Fluid Momentum Research Articles

A point particle source model for conjugate heat and mass transfer in dispersed two-phase flows by BEM based methods

The paper reports on development of a Boundary Element Method (BEM) based two phase dispersed flow model, that allows an accurate and efficient heat and mass transfer coupling by using a moving point source model to account for particle–fluid interaction. The two-way coupling model highlights the efficient use of the elliptic fundamental solution and the Dirac delta distribution properties to accurately evaluate the heat and mass point particle source impact on the continuous phase, solved by the Boundary Domain Integral Method (BDIM). In addition to the BDIM model of the particle–fluid heat and mass transfer interaction, the two-phase flow case under consideration is extended to the case of porous spherical particle drying with internal moving drying front, which is solved by the Boundary Element Method. As the two-phase flow is considered to be dilute, the particle–fluid momentum exchange is covered by a one-way coupling algorithm, with Lagrangian particle tracking used for determination of particle positions and velocities in the flow. Two computational cases are presented, where 1000 and 10000 particles are dried in a stream of hot air. Comparison between the obtained drying times for the cases of the one-way and the two-way heat and mass transfer coupling results shows, that the developed two-way coupling model accurately captures the effect of moisture accumulation and temperature decrease in the fluid phase, leading to realistic computations of drying rates of particles in the flow.

Influence of viscoelasticity on ultrasonic propagation in poly(ethylene oxide) aqueous solution

Generally, ultrasonic propagation in ultrasonic non-destructive testing is regarded as a linear process, during which the interaction between ultrasonic and measured material is rarely considered. In this study, the mechanisms of ultrasonic propagation in viscoelastic poly(ethylene oxide) aqueous solution and the interaction between ultrasound and fluid are investigated. A theoretical model of ultrasonic propagation in a viscoelastic fluid is established, in which the body force from ultrasonic waves is added to the fluid momentum equation, and the viscoelasticity of the fluid is described by the Oldroyd-B model. The simulation results for the ultrasonic reflection coefficient at the solid–liquid boundary and the attenuation coefficient based on the multi-physics coupling method are experimentally verified. The results of this study show that the ultrasonic absorption coefficient at low frequencies from 2.25 to 7.5 MHz exhibits frequency dependence through ultrasonic relaxation spectroscopy. The simulation results of the velocity of disturbed flow during ultrasonic propagation show that the viscosity of the solution has a greater impact on the disturbance than the relaxation time, and the phase angle difference between the stress and strain also shows that the viscosity is the main factor affecting the ultrasonic propagation.

Analysis of the laminar flow and enhanced heat transfer rate through a triangular array of cylinders embedded in a fluid-saturated porous media with mixed convection

An investigation of the laminar flow and enhanced heat transfer rate through a triangular array of cylinders embedded in a fluid-saturated porous media is considered. Mixed convection covering forced convection cases has been studied using a finite-volume approach considering the local thermal equilibrium model. Darcy–Brinkman–Forchheimer momentum equations are used to characterize the porous media in question. The study is constrained to the low and intermediate Peclet number (Re = 5 to 40, Pr = 50) and high range of Darcy number (Da = 10−3 to 10−1) for different cylinder spacings (0.7 ≤ φ ≤ 0.99). It is anticipated that porous media would enhance heat transfer, but it derives a multiple order in pressure drop indubitably not desirable in many heat applications. Investigation reveals that both mean drag coefficient (CD ) and Nusselt number (Nu) are strong functions of Da and φ; however, the influence of the buoyancy parameter is mainly witnessed in higher permeability levels and high Peclet numbers. The study also details the effect of governing parameters on mean gap velocities and pressure coefficients. Surprisingly, recirculation wakes exist for the lowest cylinder spacing (φ = 0.7) in high fluid momentum. Low φ and high permeability are desirable in a forced convection regime, whereas both φ and Da should be high in the case of mixed convection. This article also quantifies the combined effect of the Darcy number and buoyancy parameter on the heat-transfer enhancement ratio. A maximum of 112% increase in Nu for φ = 0.7 and 452% for φ = 0.99 are reported at Da = 10−1, but at the cost of higher pressure drop in the latter case.

