Tangential Fluid Research Articles

Mixture Theory-Based Finite Element Approach for Analyzing the Edematous Condition of Biological Soft Tissues.

In hydrated soft biological tissues experiencing edema, which is typically associated with various disorders, excessive fluid accumulates and is encapsulated by impermeable membranes. In certain cases of edema, an indentation induced by pressure persists even after the load is removed. The depth and duration of this indentation are used to assess the treatment response. This study presents a mixture theory-based approach to analyzing the edematous condition. The finite element analysis formulation was grounded in mixture theory, with the solid displacement, pore water pressure, and fluid relative velocity as the unknown variables. To ensure tangential fluid flow at the surface of tissues with complex shapes, we transformed the coordinates of the fluid velocity vector at each time step and node, allowing for the incorporation of the transmembrane component of fluid flow as a Dirichlet boundary condition. Using this proposed method, we successfully replicated the distinct behavior of pitting edema, which is characterized by a prolonged recovery time from indentation. Consequently, the proposed method offers valuable insights into the finite element analysis of the edematous condition in biological tissues.

Analysis of electromagnetic and radiative heat source on tangential hyperbolic fluid under Arrhenius kinetic with convective cooling

The global threat of environmental degradation from harmful waste discharge is evident, leading to unusual diseases and natural disasters. Some of these toxic emissions result from human activities, such as the incomplete combustion of hydrocarbons. As such, this study aims to explore the analysis of electromagnetic and radiative heat sources on tangential hyperbolic fluid under Arrhenius kinetic with convective cooling. The transformed momentum and heat equations are solved using a rigorous computational approach called the Galerkin integration approximation with weighted residual method. This computational methodology ensures the reliability and accuracy of the results. Various graphs illustrate the results, showing parametric sensitivity profiles for the velocity, temperature, skin friction, thermal gradient, Bejan, and entropy generation. As noticed from the outcomes, electric field loading increases heat dispersion by about 3.25 % as heat source terms are enhanced. Increasing magnetic field, radiation, and electric field loading parameters strengthened thermodynamic equilibrium and minimized entropy generation. The tangential hyperbolic combustion process is 6.11 % increased with rising Brinkman number and electric field loading terms. The flow rate and temperature field are increased to the peak along the middle of the channel for increasing pressure gradient.

Thermal dissipation of two-step combustible tangent hyperbolic fluid with quadratic Boussinesq approximation and convective cooling

This study explores thermal criticality and dissipation involving a two-step reaction in a hyperbolic tangential fluid flow and quadratic Boussinesq approximation to model the complex internal heat transfer mechanisms during combustion. Subject to suitable convective boundary conditions, the transformed energy and momentum equations are numerically solved using Galerkin approximation integration coupled with a weighted residual scheme. The outcomes are disseminated using a variety of graphs to illustrate for parametric sensitivities of the thermal and velocity profiles. Based on the results, it is discovered that increases in the Frank-Kamenetskii parameter, Brinkman number, Weissenberg number, activation energy, activation ratio term, and second step term all aid in the complete combustion of hydrocarbons. Monitoring all terms that stimulate internal heat generation is essential to avoid system blow-ups.

Influence of impeller clearance, impeller size and baffles on copper sorption on zeolite NaX: Do the size and position really matter?

