmetric channel that incorporates major physiological applications. The creeping flow inference is reviewed to model this realistic problem. Flow equations are model using cartesian coordinates and simplified using long wave length and low Reynolds number approximation. Nonlinear linear couple equations are solving numerically. We have studied the variation in the properties of nanofluid developed by two different types of nanoparticles (i.e. Cu and Ag nanoparticles). Graphical illustrations are unveiled to highlight the physical aspects of nanoparticles and flow parameters. The exploration demonstrates that the micro-rotation of the nano-liquid elements enhances the thermal conductivity of the fluid movement. The effect of micropolar fluid parameters on mean flow and pressure variables is also presented.

RevDate: 2024-01-04

Chinnasamy P, Sivajothi R, Sathish S, et al (2024)

Peristaltic transport of Sutterby nanofluid flow in an inclined tapered channel with an artificial neural network model and biomedical engineering application.

Scientific reports, 14(1):555.

Modern energy systems are finding new applications for magnetohydrodynamic rheological bio-inspired pumping systems. The incorporation of the electrically conductive qualities of flowing liquids into the biological geometries, rheological behavior, and propulsion processes of these systems was a significant effort. Additional enhancements to transport properties are possible with the use of nanofluids. Due to their several applications in physiology and industry, including urine dynamics, chyme migration in the gastrointestinal system, and the hemodynamics of tiny blood arteries. Peristaltic processes also move spermatozoa in the human reproductive system and embryos in the uterus. The present research examines heat transport in a two-dimensional deformable channel containing magnetic viscoelastic nanofluids by considering all of these factors concurrently, which is vulnerable to peristaltic waves and hall current under ion slip and other situations. Nanofluid rheology makes use of the Sutterby fluid model, while nanoscale effects are modeled using the Buongiorno model. The current study introduces an innovative numerical computing solver utilizing a Multilayer Perceptron feed-forward back-propagation artificial neural network (ANN) with the Levenberg-Marquardt algorithm. Data were collected for testing, certifying, and training the ANN model. In order to make the dimensional PDEs dimensionless, the non-similar variables are employed and calculated by the Homotopy perturbation technique. The effects of developing parameters such as Sutterby fluid parameter, Froude number, thermophoresis, ion-slip parameter, Brownian motion, radiation, Eckert number, and Hall parameter on velocity, temperature, and concentration are demonstrated. The machine learning model chooses data, builds and trains a network, and subsequently assesses its performance using the mean square error metric. Current results declare that the improving Reynolds number tends to increase the pressure rise. Improving the Hall parameter is shown to result in a decrease in velocity. When raising a fluid's parameter, the temperature profile rises.

RevDate: 2024-01-03

Heronimczak M, Mrowiec A, Rząsa M, et al (2024)

Measurements of the flow of a liquid-solid mixture/suspension through a segmented orifice.

Scientific reports, 14(1):269.

The paper attempts to solve the metrological problem that occurs when measuring the intensity of a flowing fluid with suspended solids with densities greater and less than the density of the fluid. The issue of the possibility of self-cleaning of a prototype variant of a segmented orifice from floating solid particles forming mixture/suspensions is discussed. For spherical particles of solids calculations have been made to allow for determining a borderline between their floating and entrainment by the flow, based on dimensionless numbers: Archimedes number and Reynolds number. Experimental tests and CFD simulations were conducted with a variable flow determined by Reynolds number for comparable segmental orifices with orifice module m = 0.102. Flow characteristics were plotted. Based on the results obtained from numerical simulations, positive influence of the inclination of skew segmental orifice downflow plane was presented. The results obtained from the study are a guideline for planning further studies to expand the knowledge of segmented orifices with inclined inflow plane.

RevDate: 2024-01-02

Jubaer H, Thomas M, Farkas D, et al (2024)

Development of an effective two-equation turbulence modeling approach for simulating aerosol deposition across a range of turbulence levels.

Journal of aerosol science, 175:106262.

Pharmaceutical aerosol systems present a significant challenge to computational fluid dynamics (CFD) modeling based on the need to capture multiple levels of turbulence, frequent transition between laminar and turbulent flows, anisotropic turbulent particle dispersion, and near-wall particle transport phenomena often within geometrically complex systems over multiple time scales. Two-equation turbulence models, such as the k-ω family of approximations, offer a computationally efficient solution approach, but are known to require the use of near-wall (NW) corrections and eddy interaction model (EIM) modifications for accurate predictions of aerosol deposition. The objective of this study was to develop an efficient and effective two-equation turbulence modeling approach that enables accurate predictions of pharmaceutical aerosol deposition across a range of turbulence levels. Key systems considered were the traditional aerosol deposition benchmark cases of a 90-degree bend (Re=6,000) and a vertical straight section of pipe (Re=10,000), as well as a highly complex case of direct-to-infant (D2I) nose-to-lung pharmaceutical aerosol delivery from an air-jet dry powder inhaler (DPI) including a patient interface and infant nasal geometry through mid-trachea (500

RevDate: 2023-12-28

Xu Z, Chen Z, Yang S, et al (2023)

Passive Focusing of Single Cells Using Microwell Arrays for High-Accuracy Image-Activated Sorting.

Analytical chemistry [Epub ahead of print].

Sorting single cells from a population was of critical importance in areas such as cell line development and cell therapy. Image-based sorting is becoming a promising technique for the nonlabeling isolation of cells due to the capability of providing the details of cell morphology. This study reported the focusing of cells using microwell arrays and the following automatic size sorting based on the real-time recognition of cells. The simulation first demonstrated the converged streamlines to the symmetrical plane contributed to the focusing effect. Then, the influence of connecting microchannel, flowing length, particle size, and the sample flow rate on the focusing effect was experimentally analyzed. Both microspheres and cells could be aligned in a straight line at the Reynolds number (Re) of 0.027-0.187 and 0.027-0.08, respectively. The connecting channel was proved to drastically improve the focusing performance. Afterward, a tapered microwell array was utilized to focus sphere/cell spreading in a wide channel to a straight line. Finally, a custom algorithm was employed to identify and sort the size of microspheres/K562 cells with a throughput of 1 event/s and an accuracy of 97.8/97.1%. The proposed technique aligned cells to a straight line at low Reynolds numbers and greatly facilitated the image-activated sorting without the need for a high-speed camera or flow control components with high frequency. Therefore, it is of enormous application potential in the field of nonlabeled separation of single cells.

RevDate: 2023-12-27

Shams M, S Sarwar (2023)

Channelized water driven flow of MHD carbon-nanotube nanofluid influenced by rotation, heat source and thermal radiation.

PloS one, 18(12):e0295406 pii:PONE-D-22-34242.

The efficiency enhancements of thermal energy systems are made with advancements made in the effective use of thermal solar collectors, operating fluid and the introduction of curved and transparent solar panels. In this paper, we present a prototype theoretical/mathematical model for the carbon nanotube-based curved solar panels combined with the solar thermal collector and the porous rotating channel. The analysis is carried out to study the effect of transversely applied magnetic, rotation of the porous channel, linear thermal radiation and the uniformly distributed heat source on the heat transfer characteristics of the single-walled (SWCNT) and multi-walled carbon nanotubes (MWCNT). Due to the nonlinearity of the governing momentum and the heat transport equations and the limitation of the exact methods, numerical similarity solutions are obtained for the boundary value problem using the MATLAB function bvp4c. Influences of different parameters are observed through graphs on the nanofluid flow and temperature profiles. The velocity profile exhibits dual behavior for rising the nanoparticles' volume fraction, the magnetic parameter, rotation, and the Reynolds number. The temperature profile increases with increasing nanoparticles and heat source parameters and decreases for increasing suction, rotation, Reynolds number, and thermal radiation. In some cases, flow profiles for SWCNT exceed those of MWCNT.

RevDate: 2023-12-27

Jahangiri AR, Ziarati N, Dadkhah E, et al (2023)

Microfluidics: The future of sperm selection in assisted reproduction.

Andrology [Epub ahead of print].

BACKGROUND: Obtaining functional sperm cells is the first step to treat infertility. With the ever-increasing trend in male infertility, clinicians require access to effective solutions that are able to single out the most viable spermatozoa, which would max out the chance for a successful pregnancy. The new generation techniques for sperm selection involve microfluidics, which offers laminar flow and low Reynolds number within the platforms can provide unprecedented opportunities for sperm selection. Previous studies showed that microfluidic platforms can provide a novel approach to this challenge and since then researchers across the globe have attacked this problem from multiple angles.

OBJECTIVE: In this review, we seek to provide a much-needed bridge between the technical and medical aspects of microfluidic sperm selection. Here, we provide an up-to-date list on microfluidic sperm selection procedures and its application in assisted reproductive technology laboratories.

SEARCH METHOD: A literature search was performed in Web of Science, PubMed, and Scopus to select papers reporting microfluidic sperm selection using the keywords: microfluidic sperm selection, self-motility, non-motile sperm selection, boundary following, rheotaxis, chemotaxis, and thermotaxis. Papers published before March 31, 2023 were selected.

OUTCOMES: Our results show that most studies have used motility-based properties for sperm selection. However, microfluidic platforms are ripe for making use of other properties such as chemotaxis and especially rheotaxis. We have identified that low throughput is one of the major hurdles to current microfluidic sperm selection chips, which can be solved via parallelization.

CONCLUSION: Future work needs to be performed on numerical simulation of the microfluidics chip prior to fabrication as well as relevant clinical assessment after the selection procedure. This would require a close collaboration and understanding among engineers, biologists, and medical professionals. It is interesting that in spite of two decades of microfluidics sperm selection, numerical simulation and clinical studies are lagging behind. It is expected that microfluidic sperm selection platforms will play a major role in the development of fully integrated start-to-finish assisted reproductive technology systems.

RevDate: 2023-12-25

Liu L, Meng Z, Zhang Y, et al (2023)

Simulation of High-Viscosity Generalized Newtonian Fluid Flows in the Mixing Section of a Screw Extruder Using the Lattice Boltzmann Model.

ACS omega, 8(50):47991-48018.

The mixing quality of polymer melts in the mixing section of a single-screw extruder and an injection molding machine has considerable effects on the properties of the molded products. Therefore, the study of the flow field of polymer melts in the mixing section is of great importance. The lattice Boltzmann method (LBM) exhibits unique advantages in simulating non-Newtonian fluids. Many researchers have used LBM to study the flow of medium- and low-viscosity fluids. In their studies, the Reynolds number of fluid flows is generally moderate. However, polymer melts are typical high-viscosity fluids, and their flow Reynolds number is generally very small. The single-relaxation-time lattice Boltzmann method (SRT-LBM) has been used previously to study the flow field of power law fluids in the mixing section. Herein, the flow field of high-viscosity generalized Newtonian fluids in the mixing section of a single-screw extruder is studied using SRT-LBM, the two-relaxation-time lattice Boltzmann method (TRT-LBM), and the multiple-relaxation-time lattice Boltzmann method (MRT-LBM). Through comparison, TRT-LBM has been found to exhibit obvious advantages regarding stability, calculation accuracy, calculation efficiency, and selection of simulation parameters. The TRT-LBM is more suitable for studying high-viscosity generalized Newtonian fluids than SRT-LBM and MRT-LBM. SRT-LBM has low computational efficiency when simulating high-viscosity generalized Newtonian fluids, and instability is easily caused when the fluid has a yield stress. For MRT-LBM, only by studying the relaxation parameters can its advantages be fully utilized. However, optimizing the accuracy and stability of the MRT-LBM via parameter research and linear stability analysis is difficult. For non-Newtonian fluids, it is difficult to optimize the relaxation parameters to make the MRT-LBM more stable and accurate than the TRT-LBM. It is difficult for the MRT-LBM to realize its potential when simulating high-viscosity generalized Newtonian fluids. In addition, we studied the flow pattern in the cross section of the screw channel and compared it to the results reported in previous studies.