Electrokinetic energy conversion of high pressure-driven flow with pressure-viscosity effect at high zeta potential

In this study, the electrokinetic energy conversion efficiency is investigated theoretically in high pressure-driven flow with the pressure-viscosity effect. Calculations of the electrokinetic flow in a straight nanochannel are based on the Poisson-Boltzmann equation and modified fluid momentum equation. Once the viscosity of fluid is dependent on the pressure, the strongly non-linear governing equation should be solved simultaneously due to the unknown fluid viscosity. Thus, the domain perturbation method is used to solve the distributions of flow velocity and pressure. Based on obtained velocity and pressure, the maximum conversion efficiency is calculated by thermodynamic analysis. Results show the maximum efficiency increases with the decrease of salt concentration and the peak efficiency can be obtained at sufficiently low salt concentration. For a given salt concentration, the maximum efficiency decreases monotonously with the increase of pressure-viscosity coefficient. Besides, the maximum energy conversion efficiency of ignoring the pressure-viscosity effect is larger than that of considering the pressure-viscosity effect.

Time‐dependent pressure‐driven flow in a horizontal cylinder filled with a bidisperse porous material

AbstractSome properties of time‐dependent that modify Brinkman equations for fluid flow in a cylindrical tube filled with Bidisperse Porous Material are discussed in this article. The fluid velocities through the fracture and porous phases of the Bidisperse Porous Medium (BDPM) resulting from the application of pressure gradient are described by two coupled second‐order partial differential equations. Laplace transform technique, D'Alembert and Riemann‐Sum Approximation Methods are used to obtain a semianalytical solution for the model. The choice of the D'Alembert is made to systematically decouple the coupled governing equations without altering their initial orders. The role of the coupling parameter: The coefficient of momentum transfer in the flow formation is considered. Accordingly, three cases are analyzed: (a) weak coupling which described the fluid flow in the absence of the coupling parameter, (b) the strong coupling resulting from a large value of the coupling parameter , and (c) fluid momentum for any arbitrary value of . It is observed that fluid stability is attained when and are decreased; a finding that agrees with the findings of Nield and Kuznetsov and Magyari. Also, the maximum velocity in the fracture phase of the BDPM is attained when the coefficient of momentum transfer is neglected while an opposing flow formation is demonstrated in the fracture and porous phases of BDPM as is increased.

Thermal radiation effect on Non-Newtonian Casson fluid through a porous material over a magnetic field with buoyancy

The magnetohydrodynamic (MHD) chemically reactive of Casson non-Newtonian nanofluid flow on a two-dimensional incompressible steady from stretched sheet in a porous quiescent medium with buoyancy effect is investigated numerically. Additional effects included in the originality of the model are the applied magnetic field and solar radiation effect. The Chebyshev collocation method (CCM) was used to solve the ordinary differential equations (ODEs) with MATHEMATICA 11.3 software. The present tables and graphs show the performance of fluid physical quantities, momentum flow, energy distribution, nanoparticle concentration, and velocity for various values of applicable dimensionless numbers. The numerical outcomes demonstrate the effect of different physical parameters of the fluid, and it was observed that the velocity profile increased as the thermal and mass Grashof number increased due to an increase in buoyant force caused by heat transferred from the vertical plate to the fluid but decreased as the Casson parameter increased due to a decrease in its yield stress, porosity, and magnetic parameter. Also Analyses reveal that the thermal profile reduce with an increase in variable thermal conductivity parameter. This study will be of considerable economic value to marine engineers, mechanical engineers, physicists, chemical engineers, and others since its application will help them improve their operations.

Fish peduncle response during forward and backward propulsion

Fish is the master of fluid control, with high propulsive efficiency and great maneuverability. Carps are chosen for observations since they are the typical carangiform fish. We add some external stimuli on the fish and observe their responses. It is found that a fish attempts to escape backward or forward depending on the stimuli. The fish tries a greater number of its tail oscillations in a forward escape than in a backward escape. In the case of a forward escape, the retract stroke where the tail gets a concave shape (suitable for higher thrust generation) is faster than the forward stroke where the tail takes a convex shape (suitable for smaller drag), while vice versa in the case of a backward escape. Becoming concave or convex shapes of the tail and being faster or slower strokes all correspond to enhancing fluid momentum in the forward or backward directions where appropriate. The traveling wave of the body propagates backward and forward for the forward and backward escapes, respectively. The results provide a reference for bionic fish design and simulation.

