Variable Viscosity Fluid Research Articles

Unsteady MHD convection heat transfer along an accelerating/decelerating cylinder with variable fluid properties

In this work we endeavor to obtain the analytical solutions for the unsteady MHD mixed convection of an electrically conducting viscous fluid over a vertical accelerating/decelerating cylinder. Unlike typical studies, the temperature-dependent fluid properties, variable fluid viscosity and the thermal conductivity are studied in highly coupled velocity and temperature fields. The locally similar and nonlinear coupled parabolic partial differential equations (PDEs) with exponential growth/decay boundary condition are solved by homotopy analysis method (HAM). The analytical results are compared with numerical solutions in an excellent agreement. The combined effects of pertinent physical parameters, such as the unsteadiness parameter, the temperature-dependent viscosity parameter, the temperature-dependent thermal conductivity parameter, the magnetic parameter and the mixed convection parameter on the flow and heat transfer characteristics are analyzed and discussed.

Soret and Dufour Effects on Peristaltic Transport of MHD Fluid with Variable Viscosity

This article looks at the Soret and Dufour effects on the magnetohydrodynamic (MHD) peristaltic flow of variable viscosity fluid in a symmetric channel. Analysis is presented in the presence of Ohmic heating. Results for the stream function, temperature and concentration are constructed. The variations of sundry parameters are analyzed.

Effect of Variable Viscosity, Dufour, Soret and Thermal Conductivity on Free Convective Heat and Mass Transfer of Non-Darcian Flow past Porous Flat Surface

The motion of incompressible fluid of a variable fluid viscosity and variable thermal conductivity with thermal radiation, Dufour, Soret with heat and mass transfer over a linearly moving porous vertical semi-infinite plate with suction is investigated. The governing equations are transformed into a system of coupled nonlinear ordinary differential equations using similarity transformations with dimensionless variables and solved numerically using shooting method with Runge-Kutta fourth-order method and Newton-Raphson’s interpolation scheme implemented in MATLAB. The result showed that with increase in Dufour and Soret parameter, fluid velocity increases and temperature increases with increase in variation of Dufour while, temperature decreases with increase in Soret. The effects of variable fluid viscosity, variable thermal conductivity, thermal radiation, Soret, Dufour, Prandtl and Schmidt parameters on the dimensionless velocity, temperature and concentration profiles are shown graphically.

Analysis of viscosity effect on turbine flowmeter performance based on experiments and CFD simulations

Viscosity effect is one important factor that affects the performance of turbine flowmeter. The fluid dynamics mechanism of the viscosity effect on turbine flowmeter performance is still not fully understood. In this study, the curves of meter factor and linearity error of the turbine flowmeter changing with fluid viscosity variations were obtained from multi-viscosity experiments (the viscosity range covered is 1.0×10–6m2/s–112×10–6m2/s). The results indicate that the average meter factor of turbine flowmeter decreases with viscosity increases, while the linearity error increases. Furthermore, Computational Fluid Dynamics (CFD) simulation was carried out to analyze three-dimensional internal flow fields of turbine flowmeter. It was demonstrated that viscosity changes lead to changes of the wake flow behind the upstream flow conditioner blade and the flow velocity profile before fluid entering turbine rotor blade, which affect the distribution of pressure on the rotor blades, so impact the turbine flowmeter performance.

Effects of thermal radiation and variable fluid viscosity on stagnation point flow past a porous stretching sheet

Similarity analysis is performed to investigate the structure of the boundary layer stagnation-point flow and heat transfer over a stretching sheet subject to suction. Fluid viscosity is assumed to vary as a linear function of temperature. Thermal radiation term is considered in the energy equation. The symmetry groups admitted by the corresponding boundary value problem are obtained by using a special form of Lie group transformations viz. scaling group of transformations. With the help of them the partial differential equations corresponding to momentum and energy equations are transformed into highly non-linear ordinary differential equations. Numerical solutions of these equations are obtained by shooting method. It is found that the horizontal velocity increases with the increasing values of the ratio of the free stream velocity to the stretching velocity. Velocity increases with the increasing temperature dependent fluid viscosity parameter when the free-stream velocity is less than the stretching velocity but opposite behavior is noted when the free-stream velocity is greater than the stretching velocity. Due to suction, fluid velocity decreases at a particular point of the surface. Temperature at a point of the surface is found to decrease with increasing thermal radiation.