RevDate: 2023-12-22

Qiao Z, Pan Y, Tang Y, et al (2023)

Numerical Simulation of Membrane Separation Characteristics of Supercritical Carbon Dioxide and Water.

Membranes, 13(12): pii:membranes13120892.

To solve the problem of water carryover in the supercritical CO2 separation and mining process in the CO2 plume geothermal system, a three-dimensional shell-tube hollow fiber membrane absorption separator is designed in this study. A coupled species transport model, a porous medium model, and an absorption mathematical model are established, and the flow field and separation characteristics in the circular and flat tubes are analyzed using numerical simulation. The results show that the membrane separation efficiency increases with an increase in the flatness and membrane tube length. When the inlet velocity of the mixture is 0.1 m/s, the separation efficiency can reach 75.92%. Selecting a smaller flow Reynolds number and a more significant membrane tube flatness will reduce the water mass fraction at the outlet. When adding baffles of different shapes to the membrane tube, the mixture fluid in the membrane tube meanders forward and flows in the shape of "Z" under the blocking effect of the arcuate baffles. With an increase in the number of arcuate baffles in the membrane tube, the membrane separation efficiency of the separator increases continuously. The mixture fluid flows in the membrane tube with the built-in torsional baffles in a spiral manner, and the separation efficiency of the membrane separator increases with a torsion ratio reduction in the membrane tube.

RevDate: 2023-12-20

L'Estimé M, Schindler M, Shahidzadeh N, et al (2023)

Droplet Size Distribution in Emulsions.

Langmuir : the ACS journal of surfaces and colloids [Epub ahead of print].

The droplet size in emulsions is known to affect the rheological properties and plays a crucial role in many applications of emulsions. Despite its importance, the underlying mechanisms governing droplet size in emulsification remain poorly understood. We investigate the average drop size and size distribution upon emulsification with a high-shear mixer for model oil-in-water emulsions stabilized by a surfactant. The size distribution is found to be a log-normal distribution resulting from the repetitive random breakup of drops. High-shear emulsification, the usual way of making emulsions, is therefore found to be very different from turbulent emulsification given by the Kolmogorov-Hinze theory, for which power-law distributions of the drop size are expected. In agreement with this, the mean droplet size does not follow a scaling with the Reynolds number of the emulsification flow but rather a capillary number scaling based on the viscosity of the continuous phase.

RevDate: 2023-12-20

Tang Y, Li G, Wu J, et al (2023)

Charging characteristics of long distance accumulator for underwater electro-hydraulic control system.

The Review of scientific instruments, 94(12):.

Long distance accumulators are widely used in underwater electro-hydraulic control systems. However, as the working depth increases, the underwater umbilical cable becomes longer. The actual physical properties of the gas in the accumulator change. These factors affect the charging characteristics of the accumulator. To address the above issues, a simulation model of the charging of the long distance accumulator under real operating conditions is developed. Among them, the real properties of the gas inside the accumulator were calculated using the Redlich-Kwong-Soave method. The coefficient of friction within the umbilical cable is based on the Reynolds number and relative roughness. The simulation data were compared with the experimental results in the South China Sea to verify the accuracy of the simulation model. The effects of key factors on the charging characteristics of the long distance accumulators were also analyzed. The results show that the simulation results are in good agreement with the experimental results. The law of accumulator charging was analyzed: the greater the pressure of the gas source, the smaller the accumulator charging time; the greater the working water depth, the shorter the accumulator charging time. The research provides guidance for the design of long distance accumulators.

RevDate: 2023-12-14

Bao H, Song B, Ma D, et al (2023)

Aerodynamic performance of flapping wing with alula under different kinematics of complex flapping motion.

Bioinspiration & biomimetics, 19(1):.

The flight of birds is a remarkable feat, and their remarkable ability to fly derives from complex multi-degree-of-freedom flapping motions and small-scale feather structures that have evolved over millions of years. One of these feather structures is the alula, which can enhance the birds' flight performance at low speeds and large angles of attack. Previous studies on the alula have focused on the steady state. This undoubtedly ignores the unsteady effect caused by complex flapping motion, which is also the most important characteristic of avian flight. Therefore, this paper carries out a study on the effect of different motion modes and motion parameters on the aerodynamic mechanism of the alula. Previous studies found the dominate effect in the lift enhancement is influenced by Reynolds number, stall condition and geometric parameters. After coupling complex flapping motion, aerodynamic characteristics of the flapping wing are greatly influenced by different motion patterns and parameters. For pure plunge motion, both the slot effect and the vortex generator effect of the alula dominate the lift enhancement; while for plunge-twist and plunge-sweep motion, the vortex generator dominates more. At a low plunge amplitude, a low twist amplitude and a low sweep amplitude, the deflection of the alula has a good lift enhancement compared with the baseline wing. Increasing these amplitudes attenuates both the slot effect and the vortex generator effect. The alula can enhance the lift by 10.4% at the plunge amplitude of 25 deg (for pure plunge motion), by 7.9% at the plunge amplitude of 25 deg and twist amplitude of 10 deg (for plunge-twist motion), by 3.3% at the plunge amplitude of 25 deg and sweep amplitude of 15 deg (for plunge-sweep motion). Meanwhile, at a large sweep phase angle, the alula has a better lift enhancement. Increasing the phase angle enhances the vortex generator effect of the alula, and it has an optimal lift enhancement effect of 11% at the phase angle of 180 deg.

RevDate: 2023-12-13

Shuvo MS, Mahmud MJ, S Saha (2023)

Multi-scaling analysis of turbulent boundary layers over an isothermally heated flat plate with zero pressure gradient.

Heliyon, 9(12):e22721 pii:S2405-8440(23)09929-2.

A meticulous investigation into turbulent boundary layers over an isothermally heated flat plate with zero pressure gradient has been conducted. Eight distinct turbulence models, including algebraic yPlus, standard k-ω, standard k-ε, length-velocity, Spalart-Allmaras, low Reynolds number k-ε, shear stress transport, and v[2]-f turbulence models, are carefully chosen for numerical simulation alongside thermal energy and Reynolds-Averaged Navier-Stokes equations. A comparative analysis has determined that the Spalart-Allmaras model exhibits remarkable agreement with the results from direct numerical simulation, making it a reliable tool for predicting turbulent heat transfer and fluid flow, particularly at higher Prandtl and Reynolds numbers. Subsequently, a multi-scale investigation employs a comprehensive four-layer structure scheme and encompasses various momentum thickness Reynolds numbers of 1432, 2522, and 4000, and Prandtl numbers of 0.71, 2, and 5. The subsequent investigation reveals the governing non-dimensional numbers' substantial impact on the distribution and magnitude of mean thermal and flow characteristics. Notably, the scaling of mean thermal and momentum fields discloses the existence of a meso or intermediate layer characterized by a logarithmic nature unique to itself. The multi-scaling analysis of the flow field demonstrates greater conformity with the selected scaling variables primarily relying on the Reynolds number. Furthermore, the scaling of the energy field yields compelling outcomes within the inner and intermediate layers. However, according to the four-layer theory, minor discrepancies are observed in the outer layer when using the current scaling.

RevDate: 2023-12-12

Akram MM, Nazila Hosseini S, Levesque J, et al (2023)

A fully-flexible and thermally adjustable implantable neural probe with a U-turn polyester microchannel.

Annual International Conference of the IEEE Engineering in Medicine and Biology Society. IEEE Engineering in Medicine and Biology Society. Annual International Conference, 2023:1-4.

This work presents a fully flexible implantable neural probe fabricated with Polydimethylsiloxane (PDMS) and including a thermally-tunable stiffness microchannel filled with Polyester. The probe includes an optimized microfluidics mixer for drug delivery. Polyester, which is solid at room temperature and has a low melting point close to body temperature, is used to decrease the stiffness of the probe after insertion, after getting in contact with tissues. We designed a U-turn microchannel inside the PDMS neural probe and filled it up with melted polyester. The microchannel has a cross-section of 30 μm × 5 μm and a length of 14.7 mm. The following probe dimensions were chosen after extensive simulation: thickness = 20 μm, width = 300 μm, and length = 7 mm. These values yield a buckling force above 1 mN, which is sufficient for proper insertion into the brain tissues. Simulation results show that the microfluidics mixer with a cross-section of 90 μm × 5 μm and a length of 7 mm has optimum performance for the desired flow rate and quantity of drug to deliver. The pressure drop inside the microfluidic channel is less than 0.43 kPa, which is appropriate for PDMS-PDMS bonding, whereas the Reynolds number is near 1.91k in the laminar regime. No leakage or bubble occurred during the experimental validation, which suggests an appropriate pressure and a laminar flow in the channel.

RevDate: 2023-12-11

Srivathsan B, G T, Ram KV, et al (2023)

Multiphase simulation of sustainable nanoenhanced ionic liquid coolants for improved thermal performance in Ti-6Al-4V alloy drilling.

Heliyon, 9(12):e23020.

Extensive research has been conducted by the manufacturing industry to enhance the efficiency of drilling processes by focusing on the utilization of nanoenhanced cutting fluids that possess excellent heat conductivity. Due to their eco-friendliness and adaptability of physical and chemical properties, ionic fluids offer enormous potential for application as cutting fluids. This study investigates the computational fluid dynamics analysis of the heat transfer performance of various ionanofluid pairs dispersed with nanoparticles as cutting fluids in the drilling process using Ansys Fluent software. For this purpose, 1-Hexyl-3-methyl-imidazolium-tetrafluoroborate is considered the ionic fluid, and its thermal behavior is examined by dispersing it with nanoparticles of copper, silver, and multiwalled carbon nanotubes (MWCNT) at different particle volume fractions and Reynolds numbers. The workpiece is composed of an alloy of titanium Ti-6Al-4V, while the drill bit is made of tungsten carbide-cobalt. It is observed that the ionic nanocoolant mist emanates from the spray tip and moves towards the drill bit-workpiece interface. Initially, the coolant's velocity is greatest close to the orifice, and as time passes, it approaches the drilling space. The data indicates that the spraying velocity of the coolant augments over time and that it disperses heat at the tool-chip interface. The results help us validate the flow and interaction of ionanocoolant with the drilling zone. With a rise in the volume fraction of added nanoparticles and Reynolds number, the results indicated a significant decrease in the drilling temperature. With a higher particle volume fraction, the MWCNT-ionic coolant combination decreases the drilling temperature of pure ionic liquid by 25.64 %. The copper, silver, and MWCNT ionanofluids enhance the average heat transfer coefficient of pure ionic coolant by 35.14 %, 47.42 %, and 62.75 %, respectively. In addition, MWCNT nanocoolants demonstrated improved thermal performance and heat removal rate in comparison to copper and silver ionanocoolants.

RevDate: 2023-12-09

Ahmadi Azar A, Jalili B, Jalili P, et al (2023)

Investigating the effect of structural changes of two stretching disks on the dynamics of the MHD model.

Scientific reports, 13(1):21833.

