Influence of variable viscosity the peristaltic flow of pseudoplastic fluid in a tapered channel is discussed. The effects of magnetohydrodynamics (MHD) are also studied. Asymmetric channel is considered. The relevant problem is first formulated and then non-dimensionalized. The nonlinear different system subject to lubrication approach is solved. Expressions for pressure gradient, pressure rise and velocity are constructed. Graphs reflecting the variations of sundry parameters on pressure rise and velocity are examined. Trapping and pumping phenomena are also studied.

We investigate several robust preconditioners for solving the saddle-point linear systems that arise from spatial discretization of unsteady and steady variable-coefficient Stokes equations on a uniform staggered grid. Building on the success of using the classical projection method as a preconditioner for the coupled velocity pressure system [B. E. Griffith, J. Comp. Phys., 228 (2009), pp. 7565-7595], as well; established techniques for steady and unsteady Stokes flow in the finite-element literature, we construct preconditioners that employ independent generalized Helmholtz and Poisson solvers for the velocity and pressure subproblems. We demonstrate that only a single cycle of a standard geometric multigrid algorithm serves as an effective inexact solver for each of these subproblems. Contrary to traditional wisdom, we find that the Stokes problem can be solved nearly as efficiently as the independent pressure and velocity subproblems, making the overall cost of solving the Stokes system comparable to the cost of classical projection or fractional step methods for incompressible flow, even for steady flow and in the presence of large density and viscosity contrasts. Two of the five preconditioners considered here are found to be robust to GMRES restarts and to increasing problem size, making them suitable for large-scale problems. Our work opens many possibilities for constructing novel unsplit temporal integrators for finite-volume spatial discretizations of the equations of low Mach and incompressible flow dynamics.

The paper is devoted to a study of steady hydromagnetic fluid flow with heat and mass transfer over an inclined nonlinear shrinking porous sheet in the presence of thermophoresis and heat generation. The problem is formulated as a non-linear boundary value problem. A numerical method is developed to solve the problem. The surface velocity of the shrinking sheet and the applied transverse magnetic field are considered as power functions of the distance from the origin. The viscosity and thermal conductivity of the fluid are considered temperature-dependent. The viscosity is taken to be an inverse function of temperature, while the thermal conductivity is supposed to vary linearly with temperature. By using suitable transformation, the equations governing the flow, temperature and concentration fields are reduced to a system of coupled non-linear ordinary differential equations, which are solved numerically by developing an appropriate numerical method. Velocity, temperature and concentration profiles as well as the skin-friction coefficient and wall heat transfer are studied with particular emphasis. Their variations with different parameters are investigated. The computed numerical results are presented graphically.

A numerical study has been carried out to analyze the constant heat flux, internal heat generation, variable viscosity and thermal radiation effects on the flow and heat transfer of a Newtonian fluid over an exponentially stretching porous sheet. Using a similarity transformation, the governing partial differential equations are transformed into coupled, non-linear ordinary differential equations with variable coefficients. Numerical solutions to these equations subject to appropriate boundary conditions are obtained by using an efficient Chebyshev spectral method. The effects of various physical parameters such as viscosity parameter, the suction parameter, the radiation parameter, internal heat generation or absorption parameter and the Prandtl number on velocity and temperature are discussed by using graphical approach. Moreover, numerical results indicate that in the presence of constant heat flux, the skin-friction coefficient as well as Nusselt number is strongly affected by the viscosity parameter, suction parameter, radiation parameter and the internal heat generation parameter.

The effects of variable viscosity and thermal conductivity on the natural convection heat transfer over a vertical plate embedded in a porous medium saturated by a nanofluid are investigated. In the nanofluid model, a gradient of nanoparticles concentration because of Brownian motion and thermophoresis forces is taken into account. The nanofluid viscosity and the thermal conductivity are assumed as a function of local nanoparticles volume fraction. The appropriate similarity variables are used to convert the governing partial differential equations into a set of highly coupled nonlinear ordinary differential equations, and then, they numerically solved using the Runge-Kutta-Fehlberg method. The practical range of non- dimensional parameters is discussed. The results show that the range of Lewis number as well as Brownian motion and thermophoresis parameters which were used in previous studies should be reconsidered. The effect of non-dimensional parameters on the boundary layer is examined. The results show that the reduced Nusselt number would increase with increase of viscosity parameter and would decrease with increase of thermal conductivity parameter.