Entropy analysis for third-grade fluid flow with temperature-dependent viscosity in annulus partially filled with porous medium

In the present paper, a non-Newtonian third-grade fluid flow is considered in an annulus partially filled by a porous medium of very small permeability. An analytical solution by the perturbation series method is obtained for velocity and temperature fields, assuming Reynolds?s model to account for the variation of fluid viscosity with temperature. The effects of various pertinent parameters on the flow field, temperature field and entropy generation number are obtained and discussed graphically.

The Flow of a Variable Viscosity Fluid down an Inclined Plane with a Free Surface

The effect of a temperature dependent variable viscosity fluid flow down an inclined plane with a free surface is investigated. The fluid film is thin, so that lubrication approximation may be applied. Convective heating effects are included, and the fluid viscosity decreases exponentially with temperature. In general, the flow equations resulting from the variable viscosity model must be solved numerically. However, when the viscosity variation is small, then an asymptotic approximation is possible. The full solutions for the temperature and velocity profiles are derived using the Runge-Kutta numerical method. The flow controlling parameters such as the nondimensional viscosity variation parameter, the Biot and the Brinkman numbers, are found to have a profound effect on the resulting flow profiles.

A Hybrid Grid-Particle Method for Moving Bodies in 3D Stokes Flow with Variable Viscosity

This article presents a new approach for the resolution of large three-dimensional Stokes equations with variable viscosity fluids, coupled with transport equations. After building the model, we will write these equations in the context of highly viscous flows and penalization, in order to consider complex geometries moving in a fluid. From a mathematical point of view, the solutions show nonlinear dynamics. Beside the use of standard tools such as finite differences and staggered grids, we have built a new methodology based on large three-dimensional simulations, including operators splitting for an efficient use of fast solvers, multi-index fixed point methods, Lagrangian methods with fast and accurate grid-particle transfers, and the multiresolution description of variables. Among the main original aspects of this method, both accurate incompressibility and variable viscosity are treated in the same fixed point. Hence the computation costs for variable and constant viscosity flows are similar. Several ...

Heat Transfer Phenomena in a Moving Nanofluid Over a Horizontal Surface

AbstractA numerical study is carried out to study the effects of variable fluid properties on the boundary layer flow and heat transfer of a nanofluid at a flat sheet. The effects of Brownian motion, thermophoresis and viscous dissipation due to frictional heating are also considered. The temperature-dependent variable fluid properties, namely, the fluid viscosity and the thermal conductivity are assumed to vary, respectively, as an inverse function and a linear function of temperature. Using a similarity transformation, the governing non-linear partial differential equations of the model problem are transformed into coupled non-linear ordinary differential equations and these equations are solved numerically by Keller-Box method. Velocity, temperature, and nanoparticles volume fraction profiles are presented and analyzed for several sets of values of the governing parameters; namely, variable fluid viscosity, variable thermal conductivity, Brownaian motion, thermophoresis and plate-velocity parameters with changes in the Prandtl and Schmidt numbers. It is observed that there is an increase in the skin friction in the upstream movement of the plate: But quite the opposite is true in the downstream movement of the plate. Also, the effect of the Schmidt number and the Brownian motion parameter is to reduce the Sherwood number, where as the effect of thermophoresis parameter is to enhance it.