The purpose of this theoretical study is to explore the behavior of an electrically conducting micropolar fluid when subjected to a uniform magnetic field along the vertical axis between two stretching disks as the structure of the problem changes. In this context, structural changes refer to alterations in the distance between the two discs or the stretching rate of the two discs. The governing equations of this problem are a set of nonlinear coupled partial differential equations, which are transformed into a nonlinear coupled ordinary differential equation set by a similarity transformation. The transformation results in four dimensionless quantities and their derivatives that appear in the equations. Nine dimensionless parameters are derived via similarity variables, including stretching Reynolds number, magnetic parameter, radiation parameter, Prandtl number, Eckert number, Schmidt number, and three micropolar parameters. Previous similarity solutions focused on analyzing the effect of changes in each parameter on the four dimensionless quantities. However, this type of analysis is mainly mathematical and does not provide practical results. This study's primary novelty is to redefine the magnetic parameter, Eckert number, stretching Reynolds number, and two micropolar parameters to analyze physical parameters that depend on the stretching rate of the two discs or the distance between them. The semi-analytical hybrid analytical and numerical method (HAN-method) is used to solve the equations. The results demonstrate that structural changes affect all five quantities of radial velocity, axial velocity, microrotation, temperature, and concentration. The study's most significant finding is that an increase in the stretching rate of the two disks causes a sharp increase in temperature and Nusselt number. Conversely, increasing the distance between the two disks causes a sharp decrease in micro-rotation and wall couple stress. They were compared to a previous study in a specific case to validate the results' accuracy.

RevDate: 2023-12-07

Alqarni MM, Memon AA, Memon MA, et al (2023)

Numerical investigation of heat transfer and fluid flow characteristics of ternary nanofluids through convergent and divergent channels.

Nanoscale advances, 5(24):6897-6912.

The characteristics of nanomaterials have garnered significant attention in recent research on natural and forced convection. This study focuses on the forced convection characteristics of ternary nanofluids within convergent and divergent channels. The ternary nanofluid comprises titanium oxide (TiO2), zinc oxide (ZnO), and silver suspended in water, which serves as the base fluid. Using COMSOL Multiphysics 6.0, a reliable software for finite element analysis, numerical simulations were conducted for steady and incompressible two-dimensional flow. Reynolds numbers varying from 100 to 800 were employed to investigate forced convection. Additionally, we explored aspect ratios (channel height divided by the height of the convergent or divergent section) of -0.4, -0.2, 0, 0.2, and 0.4. Our findings revealed that only at aspect ratio a = 0.4 did the average outlet temperature increase as the Reynolds number rose, while other aspect ratios exhibited decreasing average temperatures with declining Reynolds numbers. Moreover, as the Reynolds number increased from 100 to 800 and the total volume fraction of the ternary nanofluids ranged from 0.003 to 0.15, there was a significant 100% enhancement in the average Nusselt number. For clarity, this article briefly presents essential information, such as the study's numerical nature, fluid properties (constant-property fluid), and the methodology (COMSOL Multiphysics 6.0, finite element analysis). Key conclusions are highlighted to enable readers to grasp the main outcomes at a glance. These details are also adequately covered in the manuscript to facilitate a comprehensive understanding of the research. The utilization of this emerging phenomenon holds immense potential in various applications, ranging from the development of highly efficient heat exchangers to the optimization of thermal energy systems. This phenomenon can be harnessed in scenarios in which effective cost management in thermal production is a critical consideration.

RevDate: 2023-12-04

Wang Q, Pang Z, Tian C, et al (2023)

New Design Method of a Supersonic Steam Injection Nozzle and Its Numerical Simulation Verification.

ACS omega, 8(47):44485-44496.

Steam huff-n-puff in horizontal wells often had limitations, such as uneven steam injection and low reservoir utilization. To improve steam injection efficiency, a new method for designing a supersonic nozzle was proposed based on the principles of aerodynamics and thermodynamics. The nozzle featured a tapering section, a throat, and a diverging section. The best geometric shape of the tapering section was the Witoszynski curve. A set of nozzle size designs were established, and the size parameters were optimized. The results showed that the nozzle could inject steam into the formation at supersonic speed and it had the characteristics of constant flow rate and uniform development of the steam chamber. According to the steam Reynolds number and the good aggregation distribution characteristics of the size design model, three sequential nozzles of 3.0, 5.0, and 6.5 mm were formed based on the throat. When the throat diameter was 5.0 mm, the tapering length was 4.3 mm, the diverging length was 5.5 mm, the throat length was 3.0 mm, the inlet diameter was 9.8 mm, and the outlet diameter was 6.2 mm. Numerical simulations indicated that the pressure drop loss during steam huff-n-puff injection in horizontal wells was within 10%. It was of great significance to establish the nozzle size design model of the steam injection effect of horizontal wells.

RevDate: 2023-12-03

Liu X, Zhao Z, Xu S, et al (2023)

Meta-Lens Particle Image Velocimetry.

Advanced materials (Deerfield Beach, Fla.) [Epub ahead of print].

Fluid flow behavior is visualized through particle image velocimetry (PIV) for understanding and studying experimental fluid dynamics. However, traditional PIV methods require multiple cameras and conventional lens systems for image acquisition to resolve multi-dimensional velocity fields. In turn, it introduces complexity to the entire system. Meta-lenses are advanced flat optical devices composed of artificial nanoantenna arrays. It can manipulate the wavefront of light with advantages of ultrathin, compact, and no spherical aberration. Meta-lenses offer novel functionalities and promise to replace traditional optical imaging systems. Here, we propose a binocular meta-lens PIV technique, where a pair of GaN meta-lenses are fabricated on one substrate and integrated with a CMOS sensor to form a compact binocular PIV system. The meta-lens weigh only 116 mg, much lighter than commercial lenses. The three-dimensional velocity field can be obtained by the binocular disparity and particle image displacement information of fluid flow. The measurement error of vortex-ring diameter is about 1.25% experimentally validated via a Reynolds-number 2000 vortex-ring. This work demonstrates a new development trend for the PIV technique for rejuvenating traditional flow diagnostic tools towards a more compact, easy-to-deploy technique. It enables further miniaturization and low-power systems for portable, field-use, and space-constrained PIV applications. This article is protected by copyright. All rights reserved.

RevDate: 2023-12-01

Buaria D, KR Sreenivasan (2023)

Saturation and Multifractality of Lagrangian and Eulerian Scaling Exponents in Three-Dimensional Turbulence.

Physical review letters, 131(20):204001.

Inertial-range scaling exponents for both Lagrangian and Eulerian structure functions are obtained from direct numerical simulations of isotropic turbulence in triply periodic domains at Taylor-scale Reynolds number up to 1300. We reaffirm that transverse Eulerian scaling exponents saturate at ≈2.1 for moment orders p≥10, significantly differing from the longitudinal exponents (which are predicted to saturate at ≈7.3 for p≥30 from a recent theory). The Lagrangian scaling exponents likewise saturate at ≈2 for p≥8. The saturation of Lagrangian exponents and transverse Eulerian exponents is related by the same multifractal spectrum by utilizing the well-known frozen hypothesis to relate spatial and temporal scales. Furthermore, this spectrum is different from the known spectra for Eulerian longitudinal exponents, suggesting that Lagrangian intermittency is characterized solely by transverse Eulerian intermittency. We discuss possible implications of this outlook when extending multifractal predictions to the dissipation range, especially for Lagrangian acceleration.

RevDate: 2023-11-30

Abd-Alla AM, Abo-Dahab SM, Salah DM, et al (2023)

Magneto-hydrodynamic peristaltic flow of a Jeffery fluid in the presence of heat transfer through a porous medium in an asymmetric channel.

Scientific reports, 13(1):21088.

In the present paper, the effects of magnetic field and heat transfer on the peristaltic flow of a Jeffery fluid through a porous medium in an asymmetric channel have been studied. The governing non-linear partial differential equations representing the flow model are transmuted into linear ones by employing the appropriate non-dimensional parameters under the assumption of long wavelength and low Reynolds number. Exact solutions are presented for the stream function, pressure gradient, and temperature. The frictional force and pressure rise are both computed using numerical integration. Using MATLAB R2023a software, a parametric analysis is performed, and the resulting data is represented graphically. For all physical quantities considered, numerical calculations were made and represented graphically. Trapping phenomena are discussed graphically. The obtained results can be applied to enhance pumping systems in engineering and gastrointestinal functions. This analysis permits body fluids such as blood and lymph to easily move inside the arteries and veins, allowing oxygen supply, waste elimination, and other necessary elements.

RevDate: 2023-11-30

Ahmad S, Ali K, Castellanos HG, et al (2023)

Complex dynamics of induced vortex formation and thermal-fluid coupling in tri-hybrid nanofluid under localized magnetic field: a novel study.

Scientific reports, 13(1):21140.

Hybrid nanofluids offer higher stability, synergistic effects, and better heat transfer compared to simple nanofluids. Their higher thermal conductivity, lower viscosity, and interaction with magnetic fields make them ideal for various applications, including materials science, transportation, medical technology, energy, and fundamental physics. The governing partial differential equations are numerically solved by employing a finite volume approach, and the effects of various parameters on the nanofluid flow and thermal characteristics are systematically examined from the simulations based on a self-developed MATLAB code. The parameters included magnetic field strength, the Reynolds number, the nanoparticle volume fraction, and the number and position of the strips in which the magnetic field is localized. It has been noted that the magnetized field induces the spinning of the tri-hybrid nanoparticles, which generates the intricate structure of vortices in the flow. The local skin friction (CfRe) and the Nusselt number (Nu) increase significantly when the magnetic field is intensified. Moreover, adding more nanoparticles in the flow enhances both Nu and CfRe, but with different effects for different nanoparticles. Silver (Ag) shows the highest increase in both Nu (52%) and CfRe (110%), indicating strong thermal-fluid coupling. Alumina (Al2O3) and Titanium Dioxide (TiO2) show lower increases in both Nu (43% and 34%) and CfRe (14% and 10%), indicating weaker coupling in the flow. Finally, compared with the localized one, the uniform magnetic field has a minor effect on the flow and temperature distributions.

RevDate: 2023-11-30

Han J, H Lee (2023)

Control Volume Analysis of the Infusion Rate in Cephalic and Median Cubital Veins Based on Infusion Bag Height and Peripheral Venous Catheter Inner Diameter: Application of Bernoulli's Equation and Consideration of Frictional Forces.

Journal of multidisciplinary healthcare, 16:3609-3618 pii:409050.

PURPOSE: This pilot study aimed to provide basic data on intravenous infusion nursing by analyzing the infusion rate in the cephalic and median cubital veins depending on the height of the infusion bag and inner diameter of the peripheral venous catheter (PVC).

METHODS: While infusing 0.9% normal saline at 22 °C (room temperature) into elbow cephalic and median cubital veins, the infusion rate may be controlled by adjusting the fluid height and PVC diameter. To assess the validity of the laminar flow assumption, the study estimated the Reynolds number (Re) using the velocity obtained by applying Bernoulli's equation considering the friction coefficient.

RESULTS: At a constant fluid height, the infusion rate increased with increasing PVC diameter. At a constant PVC diameter, the infusion rate increased with increasing fluid height. In a comparison between the cephalic and median cubital veins at constant fluid height and PVC diameter, the solution was infused at a higher rate into the cephalic vein, which was under lower venous pressure.

CONCLUSION: The analysis of the infusion rate according to fluid height and PVC diameter provided basic data on intravenous infusion nursing. The results are expected to provide evidence for the standardization of intravenous infusion nursing.

RevDate: 2023-11-29

Jamil DF, Uddin S, Kazi M, et al (2023)

MHD blood flow effects of Casson fluid with Caputo-Fabrizio fractional derivatives through an inclined blood vessels with thermal radiation.