Even though optimal mixing parameters may significantly influence the sorption process and its costs, the influence of hydrodynamics on sorption in a batch reactor hasn't yet been adequately studied. In this study, the hydrodynamic conditions produced by pitched blade turbine (PBT) impellers of various diameters and positions in baffled and unbaffled reactors were investigated. The objective was to investigate their influence on the just suspended impeller speed (NJS), power consumption per zeolite mass and the sorption process at the same temperature, initial copper solution concentration, and zeolite particle size in all the experiments conducted. The results show that NJS generally decreases as impeller diameter increases and is lower in the reactor without baffles. A transient multiphase computational fluid dynamics model was developed to provide valuable insight into the complex flow kinetics and it was found that the further the impeller is from the bottom of the baffled reactor the wider is the secondary suspension flow and the intensity of the flow below the impeller decreases. For this reason, complete suspension of the NaX zeolite particles in the solution was achieved at a higher PBT impeller speed. Due to the swirling motion of the suspension, this phenomenon is not observed in the unbaffled reactor for all the impellers used besides the smallest one. The power consumption per zeolite mass, at the state of complete zeolite suspension, increases in baffled reactor and decreases in unbaffled reactor with increasing impeller diameter having significantly lower values in the unbaffled reactor. The significantly lower power consumption per zeolite mass in an unbaffled system could be attributed to, not only the generally lower NJS values, but also to the resistance force which baffles make to the tangential fluid flow. The Ritchie model and Mixed surface reaction and diffusion controlled adsorption kinetic model were used for the kinetic analysis of the experimental kinetic data. The kinetic results indicate that the process is faster when the impeller is at the standard of bottom clearance, regardless of the presence of the baffles.

Unsteady squeezing Casson fluid through rotating discs under the variable magnetic field, cross diffusion and chemical reaction effects

There are several industrial and biological applications for the study of squeezing flow, including cell squeeze technology, blood flow and food production. In particular, the load and thrust bearing qualities of human body joints and the compression molding processes of metals and polymers might be explained by this solution, which could also illustrate the classical lubrication problems. So, this work investigated the effects of cross-diffusion, an induced magnetic field and joule heating on an unsteady squeezing Casson fluid on a spinning disc. Using the proper similarity transformations, the systems of partial differential equations are drained into a system of ordinary differential equations, which are solved numerically using the finite difference method. This analysis accounts for the effects of biophysical parameters on velocity components, magnetic fields, heat and mass transfer profiles. Additionally, graphic representations are provided for the skin friction coefficient, Nusselt number and Sherwood number for various values of the governing parameters. The current investigation has been matched with published results in order to validate validity, and good agreements have been seen. The impacts of the problem parameters under consideration are also explained numerically and graphically. The top disc’s rate of rotation is found to enhance the tangential fluid flow and temperature distribution, while it reduces velocity in the other directions and the induced magnetic field.

Stokes flow solutions in infinite and semi‐infinite porous channels

AbstractWe derive a class of exact solutions for Stokes flow in infinite and semi‐infinite channel geometries with permeable walls. These simple, explicit, series expressions for both pressure and Stokes flow are valid for all permeability values. At the channel walls, we impose a no‐slip condition for the tangential fluid velocity and a condition based on Darcy's law for the normal fluid velocity. Fluid flow across the channel boundaries is driven by the pressure drop between the channel interior and exterior; we assume the exterior pressure to be constant. We show how the ground state is an exact solution in the infinite channel case. For the semi‐infinite channel domain, the ground‐state solutions approximate well the full exact solution in the bulk and we derive a method to improve their accuracy at the transverse wall. This study is motivated by the need to quantitatively understand the detailed fluid dynamics applicable in a variety of engineering applications including membrane‐based water purification, heat and mass transfer, and fuel cells.

Numerical Analysis of the Erosion Mechanism inside the Tube Sockets of Main Steam Thermometers in a Coal-Fired Power Plant

Leakage occurring in the tube sockets of the main steam thermometers can seriously threaten the safe operation of coal-fired power plants. Here, assuming a 300 MW unit as a relevant testbed, this problem is investigated numerically through solution of the equations of fluid-dynamics in synergy with the mathematical treatment of relevant statistics. The results indicate that the steam can form a large-scale spiral flow inside the tube socket and continuously scour the inner wall. In the model with the protective casing setting angle of 60°, the average tangential fluid velocity can reach up to 4.8 m/s, which is about twice higher than that in the model with the protective casing setting angle of 0°. The wake disturbance generated by the flow around the thermo-sensitive body leads to differences in the fluid motion inside the tube sockets between the upstream and downstream thermometers. These differences are affected by the distance between the thermometers, the setting angle of protective casing, and other factors. The pressure of the main steam inside the tube socket for a R3 thermometer, located outside the curved pipeline, is about 1756 Pa higher than that of the L3 thermometer located outside the straight pipeline, indicating that the secondary flow generated in the curved pipeline is able to provide stronger energy for the large-scale spiral flow inside the tube socket. On the basis of these findings, an improvement scheme for the installation of longitudinal ribs in the tube sockets is proposed. The simulation results show that the average tangential velocity of the fluid within the near-wall area of tube sockets decreases by more than 90%, which should be enough to effectively alleviate the damage to the inner wall caused by high-pressure fluid or particles.