High shear helical flow of a Sisko fluid

The Sisko fluid model was proposed in response to observed failure of the well-known Bingham model to represent the flows of viscoplastic materials in high shear regimes, such failure increasing with shear rate. We consider the flow of a Sisko fluid between infinitely long coaxial cylinders, when the inner cylinder rotates with constant angular speed and a constant axial fluid flow is maintained. High shear rates are ensured by assuming an inter-cylindrical gap small in relation to the overall geometry. Such a helical flow and geometry is of relevance to a number of applications, including rheometry. We assume a laminar flow and apply a perturbation procedure based on a scaled form of the inter-cylindrical gap dimension as a perturbation parameter to obtain simple explicit approximations for the fluid velocity field as well as the fluid viscosity variation in this gap. We also derive an approximate form of the Reiner--Riwlin equation, linking the defining fluid parameters to measurable quantities in the flow. References R. B. Bird, R. C. Armstrong and D. Hassager, Dynamics of Polymetric liquids, Vol. 1, John Wiley and Sons, 1987. C. Chiera, Perturbation Analysis of the Helical Flow of Generalized Newtonian Fluids, Ph.D. Thesis, RMIT, 2004 C. Chiera, H. J. Connell and J. J. Shepherd, Perturbation analysis of the helical flow of non-Newtonian fluids with application to a recirculating coaxial cylinder rheometer, Mathematical and Computer Modelling, 18, No 10: 131--140, 1993. doi:10.1016/0895-7177(93)90222-K C. Chiera, H. J. Connell and J. J. Shepherd, On the helical flow of a Sisko model fluid, Proc. 2nd Pacific Rim Conf. Rheology (PRCR2), Melbourne, Australia, 33--34, July 1997 B. D. Coleman and W. Noll, Helical flow of General Fluids, J. App. Phys., 10: 1508--1512, 1959. doi:10.1063/1.1734990 M. T. Farrugia, J. J. Shepherd and A. J. Stacey, A perturbation analysis of the flow of a Powell--Eyring fluid between coaxial cylinders, ANZIAM J., 52 257--270, 2011. http://journal.austms.org.au/ojs/index.php/ANZIAMJ/article/view/3748 W. E. Langlois, Slow Viscous Flow, Macmillan, New York, 1964 A. W. Sisko, The flow of lubricating greases, Ind. and Eng. Chem., 50 (12), 1789--1792, 1958 http://pubs.acs.org/doi/abs/10.1021/ie50588a042

Analysis of unsteady flow of a variable viscosity reactive fluid in a slit with wall suction or injection

The coupled nonlinear equations, in rectangular Cartesian coordinates, governing the heat transfer and unsteady pressure-driven flow of a reactive variable viscosity fluid in a thin stationary slit, whose walls are porous, are derived and solved numerically using a semi-implicit finite difference scheme. The chemical kinetics and the temperature dependent viscosity are assumed to follow the Arrhenius rate law. Both numerical and graphical results are presented and discussed quantitatively with respect to various parameters embedded in the problem.

UNSTEADY BLOOD FLOW IN AN ARTERY WITH AN OVERLAPPING STENOSIS

We consider the problem of unsteady blood flow in an artery and in the presence of an overlapping symmetric stenosis. The blood flow in the arterial tube is assumed to be a suspension of red cells in plasma. The present formulation makes use of the variable fluid viscosity modeling that takes into account the amount of the red cells in the blood fluid flow system. Using both analytical and computational methods, we determine the expression for various quantities such as the leading order flow velocity, pressure gradient, impedance and shear stress at the throats and at the critical height, and we calculate dependence of these quantities on the temporal and spatial variables as well as on the frequency of the flow oscillation and the main parameters of the flow system. We find, in particular, that the higher value of the frequency can lead to higher values of the magnitude for the quantities such as the axial velocity, the impedance and the wall shear stress in the stenosis zone particularly if the stenosis is less mild.