Heliyon, 9(11):e21780 pii:S2405-8440(23)08988-0.

This study investigates a fractional-order time derivative model of non-Newtonian magnetic blood flow in the presence of thermal radiation and body acceleration through an inclined artery. The blood flow is formulated using the Casson fluid model under the control of a uniformly distributed magnetic field and an oscillating pressure gradient. Caputo-Fabrizio's fractional derivative mathematical model was used, along with Laplace transform and the finite Hankel transform technique. Analytical expressions were obtained for the velocity of blood flow, magnetic particle distribution, and temperature profile. These distributions are presented graphically using Mathcad software. The results show that the velocity increases with the time, Reynolds number and Casson fluid parameters, and diminishes when Hartmann number increases. Moreover, fractional parameters, radiation values, and metabolic heat source play an essential role in controlling the blood temperature. More precisely, these results are beneficial for the diagnosis and treatment of certain medical issues.

RevDate: 2023-11-29

Alklaibi AM, Chandra Mouli KVV, L Syam Sundar (2023)

Experimental and support vector machine predictions of entropy generations and exergy efficiency of Fe3O4-SiO2/Water hybrid nanofluid in a plate heat exchanger.

Heliyon, 9(11):e21730 pii:S2405-8440(23)08938-7.

Several experiments of Fe3O4-SiO2/water hybrid nanofluids with volumetric concentrations ranging from 0.2 % to 1.0 % circulating in the cold-side of a plate heat exchanger at flow rates ranging from 0.05 kg/s to 0.1166 kg/s are performed. Under these ranges of flow rates and volumetric concentrations, the flow of Fe3O4-SiO2/water hybrid nanofluids remains laminar. The results of these experiments are predicted with support vector machine (SVM) algorithm to determine hybrid nanofluid entropy generation thermal, entropy generation frictional, and efficiency of exergy. Fe3O4-SiO2 nanomaterials was synthesized with reduction of chemicals and insitu development techniques, with XRD, FTIR and VSM instruments, characterizations were done. The SVM model gives large precision predictions of the measured data with correlations coefficients of 0.9944, 0.99798, and 0.99428 for frictional entropy generation, thermal entropy generation and exergy efficiency. At a flow rate of 0.1166 kg/s in the cold-side of PHE, the exergy efficiency is found to be 77.96 % for water (Reynolds number of 935.4) and with 1.0 vol% of Fe3O4-SiO2/water hybrid nanofluid in the cold-side of PHE, the efficiency is increased to 82.97 %, respectively. Under similar conditions of 0.1166 kg/s of flow circulation and 1.0 % vol. concentration of hybrid nanofluid, the thermal entropy generation is dropped off to 18.37 %, but the frictional entropy generation is increased by 20.97 %, compared to water, with the results that the total entropy generation drops off by 15.91 %, compared to water data. Preliminary curve-fitting correlations have been developed for the frictional entropy generation, thermal entropy generation, and exergy efficiency.

RevDate: 2023-11-25

Krauter N, F Stefani (2023)

Simultaneous Measurement of Flow Velocity and Electrical Conductivity of a Liquid Metal Using an Eddy Current Flow Meter in Combination with a Look-Up-Table Method.

Sensors (Basel, Switzerland), 23(22): pii:s23229018.

The Eddy Current Flow Meter (ECFM) is a commonly employed inductive sensor for assessing the local flow rate or flow velocity of liquid metals with temperatures up to 700 ∘C. One limitation of the ECFM lies in its dependency on the magnetic Reynolds number for measured voltage signals. These signals are influenced not only by the flow velocity but also by the electrical conductivity of the liquid metal. In scenarios where temperature fluctuations are significant, leading to corresponding variations in electrical conductivity, it becomes imperative to calibrate the ECFM while concurrently monitoring temperature to discern the respective impacts of flow velocity and electrical conductivity on the acquired signals. This paper introduces a novel approach that enables the concurrent measurement of electrical conductivity and flow velocity, even in the absence of precise knowledge of the liquid metal's conductivity or temperature. This method employs a Look-Up-Table methodology. The feasibility of this measurement technique is substantiated through numerical simulations and further validated through experiments conducted on the liquid metal alloy GaInSn at room temperature.

RevDate: 2023-11-25

Borbas SW, Shen K, Ji C, et al (2023)

Transit Time Theory for a Droplet Passing through a Slit in Pressure-Driven Low Reynolds Number Flows.

Micromachines, 14(11): pii:mi14112040.

Soft objects squeezing through small apertures are crucial for many in vivo and in vitro processes. Red blood cell transit time through splenic inter-endothelial slits (IESs) plays a crucial role in blood filtration and disease progression, while droplet velocity through constrictions in microfluidic devices is important for effective manipulation and separation processes. As these transit phenomena are not well understood, we sought to establish analytical and numerical solutions of viscous droplet transit through a rectangular slit. This study extends from our former theory of a circular pore because a rectangular slit is more realistic in many physiological and engineering applications. Here, we derived the ordinary differential equations (ODEs) of a droplet passing through a slit by combining planar Poiseuille flow, the Young-Laplace equations, and modifying them to consider the lubrication layer between the droplet and the slit wall. Compared to the pore case, we used the Roscoe solution instead of the Sampson one to account for the flow entering and exiting a rectangular slit. When the surface tension and lubrication layer were negligible, we derived the closed-form solutions of transit time. When the surface tension and lubrication layer were finite, the ODEs were solved numerically to study the impact of various parameters on the transit time. With our solutions, we identified the impact of prescribed pressure drop, slit dimensions, and droplet parameters such as surface tension, viscosity, and volume on transit time. In addition, we also considered the effect of pressure drop and surface tension near critical values. For this study, critical surface tension for a given pressure drop describes the threshold droplet surface tension that prevents transit, and critical pressure for a given surface tension describes the threshold pressure drop that prevents transit. Our solutions demonstrate that there is a linear relationship between pressure and the reciprocal of the transit time (referred to as inverse transit time), as well as a linear relationship between viscosity and transit time. Additionally, when the droplet size increases with respect to the slit dimensions, there is a corresponding increase in transit time. Most notably, we emphasize the initial antagonistic effect of surface tension which resists droplet passage but at the same time decreases the lubrication layer, thus facilitating passage. Our results provide quantitative calculations for understanding cells passing through slit-like constrictions and designing droplet microfluidic experiments.

RevDate: 2023-11-15

Rahman MT, Habib K, Quader MN, et al (2023)

Effect of porous density of twisted tape inserts on heat transfer performance inside a closed conduit.

Heliyon, 9(11):e21206 pii:S2405-8440(23)08414-1.

This study examines the impact of varying the porosity density of twisted tape inserts (TTI) on the temperature distribution, fluid velocities, heat transfer coefficients (HTC), Nusselt numbers (Nu), turbulent kinetic energy (TKE), and performance from 5000 to 12500 Reynolds numbers (Re). The entire process involved the design of TTIs and double pipe heat exchangers using SolidWorks. Subsequently, a three-dimensional fluid flow model was employed to solve equations related to energy mass, energy, and momentum within the ANSYS Fluent interfaces. The findings highlight the noteworthy impact of high porosity TTIs, which consistently reduce temperature spans, increase fluid velocities, and greatly HTC and Nu when compared to low porosity TTI, typical TTI, and plain tubes. Furthermore, high porosity TTI significantly increases TKE, indicating increased fluid turbulence and higher heat transfer efficiency, especially at Re = 12500. The assessment of PEC emphasizes the superiority of high porosity TTI, demonstrating their significant performance increase potential of over 6.44 % over low porosity TTI and a staggering 62.5 % above typical TTI. In conclusion, high porosity TTI emerges as a potential solution for improving heat transfer efficiency and overall system performance in a variety of industrial applications, promising enhanced energy efficiency and superior performance.

RevDate: 2023-11-14

Htet PH, E Lauga (2023)

Cortex-driven cytoplasmic flows in elongated cells: fluid mechanics and application to nuclear transport in Drosophila embryos.

Journal of the Royal Society, Interface, 20(208):20230428.

The Drosophila melanogaster embryo, an elongated multi-nucleated cell, is a classical model system for eukaryotic development and morphogenesis. Recent work has shown that bulk cytoplasmic flows, driven by cortical contractions along the walls of the embryo, enable the uniform spreading of nuclei along the anterior-posterior axis necessary for proper embryonic development. Here, we propose two mathematical models to characterize cytoplasmic flows driven by tangential cortical contractions in elongated cells. Assuming Newtonian fluid flow at low Reynolds number in a spheroidal cell, we first compute the flow field exactly, thereby bypassing the need for numerical computations. We then apply our results to recent experiments on nuclear transport in cell cycles 4-6 of Drosophila embryo development. By fitting the cortical contractions in our model to measurements, we reveal that experimental cortical flows enable near-optimal axial spreading of nuclei. A second mathematical approach, applicable to general elongated cell geometries, exploits a long-wavelength approximation to produce an even simpler solution, with errors below [Formula: see text] compared with the full model. An application of this long-wavelength result to transport leads to fully analytical solutions for the nuclear concentration that capture the essential physics of the system, including optimal axial spreading of nuclei.

RevDate: 2023-11-13

Bureau L, Coupier G, T Salez (2023)

Lift at low Reynolds number.

The European physical journal. E, Soft matter, 46(11):111.

Lift forces are widespread in hydrodynamics. These are typically observed for big and fast objects and are often associated with a combination of fluid inertia (i.e. large Reynolds numbers) and specific symmetry-breaking mechanisms. In contrast, the properties of viscosity-dominated (i.e. low Reynolds numbers) flows make it more difficult for such lift forces to emerge. However, the inclusion of boundary effects qualitatively changes this picture. Indeed, in the context of soft and biological matter, recent studies have revealed the emergence of novel lift forces generated by boundary softness, flow gradients and/or surface charges. The aim of the present review is to gather and analyse this corpus of literature, in order to identify and unify the questioning within the associated communities, and pave the way towards future research.

RevDate: 2023-11-12

Lordifard P, Shariatpanahi SP, Khajeh K, et al (2023)

Frequency dependence of ultrasonic effects on the kinetics of hen egg white lysozyme fibrillation.

International journal of biological macromolecules pii:S0141-8130(23)04770-0 [Epub ahead of print].

Our study aimed to investigate the effects of ultrasound on the fibrillation kinetics of HEWL (hen egg white lysozyme) and its physicochemical properties. Ultrasound, a mechanical wave, can induce conformational changes in proteins. To achieve this, we developed an ultrasound exposure system and used various biophysical techniques, including ThT fluorescence spectroscopy, ATR-FTIR, Far-UV CD spectrophotometry, Fluorescence microscopy, UV-spectroscopy, and seeding experiments. Our results revealed that higher frequencies significantly accelerated the fibrillation of lysozyme by unfolding the native protein and promoting the fibrillation process, thereby reducing the lag time. We observed a change in the secondary structure of the sonicated protein change to the β-structure, but there was no difference in the Tm of native and sonicated proteins. Furthermore, we found that higher ultrasound frequencies had a greater seeding effect. We propose that the effect of frequency can be explained by the impact of the Reynolds number, and for the Megahertz frequency range, we are almost at the transition regime of turbulence. Our results suggest that laminar flows may not induce any significant change in the fibrillation kinetics, while turbulent flows may affect the process.

RevDate: 2023-11-09

Abdalkarem AAM, Ansaf R, Muzammil WK, et al (2023)

Preliminary assessment of the NACA0021 trailing edge wedge for wind turbine application.

Heliyon, 9(11):e21193.