Impact of Fluid Dynamics on the Viability and Differentiation Capacity of 3D-Cultured Jaw Periosteal Cells

Perfused bioreactor systems are considered to be a promising approach for the 3D culturing of stem cells by improving the quality of the tissue-engineered grafts in terms of better cell proliferation and deeper penetration of used scaffold materials. Our study aims to establish an optimal perfusion culture system for jaw periosteal cell (JPC)-seeded scaffolds. For this purpose, we used beta-tricalcium phosphate (β-TCP) scaffolds as a three-dimensional structure for cell growth and osteogenic differentiation. Experimental set-ups of tangential and sigmoidal fluid configurations with medium flow rates of 100 and 200 µL/min were applied within the perfusion system. Cell metabolic activities of 3D-cultured JPCs under dynamic conditions with flow rates of 100 and 200 µL/min were increased in the tendency after 1, and 3 days of culture, and were significantly increased after 5 days. Significantly higher cell densities were detected under the four perfused conditions compared to the static condition at day 5. However, cell metabolic and proliferation activity under dynamic conditions showed flow rate independency in our study. In this study, dynamic conditions increased the expression of osteogenic markers (ALPL, COL1A1, RUNX2, and OCN) compared to static conditions and the tangential configuration showed a stronger osteogenic effect than the sigmoidal flow configuration.

Mechanistic determination of tear film thinning via fitting simplified models to tear breakup

Purpose: Little quantitative or mechanistic information about tear film breakup can be determined directly via current imaging techniques. In this paper, we present simplified mathematical models based on two proposed mechanisms of tear film breakup: evaporation of water from the tear film and tangential fluid flow within the tear film. We use our models to determine whether one or a combination of the two mechanisms causes tear film breakup in a variety of instances. In this study, we estimate related breakup parameters that cannot currently be measured in breakup during subject trials, such as tear film osmolarity and thinning rates. The present study validates our procedure against previous work.Methods: Five ordinary differential equation models for tear film thinning were designed that model evaporation, osmosis, and various types of tangential flow. Eight tear film breakup instances occurring within a time interval of 1–8 s postblink of five healthy subjects thatwere identified in fluorescence images in previous work were fit with these five models. The fitting procedure used a nonlinear least squares optimization that minimized the difference of the computed theoretical fluorescent intensity from the models and the experimental fluorescent intensity from the images. The optimization was conducted over the evaporation rate and up to three tangential flow rate parameters. The smallest norm of the difference was determined to correspond to the model that best explained the tear film dynamics.Results: All of the breakup instances were best fit by models with time-dependent tangential flow. Our optimal parameter values and thinning rate as well as tangential fluid flow profiles compare well with previous partial differential equation model results in most instances.Conclusion: Our fitting results suggest that a combination of tangential fluid flow and evaporation cause most of the breakup instances. Comparison with results from previous work suggests that the simplified models can capture the essential tear film dynamics in most cases, thereby validating this procedure for wider usage.