Thermophoresis particle deposition on unsteady two-dimensional forced convective heat and mass transfer flow along a wedge with variable viscosity and variable Prandtl number

In this paper, the effects of thermophoresis particle deposition on an unsteady two dimensional forced convective heat and mass transfer flow past a wedge taking into account the variation of fluid viscosity and fluid Prandtl number with temperature are studied. The local similarity equations are derived and solved numerically using Nachtsheim–Swigert shooting iteration technique along with the sixth order Runge–Kutta integration scheme. Comparisons with previously published work are performed, and the results are found to be in excellent agreement. Results for the non-dimensional velocity, temperature, concentration, Prandtl number and thermophoretic velocity are displayed graphically whereas thermophoretic deposition velocity is shown in the tabulated form for various values of the pertinent parameters. The obtained numerical results show that in modeling the thermal boundary-layer flow with a temperature-dependent viscosity, consideration of the Prandtl number as a constant within the boundary layer produces unrealistic results, and therefore, it must be treated as a variable rather than a constant within the boundary layer. The results also show that the thermophoretic particle deposition velocity decreases as the thermophoretic coefficient increases.

Simulation of Variable Viscosity and Jeffrey Fluid Model for Blood Flow Through a Tapered Artery with a Stenosis

Non-Newtonian fluid model for blood flow through a tapered artery with a stenosis and variable viscosity by modeling blood as Jeffrey fluid has been studied in this paper. The Jeffrey fluid has two parameters, the relaxation time λ1 and retardation time λ2. The governing equations are simplified using the case of mild stenosis. Perturbation method is used to solve the resulting equations. The effects of non-Newtonian nature of blood on velocity profile, temperature profile, wall shear stress, shearing stress at the stenotsis throat and impedance of the artery are discussed. The results for Newtonian fluid are obtained as special case from this model.

Peristaltic Pumping of a Fluid of Variable Viscosity in a Non Uniform Tube/Channel with Permeable Wall

In this paper, the peristaltic flow of a fluid of variable viscosity in a non uniform tube or channel lined with porous material is studied. This model is suitable for the pumps whose inner surface of the tube is rough, the roughness that arises due to corrugations plays an important role in pumping and in the biological systems such as blood vessels containing tissue region. The flow in the free flow of the tube is governed by Navier-Stokes equation and the flow in the permeable boundary is described by Darcy law. It is observed that the magnitude of peak pressure rise decreases with increase in flow rate and increases with increasing amplitude ratio and increasing Darcy number. It shows that the larger the permeability of porous medium, the greater the pressure rise against which the pump works. It is also observed that as the viscosity decreases the pressure rise increases and for different values of mean flow rate the frictional force exhibits opposite behavior to that of pressure rise. The trough in the frictional force increases with decreasing amplitude ratio and decreases with increasing Darcy number which shows that the increase in permeability of wall causes less frictional forces. The decrease in viscosity makes the peristaltic pump to work under less frictional force.

Viscosity Variations of Three-Component Mixtures Comprising an Alcohol, Various Common Groundwater Contaminants, and Water

This study investigates the variations in fluid viscosity as water was continuously added to a mixture containing methanol and a common groundwater liquid contaminant. Three different liquid contaminants were considered, namely benzene, toluene, and trichloroethylene. Each methanol-contaminant mixture (50%–50% by volume) was initially a single-phase solution, but partitioned into a two-phase liquid–liquid system after the total water content of the system reached a critical value. After the mixture partitioned into a two-phase system, fluid viscosities of each liquid phase were determined as more water was added to the system. A modified falling-ball viscometer was used to determine the viscosity of each mixture. Results from the viscosity experiments showed that in the single-phase region, the observed mixture viscosity increased with increasing total water content. In the two-phase region, the observed viscosity of the aqueous phase increased with increasing total water content, and then the viscosity decreased after reaching a maximum value. The observed viscosity of the nonaqueous phase decreased initially with increasing total water content, and then the viscosity remained relatively invariant as more water was added to the system. The viscosity variation in the aqueous phase was observed to be much more significant than the viscosity variation in the nonaqueous phase. The observed aqueous phase viscosity can range from 0.95 centipoise (pure water) to a maximum of approximately 1.7 centipoise. Finally, a viscosity model was used to compare the experimentally observed viscosity against the model-derived viscosities. In the single-phase region, modeling results showed that the average absolute deviation errors were fairly small for the three systems considered in this study (ranged between 2.35% and 5.12%). In the two-phase region, the errors were relatively higher in the aqueous phase (ranged between 7.78% and 10.63%) than in the nonaqueous phase (ranged between 3.33% and 6.20%).