The airfoil blade is the primary component of a wind turbine, and its aerodynamic properties play a crucial role in determining the energy conversion efficiency of these blades. Many researchers have proposed different airfoil modifications intending to enhance the aerodynamic characteristics and limit the unsteady interaction with the atmospheric boundary layer. This study evaluates the benefits of mounting wedge tails (WTs) on the trailing edge of an airfoil. The aerodynamic characteristics of a 2-D, steady-state NACA 0021 airfoil featuring the wedge tails (WT) and fish wedge tails (FWT) were studied computationally by employing the shear stress transport (SST) k-ω turbulence model. Different WT and FWT configurations were studied at various wedge length (L) to wedge height (H) ratios, L/H, at the airfoil's trailing edge. The effects of different L/H ratios, including L/H > 1, L/H = 1, and L/H < 1, were considered in the present study to determine the optimal configuration to achieve the maximum glide ratio, CL/CD at the Reynolds number of 180,000. The findings indicate that the performance of the NACA 0021 airfoil was notably affected by the height of the tail; however, the length had only a minor impact when L/H was less than 1. The mounted FWT resulted in significant enhancements to both the lift and glide ratio of the airfoil. Specifically, the lift ratio experienced an increase of over 41 % compared to the clean airfoil, while the glide ratio increased by more than 31 %. These improvements were observed at an ideal height and length of 2.5 % and 1 % of the airfoil, respectively. Moreover, the mounted FWT performed better than the Gurney flap using the same configurations.

RevDate: 2023-11-08

Fercak O, Lyons K, Murphy CT, et al (2023)

Multicolor dye-based flow structure visualization for seal-whisker geometry characterized by computer vision.

Bioinspiration & biomimetics [Epub ahead of print].

Pinniped vibrissae possess a unique and complex three-dimensional topography, which has beneficial fluid flow characteristics such as substantial reductions in drag, lift, and vortex induced vibration. To understand and leverage these effects, the downstream vortex dynamics must be studied. Dye visualization is a traditional qualitative method of capturing these downstream effects, specifically in comparative biological investigations where complex equipment can be prohibitive. High-fidelity numerical simulations or experimental particle image velocimetry (PIV) are commonplace for quantitative high-resolution flow measurements, but are computationally expensive, require costly equipment, and can have limited measurement windows. This study establishes a method for extracting quantitative data from standard dye visualization experiments on seal whisker geometries by leveraging novel but intuitive computer vision techniques, which maintain simplicity and an advantageous large experimental viewing window while automating the extraction of vortex frequency, position, and advection. Results are compared to direct numerical simulation (DNS) data for comparable geometries. Power spectra and Strouhal numbers show consistent behavior between methods for a Reynolds number of 500, with minima at the canonical geometry wavelength of 3.43 and a peak frequency of 0.2 for a Reynolds number of 250. The vortex tracking reveals a clear increase in velocity from roll-up to 3.5 whisker diameters downstream, with a strong overlap with the DNS data but shows steady results beyond the limited DNS window. This investigation provides insight into a valuable bio-inspired engineering model while advancing an analytical methodology that can readily be applied to a broad range of comparative biological studies.

RevDate: 2023-11-06

Gjerde IG, Rognes ME, AL Sánchez (2023)

The directional flow generated by peristalsis in perivascular networks-Theoretical and numerical reduced-order descriptions.

Journal of applied physics, 134(17):174701.

Directional fluid flow in perivascular spaces surrounding cerebral arteries is hypothesized to play a key role in brain solute transport and clearance. While various drivers for a pulsatile flow, such as cardiac or respiratory pulsations, are well quantified, the question remains as to which mechanisms could induce a directional flow within physiological regimes. To address this question, we develop theoretical and numerical reduced-order models to quantify the directional (net) flow induceable by peristaltic pumping in periarterial networks. Each periarterial element is modeled as a slender annular space bounded internally by a circular tube supporting a periodic traveling (peristaltic) wave. Under reasonable assumptions of a small Reynolds number flow, small radii, and small-amplitude peristaltic waves, we use lubrication theory and regular perturbation methods to derive theoretical expressions for the directional net flow and pressure distribution in the perivascular network. The reduced model is used to derive closed-form analytical expressions for the net flow for simple network configurations of interest, including single elements, two elements in tandem, and a three element bifurcation, with results compared with numerical predictions. In particular, we provide a computable theoretical estimate of the net flow induced by peristaltic motion in perivascular networks as a function of physiological parameters, notably, wave length, frequency, amplitude, and perivascular dimensions. Quantifying the maximal net flow for specific physiological regimes, we find that vasomotion may induce net pial periarterial flow velocities on the order of a few to tens of μm/s and that sleep-related changes in vasomotion pulsatility may drive a threefold flow increase.

RevDate: 2023-11-03

Vakilabadi KA, Ghafari HR, H Ghassemi (2023)

Experimental and numerical investigation on a trimaran airwake, geometry modification.

Heliyon, 9(11):e21144 pii:S2405-8440(23)08352-4.

The aerodynamic interaction between a helicopter and a trimaran ship's flight deck can be complex and have an impact on handling quality and performance, especially in turbulent conditions. This article presents research on the flight deck geometry of a trimaran vessel without the presence of a helicopter. Both Particle Image Velocimetry (PIV) and computational fluid dynamics (CFD) were used to analyze the effect of wind velocity on air pressure in the flight deck region. The study proposed and evaluated different geometries of the top structure at several air velocities to minimize pressure differences. The results of the numerical simulation were validated by experimental measurements using PIV, which showed that the effect of the Reynolds number on the non-dimensional pressure near the top structure is negligible except for the biggest Reynolds number (Re = 50e6), while at x/L = 0.5 the significant difference can be seen, however, the same result found for Re = 38e6 and 50e6. At the farthest distance (x/L = 1), the pressure difference for different Reynolds numbers case studies is negligible. Among the various geometries assessed, the maximum non-dimensional pressure differences along the lines show the highest value occurs for the base geometry (A) while geometries C and F show lower values, which have chamfering along the middle and side horizontal edges at a 45-degree angle and chamfering along all vertical and horizontal edges at a 30-degree angle.

RevDate: 2023-11-02

Zhou ZL, Zhu LF, Li TX, et al (2023)

Sub-satisfactory stenting recanalization of severe vascular stenosis of the posterior circulation can significantly improve cerebral hemodynamic perfusion.

European journal of radiology, 169:111135 pii:S0720-048X(23)00449-7 [Epub ahead of print].

PURPOSE: To investigate the effect of sub-satisfactory stenting recanalization of severe vascular stenosis of the posterior circulation on cerebral hemodynamic perfusion.

MATERIALS AND METHODS: Patients with severe vascular stenosis of the posterior circulation who had undergone three-dimensional cerebral angiography before and after stenting were retrospectively enrolled. Computational fluid dynamic (CFD) analysis of hemodynamic parameters at the stenosis, perforating branch, and normal arterial segments proximal and distal to the stenosis were performed.

RESULTS: Sixty-two patients with basilar artery stenosis aged 60.9 ± 9.6 years were enrolled, and stent angioplasty resulted in the reduction of stenosis degree from 85.3 ± 7.2% before to 18.6 ± 6.4% after stenting. After stenting, at the proximal normal artery, the total pressures had significantly (P < 0.05) decreased, whereas all the other parameters (WSS, cell Reynolds number, velocity, vorticity, turbulence intensity, turbulence kinetic energy and dissipation rate) had significantly (P < 0.05) increased. At the stenosis, all hemodynamic parameters had significantly decreased. At the stenosis perforating branch, the WSS, cell Reynolds number, velocity, and vorticity were all significantly decreased, and the total pressure, turbulence intensity, kinetic energy, and dissipation rate were all significantly increased. At the distal normal artery, the total flow pressure (perfusion pressure) and velocity were both significantly (P < 0.05) increased, and the total pressure, WSS, cell Reynolds number, vorticity, turbulence intensity, kinetic energy, and dissipation rate were all significantly (P < 0.05) decreased. The hemodynamic parameters after stenting were closer to those after virtual stenosis repair at all measurements.

CONCLUSION: Sub-satisfactory recanalization has significantly restored the stenosis and improved the hemodynamic parameters near the stenosis and at the root of the perforating branch, thus significantly improving the cerebral perfusion, similar to the changes of hemodynamic status and cerebral perfusion after virtual removal of the vascular stenosis. This may indicate the good effect of sub-satisfactory stenting recanalization of the vascular stenosis at the posterior circulation.

RevDate: 2023-11-02

Javaherchian J, Moosavi A, SA Tabatabaei (2023)

Numerical analysis of pressure drop reduction of bubbly flows through hydrophobic microgrooved channels.

Scientific reports, 13(1):18861.

Due to the high performance of hydrophobic surfaces in pressure drop reduction, they have been proposed for various applications. However, despite the extensive uses of two-phase flows in many industries, the effect of hydrophobic surfaces on the pressure drop reduction of two-phase flows has not been well understood yet. Thus, in the present study, by implementing the phase-field and finite element methods, the bubbly flows as an example of two-phase flows are considered for examining the effect of hydrophobic microgrooved microchannels on the pressure drop reduction of these regimes in the laminar state. We found out that hydrophobic microgrooved surfaces not only can be efficient in the bubbly flow but also can even cause a maximum pressure drop reduction of up to 70%, which is almost 3.5 times higher than in single-phase flow. We also studied the influence of each parameter, such as bubbles volume or length, Reynolds number, capillary number, and their combination on this phenomenon. The pressure drop reduction grows by increasing the volume of the bubbles but decreases by increasing the flow velocity or the surface tension coefficient. The combination of these parameters demonstrated different results in some circumstances.

RevDate: 2023-11-01

Zhao W, Shang X, Zhang B, et al (2023)

Squeezed state in the hydrodynamic focusing regime for Escherichia coli bacteria detection.

Lab on a chip [Epub ahead of print].

Flow cytometry is an essential technique in single particle analysis and cell sorting for further downstream diagnosis, exhibiting high-throughput and multiplexing capabilities for many biological and biomedical applications. Although many hydrodynamic focusing-based microfluidic cytometers have been demonstrated with reduced size and cost to adapt to point-of-care settings, the operating conditions are not characterized systematically. This study presents the flow transition process in the hydrodynamic focusing mechanism when the flow rate or the Reynolds number increases. The characteristics of flow fields and mass transport were studied under various operating conditions, including flow rates and microchannel heights. A transition from the squeezed focusing state to the over-squeezed anti-focusing state in the hydrodynamic focusing regime was observed when the Reynolds number increased above 30. Parametric studies illustrated that the focusing width increased with the Reynolds number but decreased with the microchannel height in the over-squeezed state. The microfluidic cytometric analyses using microbeads and E. coli show that the recovery rate was maintained by limiting the Reynolds number to 30. The detailed analysis of the flow transition will provide new insight into microfluidic cytometric analyses with a broad range of applications in food safety, water monitoring and healthcare sectors.

RevDate: 2023-10-31

Zöttl A, Tesser F, Matsunaga D, et al (2023)

Asymmetric bistability of chiral particle orientation in viscous shear flows.

Proceedings of the National Academy of Sciences of the United States of America, 120(45):e2310939120.