Entropy optimized Darcy‐Forchheimer slip flow of Fe3O4−CH2OH2 nanofluid past a stretching/shrinking rotating disk

AbstractFerrofluids are made out of nanoscale ferromagnetic particles and known as colloidal liquids suspended on a bearer liquid, normally water (H2O) or an organic solvent like kerosene. Ferrofluid is utilized in rotary seals, computer hard drives, loudspeakers, magnetic resonance imaging, and so forth. The present article reveals the extent of effectiveness available from the investigation on entropy generation, thermal radiation, viscous dissipation on Darcy‐Forchheimer convective slip flow of nanofluid (nf) past stretching/shrinking rotating disk (RD) subject to suction. The concepts of different parameters and their effects on velocity, temperature, entropy generation number, and Bejan number profiles have been elaborated in this explanatory paper. The explanations using graphs and numerical tables help smoothen the understanding and strengthen the interpretations of the results of the study. The major eye‐catching outcome of the study is that the augmented slip parameter undermines the tangential velocity and fluid suction invites a diminutive radial velocity as well as temperature distribution due to stretching/shrinking RD. Enhanced Reynolds number peters out the entropy generation number for stretching RD, which was the goal of the study to be accomplished.

DNA Capture by Nanopore Sensors under Flow.

Integrating nanopore sensors within microfluidic architectures is key to providing advanced sample processing capabilities upstream of the biosensor. When confined in a microchannel, the nanopore capture and translocation characteristics are altered when subjected to cross-flow, affecting sensor performance. Here, we study the capture rate and translocation of 1-5 kbp double-stranded DNA molecules through solid-state nanopores in the presence of tangential fluid flow over the nanopore aperture. Experiments reveal a trend of increased capture rate with cross-flow, reaching a 5-fold enhancement (dependent on DNA length) at moderate flow rates, before decreasing at higher flow rates. By modeling DNA dynamics in microchannels under the combined effect of laminar flow, Brownian motion and electrophoretic drift, it is shown that the observed trend is the result of two competing mechanisms: enhanced DNA transport by convection and reduction in the nanopore's capture volume with increased flow velocity. Moreover, it is shown that the viscous drag force exerted by flow on a translocating DNA can be exploited to tune the kinetics of DNA translocation.

A New Mathematical Model for the Prediction of Internal Recirculation in Impinging Streams Reactors

A mathematical model for the prediction of internal recirculation of complex impinging stream reactors has been presented. The model constitutes a repetition of a series of ideal plug flow reactors and CSTR reactors with recirculation. The simplicity of the repeating motif allows for the derivation of an algebraic relation of the whole system using the Laplace transform. An impinging streams reactor system with one axial and two tangential inlet fluid streams was constructed and considered as a case study. The model predicts satisfactorily the complex and flow rate dependent experimental residence time distribution functions obtained employing a pulse tracer method for different total flow rates of the incoming feed. The variation of the controlling parameters with changing the total inlet flow rate is discussed. The presented model can predict complex internal recirculation streams within the impinging streams reactor system.

Freeze-Dried Extracellular Vesicles From Adipose-Derived Stem Cells Prevent Hypoxia-Induced Muscle Cell Injury.

Cellular therapies have tremendous potential for the successful treatment of major extremity wounds in the combat setting, however, the challenges associated with transplanting stem cells in the prolonged field care (PFC) environment are a critical barrier to progress in treating such injuries. These challenges include not only production and storage but also transport and handling issues. Our goal is to develop a new strategy utilizing extracellular vesicles (EVs) secreted by stem cells that can resolve many of these issues and prevent ischemic tissue injury. While EVs can be preserved by freezing or lyophilization, both processes result in decrease in their bioactivity. Here, we describe optimized procedures for EVs production, isolation, and lyophilization from primary human adipose-derived stem cells (hADSCs). We compared two isolation approaches that were ultrafiltration (UF) using a tangential fluid filtration (TFF) system and differential ultracentrifugation (UC). We also optimized EVs lyophilization in conjunction with trehalose and polyvinylpyrrolidone 40 (PVP40) as lyoprotectants. Bioactivity of EVs was assessed based on reversal of hypoxia-induced muscle cell injury. To this end, primary human myoblasts were subjected to hypoxic conditions for 6 h, and then treated with hADSC-derived EVs at a concentration of 50 μg/mL. Subsequently, muscle cell viability and toxicity were evaluated using MTS and LDH assays, respectively. Overall, nanoparticle tracking data indicated that UF/TFF yields threefold more particles than UC. Lyophilization of EVs resulted in a significantly reduced number of particles, which could be attenuated by adding lyoprotections to the freeze-drying solution. Furthermore, EVs isolated by UF/TFF and freeze-dried in the presence of trehalose significantly increased viability (P < 0.0193). Taken together, our findings suggest that the isolation and preservation methods presented in this study may enhance therapeutic applications of EVs.