3D Surface Roughness Effects on Transient Non-Newtonian Response of Dynamically Loaded Journal Bearings

The influence of 3D surface roughness on the transient non-Newtonian response of a dynamically loaded journal bearing under mixed lubrication is studied. A study of the transient non-Newtonian response of a dynamically loaded journal bearing under mixed lubrication condition is performed including the effects of 3D surface roughness parameters such as roughness orientation and characteristics of surface roughness of opposing surfaces and the variation of fluid viscosity across and along the fluid-film thickness due to shear thinning and viscoelastic behavior of the lubricant. The Reynolds equation is modified to include the effects of surface roughness, viscosity variation across the fluid-film, and viscoelastic properties of the lubricant. The power law model and Maxwell's model are employed to characterize shear thinning and viscoelastic properties of the lubricant, respectively. The solution of the modified average Reynolds equation is obtained using a finite element method and appropriate iterative schemes. Results are presented for a journal bearing subjected to sinusoidal loading. The bearing transient response was found to be significantly affected by the characteristics of surface roughness of opposing surfaces. The bearing with stationary roughness was observed to have good load-carrying capacity.

Boundary Layer Flow and Heat Transfer with Variable Fluid Properties on a Moving Flat Plate in a Parallel Free Stream

The steady boundary layer flow and heat transfer of a viscous fluid on a moving flat plate in a parallel free stream with variable fluid properties are studied. Two special cases, namely, constant fluid properties and variable fluid viscosity, are considered. The transformed boundary layer equations are solved numerically by a finite‐difference scheme known as Keller‐box method. Numerical results for the flow and the thermal fields for both cases are obtained for various values of the free stream parameter and the Prandtl number. It is found that dual solutions exist for both cases when the fluid and the plate move in the opposite directions. Moreover, fluid with constant properties shows drag reduction characteristics compared to fluid with variable viscosity.

Analysis of entropy generation in a variable viscosity fluid flow between two concentric pipes with a convective cooling at the surface

Entropy generation rate in a variable viscosity liquid flowing steadily through two concentric cylindrical pipes with convective cooling at the pipe surface, are studied using the second law analysis. The outer system is assumed to exchange heat with the ambient following Newton’s cooling law, and the fluid viscosity model varies as an inverse linear function of temperature. The resulting equations and the boundary conditions are solved using the fourth Order Runge-Kutta scheme and an efficient shooting technique. Numerical expressions for fluid velocity and temperature are derived and utilised to obtain expressions for volumetric entropy generation numbers, irreversibility distribution ratio and the Bejan number in the flow field. Key words: Pipe flow, variable viscosity, entropy generation, convective cooling, irreversibility analysis.

The Effect of Fluid Viscosity on the Hemodynamic Energy Changes During Operation of the Pulsatile Ventricular Assist Device

Blood viscosity during operation of ventricular assist device (VAD) can be changed by various conditions such as anemia. It is known generally that the blood viscosity can affect vascular resistance and lead to change of blood flow. In this study, the effect of fluid viscosity variation on hemodynamic energy was evaluated with a pulsatile blood pump in a mock system. Six solutions were used for experiments, which were composed of water and glycerin and had different viscosities of 2, 2.5, 3, 3.5, 4, and 4.5 cP. The hemodynamic energy at the outlet cannula was measured. Experimental results showed that mean pressure was increased in accordance with the viscosity increase. When the viscosity increased, the mean pressure was also increased. However, the flow was decreased according to the viscosity increase. Energy equivalent pressure value was increased according to the viscosity-induced pressure rise; however, surplus hemodynamic energy value did not show any apparent changing trend. The hemodynamic energy made by the pulsatile VAD was affected by the viscosity of the circulating fluid.