The migration of helical particles in viscous shear flows plays a crucial role in chiral particle sorting. Attaching a nonchiral head to a helical particle leads to a rheotactic torque inducing particle reorientation. This phenomenon is responsible for bacterial rheotaxis observed for flagellated bacteria as Escherichia coli in shear flows. Here, we use a high-resolution microprinting technique to fabricate microparticles with controlled and tunable chiral shape consisting of a spherical head and helical tails of various pitch and handedness. By observing the fully time-resolved dynamics of these microparticles in microfluidic channel flow, we gain valuable insights into chirality-induced orientation dynamics. Our experimental model system allows us to examine the effects of particle elongation, chirality, and head heaviness for different flow rates on the orientation dynamics, while minimizing the influence of Brownian noise. Through our model experiments, we demonstrate the existence of asymmetric bistability of the particle orientation perpendicular to the flow direction. We quantitatively explain the particle equilibrium orientations as a function of particle properties, initial conditions and flow rates, as well as the time-dependence of the reorientation dynamics through a theoretical model. The model parameters are determined using boundary element simulations, and excellent agreement with experiments is obtained without any adjustable parameters. Our findings lead to a better understanding of chiral particle transport and bacterial rheotaxis and might allow the development of targeted delivery applications.

RevDate: 2023-10-29

Jalili B, Shateri A, Akgül A, et al (2023)

An investigation into a semi-porous channel's forced convection of nano fluid in the presence of a magnetic field as a result of heat radiation.

Scientific reports, 13(1):18505.

This study investigates the impact of heat radiation on magnetically-induced forced convection of nanofluid in a semi-porous channel. The research employs Akbari-Ganji's and Homotopy perturbation methods to analyze the effects of multiple parameters, including Hartmann number, Reynolds number, Eckert number, radiation parameter, and suction parameter, on the flow and heat transfer characteristics. The results demonstrate that increasing Reynolds number, suction, and radiation parameters increases temperature gradient, providing valuable insights into improving heat transfer in semi-porous channels. The study validates the proposed methods by comparing the results with those obtained from other established methods in the literature. The main focus of this work is to understand the behavior of nanofluids in semi-porous channels under the influence of magnetic fields and heat radiation, which is essential for various industrial and engineering applications. The future direction of this research includes exploring the effects of different nanoparticle shapes and materials on heat transfer performance and investigating the influence of other parameters, such as buoyancy forces and variable properties, on the flow and heat transfer characteristics. The findings of this study are expected to contribute to the development of more efficient thermal management systems in the future.

RevDate: 2023-10-28

Zhao H, Ma H, Yan X, et al (2023)

Investigation of Hydrothermal Performance in Micro-Channel Heat Sink with Periodic Rectangular Fins.

Micromachines, 14(10): pii:mi14101818.

The micro-channel heat sink (MCHS) is an excellent choice due to its exceptional cooling capabilities, surpassing those of its competitors. In this research paper, a computational fluid dynamics analysis was performed to investigate the laminar flow and heat transfer characteristics of five different configurations of a variable geometry rectangular fin. The study utilized a water-cooled smooth MCHS as the basis. The results indicate that the micro-channel heat sink with a variable geometry rectangular fin has better heat dissipation capacity than a straight-type micro-channel heat sink, but at the same time, it has larger pressure loss. Based on the analysis of various rectangular fin shapes and Reynolds numbers in this study, the micro-channel heat sink with rectangular fins exhibits Nusselt numbers and friction factors that are 1.40-2.02 and 2.64-4.33 times higher, respectively, compared to the smooth heat sink. This significant improvement in performance results in performance evaluation criteria ranging from 1.23-1.95. Further, it is found that at a relatively small Reynolds number, the micro-channel heat sink with a variable geometry rectangular fin has obvious advantages in terms of overall cooling performance. Meanwhile, this advantage will decrease when the Reynolds number is relatively large.

RevDate: 2023-10-27

Vaferi K, Vajdi M, Nekahi S, et al (2023)

Thermo-hydraulic performance optimization of a disk-shaped microchannel heat sink applying computational fluid dynamics, artificial neural network, and response surface methodology.

Heliyon, 9(10):e21031.

The current research focuses on optimizing the Nusselt number (Nu) and pressure drop (ΔP) in a bionic fractal heat sink. The artificial neural network (ANN) and response surface methodology (RSM) were used to model the thermos-hydraulic behavior of the MCHS. The aspect ratios of t/b (cavities' upper side to bottom side ratio) and h/b (cavities' height to bottom side ratio), as well as the Reynolds number, were set as the independent variables in both ANN and RSM models. After finding the optimum state for the copper-made MCHS (containing the optimum design of the cavities along with the best applied velocity), different materials were tested and compared with the base case (heat sink made of copper). The obtained results indicated that both ANN and RSM models (with determination coefficient of 99.9 %) could exactly anticipate heat transfer and ΔP to a large extent. To achieve the optimal design of the microchannel heat sink (MCHS) with the objective of maximizing Nu and minimizing ΔP, the efficiency index of the device was evaluated. The analysis revealed that the highest efficiency index (1.070 by RSM and 1.067 by ANN methods) was attained when the aspect ratios were t/b = 0.2, h/b = 0.2, and the Reynolds number was 1000. Next, the effect of the different materials on heat sink performance was investigated, and it was observed that by reducing the thermal conductivity, the thermal resistance of the heat sink increased and its overall performance decreased.

RevDate: 2023-10-18

Paludan MV, Biviano MD, KH Jensen (2023)

Elastohydrodynamic autoregulation in soft overlapping channels.

Physical review. E, 108(3-2):035106.

Controlling fluid flow from an unsteady source is a challenging problem that is relevant in both living and man-made systems. Animals have evolved various autoregulatory mechanisms to maintain homeostasis in vital organs. This keeps the influx of nutrients essentially constant and independent of the perfusion pressure. Up to this point, the autoregulation processes have primarily been ascribed to active mechanisms that regulate vessel size, thereby adjusting the hydraulic conductance in response to, e.g., sensing of wall shear stress. We propose an alternative elastohydrodynamic mechanism based on contacting soft vessels. Inspired by Starling's resistor, we combine experiments and theory to study the flow of a viscous liquid through a self-intersecting soft conduit. In the overlapping region, the pressure difference between the two channel segments can cause one pipe segment to dilate while the other is compressed. If the tissue is sufficiently soft, this mode of fluid-structure interactions can lead to flow autoregulation. Our experimental observations compare well to a predictive model based on low-Reynolds-number fluid flow and linear elasticity. Implications for conduit arrangement and passive autoregulation in organs and limbs are discussed.

RevDate: 2023-10-18

Xing Y, Burdsall AC, Owens A, et al (2021)

The effect of mixing and free-floating carrier media on bioaerosol release from wastewater: a multiscale investigation with Bacillus globigii.

Environmental science : water research & technology, 7:.

Aeration tanks in wastewater treatment plants (WWTPs) are significant sources of bioaerosols, which contain microbial contaminants and can travel miles from the site of origin, risking the health of operators and the general public. One potential mitigation strategy is to apply free-floating carrier media (FFCM) to suppress bioaerosol emission. This article presents a multiscale study on the effects of mixing and FFCM on bioaerosol release using Bacillus globigii spores in well-defined liquid media. Bioaerosol release, defined as percentage of spores aerosolized during a 30 minute sampling period, ranged from 6.09 × 10[-7]% to 0.057%, depending upon the mixing mode and intensity. Bioaerosol release increased with the intensity of aeration (rotating speed in mechanical agitation and aeration rate in diffused aeration). A surface layer of polystyrene beads reduced bioaerosol released by >92% in the bench-scale studies and >74% in the pilot-scale study. This study discovered strong correlations (R[2] > 0.82) between bioaerosol release and superficial gas velocity, Froude number, and volumetric gas flow per unit liquid volume per minute. The Reynolds number was found to be poorly correlated with bioaerosol release (R[2] < 0.5). This study is a significant step toward the development of predictive models for full scale systems.

RevDate: 2023-10-17

Maruai NM, Ali MSM, Zaki SA, et al (2023)

The influence of different downstream plate length towards the flow-induced vibration on a square cylinder.

Scientific reports, 13(1):17681.

The investigations of flow-induced vibration have been around for decades to solve many engineering problems related to structural element. In a hindsight of advancing technology of microelectronics devices, the implementation of flow-induced vibration for energy harvesting is intrigued. The influence of downstream flat plate to flow-induced vibration experienced by a square cylinder is discussed in this study to surpass the limitation of wind energy due to geographical constraints and climate change. The mechanism of flow-induced vibration experienced by a square cylinder with downstream flat plate is numerically simulated based on the unsteady Reynolds Navier-Stokes (URANS) flow field. The Reynolds number, Re assigned in this study is ranging between [Formula: see text]-[Formula: see text] and the mass damping ratio designated for the square cylinder is [Formula: see text] = 2.48. The influence of three different flat plate lengths [Formula: see text], 1 and 3 is examined. Each case of different flat plate is explored for gap separation between the square cylinder and the plate in the range [Formula: see text]. Based on the numerical findings, the configuration of cylinder-flat plate with length [Formula: see text] has shown the highest potential to harvest high energy at comparatively low reduced velocity.

RevDate: 2023-10-12

Akram M, Memon AA, Memon MA, et al (2023)

Investigation of a two-dimensional photovoltaic thermal system using hybrid nanofluids and a rotating cylinder.

Nanoscale advances, 5(20):5529-5542.

This article focuses on a numerical investigation aimed at enhancing the electrical performance of a two-dimensional photovoltaic thermal system (PV/T) through the application of cooling using hybrid nanofluids. The hybrid nanofluids consist of titanium oxide and silver nanoparticles suspended in water, while the PV/T system is based on polycrystalline silicon, copper, and a flow channel with a rotating cylinder. PV/T devices generate electricity from sunlight, but their performance degrades over time due to the heat generated by solar radiation. Therefore, nanofluids can be circulated through the bottom flow channel to cool the device. This study utilizes 2D incompressible Navier-Stokes equations to control fluid flow and energy equations to manage energy distribution. The COMSOL 6.0 finite element software is employed for comprehensive modeling and simulation. To enhance the performance of the PV/T system, a parametric study is conducted by varying the Reynolds number (ranging from 100 to 1000), cylinder rotational speed (varying from 0.01 to 0.2 m s[-1]), and silver volume fraction (ranging from 0.01 to 0.2). The results show that increasing the Reynolds number and the volume fraction of silver leads to a reduction in the maximum temperature of the cell. The maximum temperature of the cell also decreases with the rotational speed of the cylinder but only for high Reynolds numbers. By applying the present model, the cell's efficiency is improved by 5.93%.

RevDate: 2023-10-12

Sutton GP, Szczecinski NS, Quinn RD, et al (2023)

Phase shift between joint rotation and actuation reflects dominant forces and predicts muscle activation patterns.

PNAS nexus, 2(10):pgad298.

During behavior, the work done by actuators on the body can be resisted by the body's inertia, elastic forces, gravity, or viscosity. The dominant forces that resist actuation have major consequences on the control of that behavior. In the literature, features and actuation of locomotion, for example, have been successfully predicted by nondimensional numbers (e.g. Froude number and Reynolds number) that generally express the ratio between two of these forces (gravitational, inertial, elastic, and viscous). However, animals of different sizes or motions at different speeds may not share the same dominant forces within a behavior, making ratios of just two of these forces less useful. Thus, for a broad comparison of behavior across many orders of magnitude of limb length and cycle period, a dimensionless number that includes gravitational, inertial, elastic, and viscous forces is needed. This study proposes a nondimensional number that relates these four forces: the phase shift (ϕ) between the displacement of the limb and the actuator force that moves it. Using allometric scaling laws, ϕ for terrestrial walking is expressed as a function of the limb length and the cycle period at which the limb steps. Scale-dependent values of ϕ are used to explain and predict the electromyographic (EMG) patterns employed by different animals as they walk.