A variational formulation for steady surface water waves on a Beltrami flow

This paper considers steady surface waves ‘riding’ a Beltrami flow (a three-dimensional flow with parallel velocity and vorticity fields). It is demonstrated that the hydrodynamic problem can be formulated as two equations for two scalar functions of the horizontal spatial coordinates, namely the elevation η of the free surface and the potential Φ defining the gradient part (in the sense of the Hodge–Weyl decomposition) of the horizontal component of the tangential fluid velocity there. These equations are written in terms of a non-local operator H ( η ) mapping Φ to the normal fluid velocity at the free surface, and are shown to arise from a variational principle. In the irrotational limit, the equations reduce to the Zakharov–Craig–Sulem formulation of the classical three-dimensional steady water-wave problem, while H ( η ) reduces to the familiar Dirichlet–Neumann operator.

Alternative Frictional Model for Discontinuous Shear Thickening of Dense Suspensions: Hydrodynamics.

A consensus has emerged that a constraint to rotational or sliding motion of particles in dense suspensions under flow is the genesis of the discontinuous shear thickening (DST) phenomenon. We show that tangential fluid lubrication interactions due to finite-sized asperities on particle surfaces effectively provide these constraints, changing the dynamics of particle motion. By explicitly resolving for the surface roughness of particles, we show that, while smooth particles exhibit continuous shear thickening, purely hydrodynamic interactions in rough particles result in DST. In contrast to the frictional contact model, the hydrodynamic model predicts negative first and second normal stress differences for dense suspensions in the shear thickened state.

Coupling membrane and Fe–Pd bimetallic nanoparticles for trichloroethene removing from water

A novel composite membrane with membrane pores loading acrylic acid microgels coated by Fe–Pd bimetallic nanoparticles (NPs) was prepared for the dechlorination of trichloroethene (TCE) in water. This membrane was prepared by firstly immobilizing acrylic acid microgels in poly (vinylidene fluoride) (PVDF) membrane pores and then in-situ synthesis of Fe–Pd bimetallic nanoparticles (NPs). The Fe–Pd NPs coupled with the porous membranes enabled dechlorination to be conducted in a cross-flow model including a penetrative flow and a tangential flow. In such a model, a large number of dechlorination occurred in penetrative flow fluid while no dechlorination occurred in tangential flow fluid. Thus, products and reactants are always timely isolated in the cross-flow dechlorination process. The composite membrane prevents Fe–Pd NPs from contamination because its nanosize surface pores stop colloids and bovine serum albumin (BSA) from entering into the membrane interior. However, these small surfaces pores cannot slow the diffusion of reactants into membrane pores, and thus make the as-formed composite membrane also show a fast dechlorination rate in a batch reaction. All in all, TCE dechlorination by the composite membrane shows many advantages including the fast dechlorination rate, the convenient operation, the timely isolation of products from reactants, and the ignorable extra steps for separation of metal NPs.