Impact of Newtonian Heating on MHD Micropolar Fluid for the Influence of Heat Source

Introduction: The current analysis deals with the flow of time-independent conducting micropolar fluid past a stretching sheet. Furthermore, the influences of magnetic field strength and heat sources are also discussed in this study. The current study is important for the growing applications of magnetism in various chemical systems like pumping, transportation, trapping, sorting, separation, etc. Aims: In addition, the objective of the present exploration is the consideration of Newtonian heating conditions. Methods: Transformation of nonlinear PDEs of the flow phenomena into nonlinear coupled ODEs is done using suitable similarity variables, and these are handled by employing the “Runge-Kutta fourth-order” scheme in association with the “shooting technique”. The influence of flow characteristics proposed in this study is analyzed via graphs. The engineering coefficients for various parameters are simulated numerically and deployed through the table. Results: Finally, it was found that the rotational viscosity dominates over the fluid viscosity and enhances the momentum profile. Conclusion: An augmentation in the Prandtl number retards the fluid temperature and the application of applied magnetic field built up the resistance that retards fluid momentum.

The flow of a Jeffrey fluid in a composite horizontal channel partially filled with a deformable porous material

AbstractThe flow of a Jeffrey liquid in a composite deformable porous layer is examined. The Jeffrey model governs fluid flow in the free‐flow zone, while the theory of mixtures describes the fluid flow in the deformable porous region. The governing equations are transformed to dimensionless by using appropriate nondimensional quantities. The velocity field is achieved in both the clear flow and deformable porous regions. The displacement expression in the porous zone is also established. The results are discussed for various substantial parameters in detail. It is scrutinized that the flow rate accelerates with a rise in the Jeffrey parameter . Also, it is perceived that the flow rate is less for a Newtonian liquid than the non‐Newtonian Jeffrey liquid. The fluid momentum enhances by increasing the volume fraction of the fluid phase. It is found that the magnitude of skin friction at the clear flow region and porous region grows with an increase in the Jeffrey parameter . Furthermore, it is noticed that the wall shear stress is less for a Newtonian liquid when compared with non‐Newtonian Jeffrey liquid both in the free‐flow region as well as in the porous regions.

Controlling flow separation over a curved ramp using vortex generator microjets

Introducing a fluid microjet into the boundary layer to increase fluid momentum and hence delay separation is a method for actively controlling a flow separation region. The present work numerically analyzed the control of a separation bubble behind a ramp. For this purpose, we first verified the steady-state numerical results for a flow (without a jet) over the ramp against reliable experimental studies from the literature. Next, the effects of introducing a microjet to the flow were also verified. A jet was then placed at three different distances above the ramp to study its impact on various parameters, including velocities, Reynolds stresses, pressure, vorticity, streamlines, and the separation bubble size. As the jet was moved further back, the jet-induced upwash region grew considerably. Finally, the effects of using three identical jets were studied and compared against those of a single jet. The results indicated that using a three-jet array shrank the separation bubble. Using an array with d/D = 15 (distance between microjets over microjet diameter) can limit laterally the separation bubble about 2.75 times smaller than a single jet in the z-direction. Also, the employment of the jet managed to decrease the length of the separation zone in the x-direction up to 78%, in the case of Lx/L1 = 0.0143 (longitudinal distance of microjet from above the ramp over ramp length) and d/D = 10.

The Interaction between High Frequency Electromagnetic Waves with Plasma and the Effect of Negative Ions Existence on the Power Absorption Capability

The interaction between the incident, high frequency, electromagnetic waves with plasma layer shows that the existence of negative ions and the non-linear effect reduces the power absorption capability of the plasma. In this research we study and discuss all parameters of the great influence in this process depending on many important equations, like the Maxwell equations, current response of the plasma equation, multi – fluid momentum equation and the continuity equation. Numerical simulations based on the finite- difference- time- domain approximation to multi- fluid equations for the positive ions, negative ions and electrons are used to study high frequency electromagnetic waves propagation and absorption in an unmagnetized plasma layer. A good agreement in the comparison between the simulations in this work and the experimental results in the previous works is shown.

Numerical study of flow and free convection of water/silver nanofluid in a circular cavity influenced by hot fluid flow

In this numerical study, the numerical simulation of laminar free convection of water/silver nanofluid in a circular cavity under the effect of hot water fluid outside the cavity is carried out. The cooling fluid is water silver nanofluid at a volume concentration of φ = 0–0.06. This study was done for Gr = 102, 103 and 104 using the finite volume method. The Reynolds numbers of Re = 1, 10 and 100 were used. The results of the study show that due to the temperature difference between the cavity and the entering fluid, heat transfer occurs between the hot fluid in the channel and the nanofluid in the cavity at the start of the channel. This temperature difference between the surface and the fluid reinforces the buoyancy force and the Grashof number, intensifying the cavity flow and creating a more uniform cavity temperature distribution. For low Gr number, higher φ results in modest temperature gradient reduction. Using a higher fluid flow, the channel-cavity heat transfer increases which elevate dimensionless temperature curves. At a higher φ, due to the higher fluid viscosity and density, a higher momentum is required for flow convection and circulation. As a result, a stronger buoyancy force aids with free convection intensity, which is effective in elevating the Nusselt number curve values. By increasing the Reynolds number, a higher cavity heat transfer occurs due to the stronger circulating fluid's momentum.