RevDate: 2023-10-11

Saparbayeva N, BV Balakin (2023)

CFD-DEM model of plugging in flow with cohesive particles.

Scientific reports, 13(1):17188.

Plugging in flows with cohesive particles is crucial in many industrial and real-life applications such as hemodynamics, water distribution, and petroleum flow assurance. Although probabilistic models for plugging risk estimation are presented in the literature, multiple details of the process remain unclear. In this paper, we present a CFD-DEM model of plugging validated against several experimental benchmarks. Using the simulations, we consider the process of plugging in a slurry of ice in decane, focusing on inter-particle collisions and plugging dynamics. We conduct a parametric study altering the Reynolds number (3000...9000), particle concentration (1.6...7.3%), and surface energy (21...541 mJ/m[Formula: see text]). We note the process possesses complex non-linear behaviour for the cases where particle-wall adhesion reduces by more than 20% relative to inter-particle cohesion. Finally, we demonstrate how the simulation results match the flow maps based on the third-party experiments.

RevDate: 2023-10-09

Sun T, Liu H, Yan T, et al (2023)

Numerical Study on Enhanced Heat Transfer of Downhole Slotted-Type Heaters for In Situ Oil Shale Exploitation.

ACS omega, 8(39):36043-36052.

In order to improve the flow state of the heater shell side and enhance the performance evaluation of the heater, this paper proposes a perforated plate-type heater model. Based on Fluent, numerical studies are conducted on the heat transfer performance and shell-side fluid flow characteristics of a perforated plate-type heater. The variations of the heat transfer factor Nu, friction factor f, and evaluation parameter Nu/f[1/3] are analyzed for different helix angles β and ratios of the long and short semiaxes of the circular holes on the heating plate under different Reynolds numbers Re. The results reveal that under the same shell-side Reynolds number Re, the heat transfer factor Nu shows an increasing trend with the increase in the proportion of the helix angle β. The heat transfer factor Nu for the heating plate with the hole shape ratio a/b = 1 does not exhibit significant improvement compared to hole shape ratios a/b = 0.8 and a/b = 0.6, but it increases by 4.87 to 7.07% compared to the hole shape ratio a/b = 0.4 in the perforated plate-type heater. On the other hand, the friction factor f decreases as the helix angle β and the ratio of hole shapes on the heating plate increase. The lowest friction factor f is observed for the helix angle β of 25° and the hole shape ratio a/b = 1 in the perforated plate-type heater. When the helix angle β is 25° and the hole shape ratio is a/b = 1, the evaluation parameter Nu/f[1/3] reaches its highest value, indicating the optimal overall performance of the perforated plate-type heater.

RevDate: 2023-10-09

Hosseinzadeh K, Roshani M, Attar MA, et al (2023)

Heat transfer study and optimization of nanofluid triangular cavity with a pentagonal barrier by finite element approach and RSM.

Heliyon, 9(9):e20193.

Nowadays, several engineering applications and academic investigations have demonstrated the significance of heat transfers in general and mixed convection heat transfer (MCHT) in particular in cavities containing obstacles. This study's main goal is to analyze the MCHT of a nanofluid in a triangular cavity with a pentagonal barrier using magneto hydrodynamics (MHD). The cavity's-oriented walls are continuous cold temperature, whereas the bottom wall of the triangle and all pentagonal obstacle walls are kept at a constant high temperature. For solving governing equations, we utilized the Galerkin's finite element approach. Four dimensionless factors, Richardson number (0.01 ≤ Ri ≤ 5), Reynolds number (10 ≤ Re ≤ 50), Buoyancy ratio (0.01 ≤ Br ≤ 10) and Hartmann number (0 ≤ Ha ≤20) are examined for their effects on streamlines, isotherms, concentration, velocity, and the Nusselt number. Also, with the help of Taguchi method and Response Surface Method (RSM) the optimization of the studied dimensionless parameters has been done. The optimum values of Ri, Re, Ha and Br are obtained 4.95, 30.49,18.35 and 0.05 respectively. Ultimately, a correlation has been extracted for obtaining the optimum average Nusselt number (Nu) in mentioned cavity.

RevDate: 2023-10-09

Rasul MG, Ahmed S, Sattar MA, et al (2023)

Hydrodynamic performance assessment of photocatalytic reactor with baffles and roughness in the flow path: A modelling approach with experimental validation.

Heliyon, 9(9):e19623.

Purification of wastewater is essential for human being as well as for the flora and fauna, and sustainable environment. Photocatalytic reactor with TiO2 coated layer can be used to degrade the pollutants but without proper pollutant mass transfer in the reactive surface, photocatalytic reactor decreases its effectiveness. The baffles and rough surface in the flow path can improve the fluid mixing to enhance pollutant mass transfer to improve the reactor's performance. In this study, a computational fluid dynamics (CFD) model has been developed to investigate the effect of four top baffles and three rough surfaces (semi-circular, triangle, and rectangle) on pressure drops, mass transfer and the hydrodynamic performance of the reactor. The experimental investigation was carried out using Formic Acid (FA) as pollutant in feed water for model validation. The simulated result varies only within 5% with the experimental data of FA concentration versus feed flow rate and fluid velocity. The model was run at fluid velocity of 0.15 m/s and 0.5 m/s (Reynolds number of 2150 (laminar flow) and 7500 (turbulent flow), respectively. The simulation result shows that the addition of baffles and roughness on the reactive surfaces increases the turbulent kinetic energy (minimum increase 8%) and consequently increases the mass transfer (maximum increase 37%) of the pollutant. The highest wall shear was observed to be 40 Pa when both square and triangular elements were used as roughness elements at turbulent flow condition. The results also shows that the highest pressure-drop of 8 kPa was found when the square roughness element was used at turbulent flow condition. Overall, the photocatalytic reactor performance is significantly enhanced by the application of combined baffles and roughness elements in the reactive surface.

RevDate: 2023-10-08

Allehiany FM, Memon AA, Memon MA, et al (2023)

Maximizing electrical output and reducing heat-related losses in photovoltaic thermal systems with a thorough examination of flow channel integration and nanofluid cooling.

Scientific reports, 13(1):16961.

In recent years, global energy demand has surged, emphasizing the need for nations to enhance energy resources. The photovoltaic thermal (PV/T) system, capable of generating electrical energy from sunlight, is a promising renewable energy solution. However, it faces the challenge of overheating, which reduces efficiency. To address this, we introduce a flow channel within the PV/T system, allowing coolant circulation to improve electrical efficiency. Within this study, we explore into the workings of a PV/T system configuration, featuring a polycrystalline silicon panel atop a copper absorber panel. This innovative setup incorporates a rectangular flow channel, enhanced with a centrally positioned rotating circular cylinder, designed to augment flow velocity. This arrangement presents a forced convection scenario, where heat transfer primarily occurs through conduction in the uppermost two layers, while the flow channel beneath experiences forced convection. To capture this complex phenomenon, we accurately address the two-dimensional Navier-Stokes and energy equations, employing simulations conducted via COMSOL 6.0 software, renowned for its utilization of the finite element method. To optimize heat dissipation and efficiency, we introduce a hybrid nanofluid comprised of titanium oxide and silver nanoparticles dispersed in water, circulating through the flow channel. Various critical parameters come under scrutiny, including the Reynolds number, explored across the range of 100-1000, the volume fractions of both nanoparticle types, systematically tested within the range of 0.001-0.05, and the controlled speed of the circular cylinder, maintained within the range of 0.1-0.25 m/s. It was found that incorporating silver nanoparticles as a suspended component is more effective in enhancing PV/T efficiency than the addition of titanium oxide. Additionally, maintaining the volume fraction of titanium oxide between 4 and 5% yields improved efficiency, provided that the cylinder rotates at a higher speed. It was observed that cell efficiency can be regulated by adjusting four parameters, such as the Reynolds number, cylinder rotation speed, and the volume fraction of both nanoparticles.

RevDate: 2023-10-05

Zhang B, Liu G, Li Y, et al (2023)

Experimental study on the seepage mutation of natural karst collapse pillar (KCP) fillings over mass outflow.

Environmental science and pollution research international [Epub ahead of print].

Conduction between the unique geological formation karst collapse pillar (KCP) and the fractures caused by mining in the coal seam floor can lead to catastrophic water inrush disasters in many coalmines in Northern China. It is widely recognized that seepage mutation induced by the migration/loss of KCP fillings (highly broken rocks filling the fractured rocks) happens during occurrence of the KCP-related water inrush. However, roles of fluid path (mining-induced fracture) scale and KCP filling porosity in seepage mutation evolution remain unclear. Here, we conducted seepage tests on natural KCP fillings containing rock particles of different sizes. The filling specimens were deformed to different porosities from 14 to 26% through axial compression, and small to large fluid paths were simulated by seepage plates with distinct pore sizes from 2.5 to 12.5 mm. We found that seepage mutation occurs with significant permeability enhancement by 2 orders of magnitude under a pore diameter of 12.5 mm and a specimen porosity of 26%. There is a strong linear relationship between specimen permeability and Reynolds number (Re) over seepage mutation. The mutation is caused by the sudden collapse of the specimen skeleton and subsequent quick outflow of the particles. Therefore, it is inferred that the KCP-related water inrush is more likely to happen when highly porous KCP fillings are present and mining-induced fractures are well developed.

RevDate: 2023-10-03

Duraes ADS, JD Gezelter (2023)

A theory of pitch for the hydrodynamic properties of molecules, helices, and achiral swimmers at low Reynolds number.

The Journal of chemical physics, 159(13):.

We present a theory for pitch, a matrix property that is linked to the coupling of rotational and translational motion of rigid bodies at low Reynolds numbers. The pitch matrix is a geometric property of objects in contact with a surrounding fluid, and it can be decomposed into three principal axes of pitch and their associated moments of pitch. The moments of pitch predict the translational motion in a direction parallel to each pitch axis when the object is rotated around that axis and can be used to explain translational drift, particularly for rotating helices. We also provide a symmetrized boundary element model for blocks of the resistance tensor, allowing calculation of the pitch matrix for arbitrary rigid bodies. We analyze a range of chiral objects, including chiral molecules and helices. Chiral objects with a Cn symmetry axis with n > 2 show additional symmetries in their pitch matrices. We also show that some achiral objects have non-vanishing pitch matrices, and we use this result to explain recent observations of achiral microswimmers. We also discuss the small but non-zero pitch of Lord Kelvin's isotropic helicoid.

RevDate: 2023-09-29

Zhu Q (2023)

Locomotion performance of an axisymmetric 'flapping fin'.

Bioinspiration & biomimetics [Epub ahead of print].

Inspired by the jet-propulsion mechanism of aquatic creatures such as sea salps, a novel locomotion system based on an axisymmetric body design is proposed. This system consists of an empty tube with two ends open. When the diameters of the front and back openings are changed periodically, the forward-backward symmetry is broken so that the system starts swimming. Viewed within a cross section, this system resembles a two-dimensional flapping fin with its leading edge located at the front opening and the trailing edge at the back opening. The feasibility of this system has been proven via numerical simulations using a fluid-structure interaction model based on the immersed-boundary framework. According to the results, at relatively low Reynolds number (O(100)), this simple locomotion method can easily achieve a mean swimming speed of 2 to 3 body lengthes per deformation period. Further simulations illustrate the following characteristics: 1) Within the chamber, the hydrodynamic interactions among different parts of the body leads to a performance-enhancing mechanism similar to the ground effect; 2) Reducing the diameter of the body can strengthen this effect so that both the swimming speed and the energy efficiency are improved; 3) For better performance the amplitude of diameter oscillation at the trailing edge should be larger or at least equal to the one at the leading edge. .