The Fluid Force on a Whirling Columnar Rotor

In the operation of hydro turbines and pump, self-excited vibration can occur due to fluid force which is generated as a response to the vibration and is called rotordynamic fluid force. The tangential component of rotordynamic fluid force has large impact on the stability of rotors. Characteristics of the tangential fluid force acting on a whirling columnar rotor which is modelled on the front shroud of a Francis turbine during self-excited vibration were investigated in computation in the present study. The angular velocity of the whirling motion of the rotor and the tangential force could be normalized by the axial velocity of axial leakage flow through the clearance between the rotor and the casing and the square of it, respectively. In the range of large whirling velocity, the tangential force was caused by a pressure distribution in the case without axial leakage flow. In the range of small whirling velocity, it is known that the tangential force is generated by the inertia of axial leakage flow. In the range of middle whirling velocity, the tangential force was found to be caused by both effects of whirling motion of the rotor in static fluid and the inertia of axial leakage flow. The pressure distribution without axial leakage flow was due to pressure loss in the wake of the rotor in addition to effects of shear stress and discharge from /suction into the clearance.

Hydrodynamics forces on a circular particle near a sinusoidal corrugated wall

We study the hydrodynamic forces acting on a fixed particle close to a corrugated wall experiencing tangential fluid flow, using the lattice Boltzmann method. To carry out a fundamental analysis, a single two-dimensional circular particle near a sinusoidal wall is selected as a case study. The influence of the particle distance from the wall, the particle Reynolds number, corrugation amplitude, and downstream particle position (relative to a corrugation-peak) on the drag, lift and torque acting on the particle are investigated. Our simulations reveal that the hydrodynamic forces change significantly by changing the particle distance from the wall. Even the direction of forces and torque may change, depending on the distance from the wall, downstream particle position and Rep number. We find an increase in magnitude of forces and torque by increasing the corrugation amplitude of the wall.

Hydrodynamics in cavitation device under tangential supply fluid

The design features of the hydrodynamic type cavitation device working section with the input swirling flow are theoretically analyzed. In order to describe such processes was used the flow hydrodynamics modeling performed with the help of numerical methods of the SolidWorks software system and the Flow simulation module. Comparison of results from visual and experimental studies are performed. Visual observations indicate that the life cycle of vapor-gas bubbles and cavities in the design under study can be divided into several periods, in particular the formation of vapor-gas bubbles, their growth, the generation of cavities, volume increase, transformation and destruction. The influence of input and output hydrodynamic and technological parameters of the flow and the design features on the character of the cavitation site and the form of cavitation were studied. According to the results of theoretical and experimental research, rational mode of operation of the cavitation device is proposed. The frequency of oscillations (pulsations) of a cavity is calculated, depending on Reynolds number and Strouhal number. For the dependence Sh = f (Re, P2 / P1), the regression coefficients are calculated, and adequate experimental results with an error of less than 10% are obtained.

Numerical and Experimental Analyses of Dynamic Characteristics for Liquid Annular Seals With Helical Grooves in Seal Stator

Numerical and experimental analyses were carried out to investigate the dynamic characteristics of liquid annular seals with helical grooves in the seal stator. In the numerical analysis, the governing equations were the momentum equations with turbulent coefficients and the continuity equation, all averaged across the film thickness and expressed using an oblique coordinate system in which the directions of coordinate axes coincided with the circumferential direction and the direction along the helical grooves. These governing equations were solved numerically to obtain the dynamic characteristics, such as the dynamic fluid-film forces, dynamic coefficients, and whirl-frequency ratio (WFR). The numerical analysis included the effect of both fluid inertia and energy loss at the steps between the helical groove and the land sections. In the experiments, the dynamic fluid-film pressure distributions, which were induced by a small whirling motion of the rotor about the seal center, were measured to obtain the dynamic characteristics. The equivalent numerical results reasonably agree with the experimental results, demonstrating the validity of the numerical analysis. The value of the tangential dynamic fluid force induced by the rotor whirling motion decreased with increasing the helix angle γ. Consequently, the values of the cross-coupled stiffness coefficient and WFR decreased with increasing γ and became negative for large γ. In general, pump rotors rotate with a forward whirling motion under normal operating conditions. Hence, the negative value of WFR for helically grooved seals contributes to rotor stability by suppressing the forward whirling motion of the rotor.