Numerical analysis of unsteady momentum and heat flow of dusty tangent hyperbolic fluid in three dimensions

This paper explores the impact of MHD and viscous dissipation with joule heating on convective stretching flow of dusty tangent hyperbolic fluid over a sheet in 3D. A time-dependent magnetic field is applied along the z-axis and the sheet being stretched along the xy-plane. The fluid and dust particles motions are coupled only through drag and heat transfer between them. The effect of viscous dissipation with convection is appreciable when the generated kinetic energy becomes appreciable as compared to the amount of heat transferred. A well known bvp4c method has been used to find the fruitful results. Graphs and tables show the facts and figures for physical properties according to different parameters. The main findings are that Increase in power law index, magnetic field, Weissenberg effect, concentration of dust particles, and unsteadiness parameter reduces the flow of fluid and solid granules.

Heat transfer and entropy analysis for nanofluid flow in a semi-circular open cavity under mixed convection

This paper presents a numerical simulation of nanofluid flowing in an open cavity under mixed convection by considering various heat transfer zones. To enhance the heat transfer, water was augmented with copper nanoparticles at different ϕ (volume fraction of nanoparticles) values. The present paper aims to determine the optimal position which maximizes the heat transfer in a circular open cavity. Also, in this research the investigation of combined convection flow in a specific geometry, taking into account the changes in the flow parameters, is an attempt to model the temperature field and heat transfer. For this purpose, the nanofluid flow for Reynolds numbers of Re =10, 50 and 100 is investigated. On the other hand, the hot areas in the curved part of the open cavity are separated in various cases. The results show that due to the low velocity of the fluid in the circular part of the cavity, especially in the hot wall area, most of the fluid exchange is due to natural convection due to density difference and the hot areas are strengthen the flow circulation. The exchange is also improved by increasing Re (Reynolds number) or the momentum term, and the distribution of T (temperature) in the cavity becomes more uniform. Hot spots with low heat transfer coefficient were attenuated at higher Re. The most suitable temperature distributions were achieved for W4 and W2. By increasing ϕ, the friction factor decreases for pure water, especially in W2 and W3. However, due to fluid-surface impact at Re = 100 in W2 and W3, the friction factor does not change significantly by altering ϕ. Using a higher Re and the dominance of the fluid momentum in comparison with the viscous force, the effect of nanoparticle concentration decreases. In general, the best heat transfer occurs at higher volume fraction of nanoparticles. Finally, at all Reynolds numbers, the heat transfer increases by 8–19%. This is because nanoparticles are added to pure water (working fluid).

Numerical Calculations of Liquid-Metal Magnetohydrodynamic Flows Through Circular Pipe in Magnetic Field Inlet Region and Outlet Region

Numerical calculations are conducted for liquid-metal magnetohydrodynamic flows through a circular pipe with an electrically conducting wall in both the magnetic field inlet region and the outlet region. Conservation equations of fluid mass and of fluid momentum and the Poisson equation for electrical potential are solved numerically. The calculations are performed by a cylindrical coordinate system using a staggered grid in order to obtain numerically stable solutions, covering Hartmann numbers up to the order of 10 000. As to the loss coefficient ζ for the pressure drop, the value of ζ/(Ha2/Re) does not depend on the Ha number, the Re number, and the wall conductance ratio very much for both the magnetic field inlet section and the outlet section. The value of ζ/(Ha2/Re) changes mainly with the gradient of the applied magnetic field for both the magnetic field inlet section and the outlet section.

A base for the log law and von Karman’s constant problem

ABSTRACT The log-law profile equation and its intrinsic von Karman’s constant are widely used in fluid mechanics. Despite numerous theoretical and empirical attempts to establish formal bases for these concepts, no consensus has been reached. We review past work and present a simple rolling eddy model of boundary-layer turbulence. We consider fluid momentum loss from eddies that roll out over smaller eddies on a timescale that matches the shear interaction of the eddies with the boundary. The resulting parametric form for eddy scaling provides a basis for comprehending turbulent boundary-layer flow as an exponential growth process. The outward-rolling-eddy model formulation yields a log law and explanation for von Karman’s constant. Results of the model are compared with instantaneous flow imagery and direct numerical simulations. The model implies that changes in von Karman’s constant indicate changes in the underlying eddy self-similarity pattern. The approach gives a new perspective on an old problem.