RevDate: 2023-09-28

Juraeva M, DJ Kang (2023)

Design and Mixing Analysis of a Passive Micromixer Based on Curly Baffles.

Micromachines, 14(9): pii:mi14091795.

A novel passive micromixer based on curly baffles is proposed and optimized through the signal-to-noise analysis of various design parameters. The mixing performance of the proposed design was evaluated across a wide Reynolds number range, from 0.1 to 80. Through the analysis, the most influential parameter was identified, and its value was found to be constant regardless of the mixing mechanism. The optimized design, refined using the signal-to-noise analysis, demonstrated a significant enhancement of mixing performance, particularly in the low Reynolds number range (Re< 10). The design set obtained at the diffusion dominance range shows the highest degree of mixing (DOM) in the low Reynolds number range of Re< 10, while the design set optimized for the convection dominance range exhibited the least pressure drop across the entire Reynolds number spectrum (Re< 80). The present design approach proved to be a practical tool for identifying the most influential design parameter and achieving excellent mixing and pressure drop characteristics. The enhancement is mainly due to the curvature of the most influential design parameter.

RevDate: 2023-09-27

Jafari E, Malayeri MR, Brückner H, et al (2023)

Innovative spiral electrode configuration for enhancement of electrocoagulation-flotation.

Journal of environmental management, 347:119085 pii:S0301-4797(23)01873-X [Epub ahead of print].

The performance of electrocoagulation-flotation (ECF) process can profoundly be affected by the reactor design and electrode configuration. These may, in turn, influence the removal efficiency, flow hydrodynamic, floc formation, and flotation/settling characteristics. The present work aimed at developing a new spiral electrode configuration to enhance the ECF process. To do so, the impacts of parameters such as energy consumption, removal efficiency of the contaminants from industrial wastewater with a composition of turbidity, emulsified oil, and heavy metals (Si, Zn, Pb, Ni, Cu, Cr, and Cd), as well as stirring speed and foaming have been investigated. Comparison was also made between the experimental results of the new electrode configuration with the conventional rectangular cell with plate electrode configuration with the same volume and electrode surface area. The findings revealed that energy consumption of the spiral electrode configuration within the operating times of 10, 20, 30, 32, 48, and 70 min, was approximately 20% lower compared to that of the conventional ECF. Moreover, the maximum and minimum removal efficiency of 97% and 60% were obtained for turbidity and TOC for the stirring speed of 500 rpm and Reynolds number of 10,035, respectively. Finally, the formed gas bubbles tilted toward the center due to the enhanced flow hydrodynamic which resulted in substantial reduction of foam formation.

RevDate: 2023-09-27

Rajendran S, Jog MA, RM Manglik (2023)

Predicting the Splash of a Drop Impacting a Thin Liquid Film.

Langmuir : the ACS journal of surfaces and colloids [Epub ahead of print].

An experimental study is carried out to investigate droplet-film interactions when a drop impinges on a thin stagnant film of the same liquid. The impacting drop causes either liquid deposition or splash, consisting of prompt generation of secondary drops or a delayed process. By varying the drop diameter and impact velocity, measurements are made to characterize the phenomena using five different liquids that are chosen to cover a wide range of liquid properties (viscosity and surface tension). The drop impact dynamics are captured with a high-speed digital camera with real-time, high-resolution image processing. The drop-splash threshold is found to scale with inertial and viscous forces, or Reynolds number (Re), as well as capillary forces, as described by the balance of gravitational and interfacial tension forces, or Bond number (Bo); fluid properties are described by their Morton number (Mo). A correlation, functionally expressed as Re = ϕ(Bo,Mo), is devised to determine the splash/no-splash (or deposition) boundary, and the predictions for the splash/no-splash outcomes agree well with the experimental outcomes as well as those readily available in the literature.

RevDate: 2023-09-27

Hickey DJ, Golestanian R, A Vilfan (2023)

Nonreciprocal interactions give rise to fast cilium synchronization in finite systems.

Proceedings of the National Academy of Sciences of the United States of America, 120(40):e2307279120.

Motile cilia beat in an asymmetric fashion in order to propel the surrounding fluid. When many cilia are located on a surface, their beating can synchronize such that their phases form metachronal waves. Here, we computationally study a model where each cilium is represented as a spherical particle, moving along a tilted trajectory with a position-dependent active driving force and a position-dependent internal drag coefficient. The model thus takes into account all the essential broken symmetries of the ciliary beat. We show that taking into account the near-field hydrodynamic interactions, the effective coupling between cilia even over an entire beating cycle can become nonreciprocal: The phase of a cilium is more strongly affected by an adjacent cilium on one side than by a cilium at the same distance in the opposite direction. As a result, synchronization starts from a seed at the edge of a group of cilia and propagates rapidly across the system, leading to a synchronization time that scales proportionally to the linear dimension of the system. We show that a ciliary carpet is characterized by three different velocities: the velocity of fluid transport, the phase velocity of metachronal waves, and the group velocity of order propagation. Unlike in systems with reciprocal coupling, boundary effects are not detrimental for synchronization, but rather enable the formation of the initial seed.

RevDate: 2023-09-25

Younis O, Abderrahmane A, Hatami M, et al (2023)

Nanoencapsulated phase change material in a trapezoidal prism wall under the magnetic field effect for energy storage purposes.

Scientific reports, 13(1):16060.

Recently, Nano-encapsulated phase change materials (NEPCM) have attracted the attention of researchers due to their promising application in thermal management. This research investigates magnetohydrodynamic mixed convection of NEPCM contained within a lid-driven trapezoidal prism enclosure containing a hot-centered elliptical obstacle. The upper cavity wall is moving at a constant velocity; both inclined walls are cold, while the rest of the walls are insulated. The Galerkin Finite Element Method was used to solve the system's governing equations. The influence of Reynolds number (Re 1-500), Hartmann number (Ha = 0-100), NEPCM volumetric fraction φ (0-8%), and elliptical obstacle orientation α (0-3π/4) on thermal fields and flow patterns are introduced and analyzed. The results indicated that the maximum heat transfer rate is observed when the hot elliptic obstacle is oriented at 90°; an increment of 6% in the Nu number is obtained in this orientation compared to other orientations. Reducing Ha from 100 to 0 increased Nu by 14%. The Maximum value of the Bejan number was observed for the case of Ha = 0, α = 90° and φ = 0.08.

RevDate: 2023-09-25

Abd-Alla AM, Abo-Dahab SM, Abdelhafez MA, et al (2023)

Effect of heat and mass transfer on the nanofluid of peristaltic flow in a ciliated tube.

Scientific reports, 13(1):16008.

The current work focuses attention on discussing the peristaltic flow of Rabinowitsch nanofluid through ciliated tube. This technical study analyzes heat and mass transfer effects on the flow of a peristaltic flow, incompressible, nanofluid via a ciliated tube. The governing non-linear partial differential equations representing the flow model are transmuted into linear ones by employing the appropriate non-dimensional parameters under the assumption of long wavelength and low Reynolds number. The flow is examined in wave frame of reference moving with the velocity [Formula: see text]. The governing equations have been solved to determine velocity, temperature, concentration, the pressure gradient, pressure rise and the friction force. Using MATLAB R2023a software, a parametric analysis is performed, and the resulting data is represented graphically. The results indicate that the various emerging parameters of interest significantly affect the nanofluid properties within the tube. The present study enhances the comprehension of nanofluid dynamics in tube and offers valuable insights into the influence of heat and mass transfer in such setups. Convective heat transfer is found to be greater at the boundaries resulting in decreased temperature there.

RevDate: 2023-09-25

Abbas N, Shatanawi W, Hasan F, et al (2023)

Thermodynamic flow of radiative induced magneto modified Maxwell Sutterby fluid model at stretching sheet/cylinder.

Scientific reports, 13(1):16002.

A steady flow of Maxwell Sutterby fluid is considered over a stretchable cylinder. The magnetic Reynolds number is considered very high and induced magnetic and electric fields are applied on the fluid flow. Joule heating and radiation impacts are studied under the temperature-dependent properties of the liquid. Having the above assumptions, the mathematical model has been evolving via differential equations. The differential equations are renovated in the dimensionless form of ordinary differential equations using the appropriate transformations. The numerical results have been developed employing numerical techniques on the ordinary differential equations. The impact of involving physical factors on velocity, induced magneto hydrodynamic, and temperature function is debated in graphical and tabular form. The velocity profile is boosted by thicker momentum boundary layers, which are caused by higher values of the magnetic field factor. So, the fluid flow becomes higher velocity due to enlarging values of the magnetic field factor. Heat transfer factor and friction at surface factor boosted up for increment of [Formula: see text] (Magnetic field factor). The [Formula: see text](Magnetic field factor) is larger which better-quality of heat transfer at surface and also offered the results of friction factor boosting up in both cases of stretching sheet/cylinder. The [Formula: see text](Magnetic Prandtl number) increased which provided better-quality of heat transfer at surface.

RevDate: 2023-09-23

Wang Z, M Sedighi (2023)

Dispersion properties of nanoplastic spheres in granular media at low Reynolds numbers.

Journal of contaminant hydrology, 259:104244 pii:S0169-7722(23)00114-6 [Epub ahead of print].

Nanoplastic particles (<1 μm) are among the contaminants of emerging concern, and compared to microplastic (<5 mm), our understanding of the transport and fate of nanoplastic in water, sediments and soil is very limited. This paper focuses on developing fundamental insight into the dispersion behaviour (sum of hydrodynamic dispersion and diffusion) of nanoplastic spheres, which are likely the most mobile shape of nanoplastic. We measured the dispersion coefficient and dispersivity of nanoplastic spheres (100 nm, 300 nm and 1000 nm diameter) in granular media with a range of pore sizes. We investigated the mechanisms that control the behaviour at low Reynolds number (smaller than 2), relevant to the dispersion of nanoplastic across the riparian area at water velocities of the common river and shallow groundwater. The measured dispersion coefficients were compared with the predictions by two commonly used models. The results show that there are significant differences between measurements and predictions for the case of colloidal size nanoplastics (MAPE>100%). The retarded dispersion caused by the size-exclusion effect was observed to be important in the case of 1.7 mm and 0.4 mm granular media for 300 nm and 1000 nm nanoplastics, reducing the dispersivity and sensitivity to Reynolds number. The methodology in this paper can be adopted in studies on other sizes and shapes of nanoplastic, assisting with predicting the transport and fate of nanoplastic granular media.

RevDate: 2023-09-19

Mamori H, Nabae Y, Fukuda S, et al (2023)

Dynamic state of low-Reynolds-number turbulent channel flow.

Physical review. E, 108(2-2):025105.

We numerically study the dynamic state of a low-Reynolds-number turbulent channel flow from the viewpoints of symbolic dynamics and nonlinear forecasting. A low-dimensionally (high-dimensionally) chaotic state of the streamwise velocity fluctuations emerges at a viscous sublayer (logarithmic layer). The possible presence of the chaotic states is clearly identified by orbital instability-based nonlinear forecasting and ordinal partition transition network entropy in combination with the surrogate data method.

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In the early 1990's, Robert Robbins was a faculty member at Johns Hopkins, where he directed the informatics core of GDB — the human gene-mapping database of the international human genome project. To share papers with colleagues around the world, he set up a small paper-sharing section on his personal web page. This small project evolved into The Electronic Scholarly Publishing Project.

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