An implicit Cartesian cut-cell method for incompressible viscous flows with complex geometries

A versatile conservative three-dimensional Cartesian cut-cell method for simulation of incompressible viscous flows over complex geometries is presented in this paper. The present method is based on the finite volume method on a non-uniform staggered grid together with a consistent mass and momentum flux computation. Contrary to the commonly cut-cell methods, an implicit time integration scheme is employed in the present method, which avoids numerical instability without any additional small cut-cell treatment. Strict conservation of the mass and momentum for both fluid and cut cells is enforced through the PISO algorithm for the pressure–velocity coupling. The versatility and robustness of the present cut-cell method are demonstrated by simulating various two- and three-dimensional canonical benchmarks (flow over a circular cylinder, airfoil, sphere, pipe, and heart sculpture) and the computed results agree well with previous experimental measurements and various numerical results obtained from the boundary-fitted, immersed boundary/interface, and other cut-cell methods, verifying the accuracy of the proposed method.

Shape Optimization of the Momentum Ring Cross Section for Satellite Attitude Control Based on Magnetohydrodynamics

Compared with the traditional actuator, the fluid momentum controller actuator based on magnetohydrodynamics (MHD) has some unique advantages and characteristics. In this paper, a method is proposed for the shape optimization of fluid momentum ring cross section. Based on the engineering situation, this article proposes a mathematical model of angular momentum that can be used for analytical calculations. Second, the two shapes obtained are unified and mathematically expressed in terms of maximum power and minimum resistance, respectively. Finally, the particle swarm algorithm is used to optimize the parameters of the proposed shape in combination with finite element method (FEM). Compared with the common rectangular section scheme, the attitude adjustment performance of fluid momentum ring can be effectively improved. Specifically, for the same area of cross section, the fluid momentum rings with the proposed shape provide the angular momentum values that exceed those of the rectangular shape by 14%-17% for the cases considered. This method avoids the huge computation of computational fluid dynamics and multidisciplinary topology optimization.

Natural convection simulation of Prabhakar-like fractional Maxwell fluid flowing on inclined plane with generalized thermal flux

This study considers the natural convection of viscoelastic fractional-type Maxwell fluid flowing on an inclined oscillating plate with generalized equations for stress-shear and thermal flux of thickness vector. A recent and modified fractional technique, namely Prabhakar fractional derivative, is utilized for the generalized memory effect. The solution of non-dimensional and transformed governed equations is explored by integral transform. Prabhakar-like fractional-Maxwell fluid's energy and momentum profiles are compared with classical Fourier thermal flux and ordinary Maxwell fluid with generalized heat transport. To see insight into the physical behavior of the governed equations, different exceptional cases of momentum profiles are described whose physical significance is well-explained in the existing literature, and also the graphical interpretation is presented for the comparison and influence of all parameters on momentum and energy fields. As a result, we have concluded that the Prabhakar fractional operators signify the possibility of a convenient choice of different fractional constraints, which has good fitting in both experimental and theoretical data. Furthermore, the ordinary-type Maxwell fluid with Fourier thermal flux represents less velocity rate as compared to ordinary Maxwell fluid with fractional thermal flux and fractional Maxwell fluid with fractional thermal flux.

Magnetic-hybrid nanoparticles with stretching/shrinking cylinder in a suspension of MoS4 and copper nanoparticles

The main intent of the present study is to explore the varying fluid momentum and thermal energy characteristics of the laminar, steady, incompressible, two-dimensional, non-Newtonian pseudo plastic Williamson hybrid nanofluid over a stretching cylinder with variability in thermal conduction, suction, injection, heat generation and magneto hydrodynamic effects are considered. The mixture of Cu and MoS4 as nanoparticles in water as its base fluid is taken for this investigation as an hybrid nanofluid. The formulated governing PDEs are modified by employing with appropriate dimensionless transformations to get the non-linear ordinary differential equations. In accordance with the help of Runge-Kutta method of order four, shooting technique is implemented by making use of boundary value problem solver, bvp4c, which is accessible as an in-built function in MATLAB software for the numerical solution of the problem. The finding of this study are The values of Cf of the fluid grows with an increasing values of the physical parameters such as M and γ, whereas it is negatively influenced by λ. The values Nu of the Williamson hybrid Nano fluid has an increasing effect for the ascending entries of γ as well as Pr and has a reverse effect for the values of λ, M, β and ε of the fluid flow.