Peri K. Kameswaran

Homogeneous-heterogeneous reactions in micropolar fluid flow from a permeable stretching or shrinking sheet in a porous medium

The effects of a homogeneous-heterogeneous reaction on steady micropolar fluid flow from a permeable stretching or shrinking sheet in a porous medium are numerically investigated in this paper. The model developed by Chaudhary and Merkin (Fluid Dyn. Res. 16:311-333, 1995) for a homogeneous-heterogeneous reaction in boundary layer flow with equal diffusivities for reactant and autocatalysis is used and extended in this study. The uniqueness of this problem lies in the fact that the solutions are possible for all values of the stretching parameter λ>0, while for λ<0 (shrinking surface), solutions are possible only for a limited range of values. The effects of physical and fluid parameters such as the stretching parameter, micropolar parameter, permeability parameter, Schmidt number, strength of homogeneous and heterogeneous reaction parameter on the skin friction, velocity and concentration are analyzed, and these results are presented through graphs. The solute concentration at the surface is found to decrease with the strength of the homogeneous reaction, and to increase with heterogeneous reactions, the permeability parameter and stretching or shrinking parameters. The velocity at the surface was found to increase with the micropolar parameter.

Dual solutions of stagnation-point flow of a nanofluid over a stretching surface

The paper discusses the effects of homogeneous-heterogeneous reactions on stagnation-point flow of a nanofluid over a stretching or shrinking sheet. The model presented describes mass transfer in copper-water and silver-water nanofluids. The governing system of equations is solved numerically, and the study shows that dual solutions exist for certain suction/injection, stretching/shrinking and magnetic parameter values. Comparison of the numerical results is made with previously published results for special cases.

Thermophoretic and Nonlinear Convection in Non-Darcy Porous Medium

In this paper, we study the effects of nonlinear convection and thermophoresis in steady boundary layer flow over a vertical impermeable wall in a non-Darcy porous medium. Both the fluid temperature and the solute concentration are assumed to be nonlinear while at the wall, both the temperature and concentration are maintained at a constant value. A similarity transformation was used to obtain a system of nonlinear ordinary differential equations, which were then solved numerically using the Matlab bvp4c solver. A comparison of the numerical results with previously published results for special cases shows a good agreement. The effects of the nonlinear temperature and concentration parameters on the velocity and heat and mass transfer are shown graphically. A representative sample of the results is presented showing the effects of thermophoresis on the fluid velocity and heat and mass transfer rates. It is found among other results, that the concentration profiles decreased with increasing values of the thermophoretic parameter.

On radiation effects on hydromagnetic Newtonian liquid flow due to an exponential stretching sheet

The paper investigates the radiation effect on the magnetohydrodynamic Newtonian fluid flow over an exponentially stretching sheet. The effects of frictional heating and viscous dissipation on the heat transport are taken into account. The governing partial differential equations are transformed into ordinary differential equations using a suitable similarity transformation. Zero-order analytical solutions of the momentum equation and confluent hypergeometric solutions of heat and mass transport equations are obtained. The accuracy of analytical solutions is verified by numerical solutions obtained using a shooting technique that uses a Runge-Kutta-Felhberg integration scheme and a Newton-Raphson correction scheme. The effects of the radiation parameter, the magnetic parameter, Gebhart and Schmidt numbers on the momentum, heat and mass transports are discussed. The skin friction and heat and mass transfer coefficients for various physical parameters are discussed.

A new algorithm for internal heat generation in nanofluid flow due to a stretching sheet in a porous medium

Purpose – The purpose of this paper is to study heat and mass transfer in copper-water and silver-water nanofluid flow over stretching sheet placed in saturated porous medium with internal heat generation or absorption. The authors further introduce a new algorithm for solving heat transfer problems in fluid mechanics. The model used for the nanofluid incorporates the nanoparticle volume fraction parameter and a consideration of the chemical reaction effects among other features. Design/methodology/approach – The partial differential equations for heat and mass transfer in copper-water and silver-water nanofluid flow over stretching sheet were transformed into a system of nonlinear ordinary differential equations. Exact solutions for the boundary layer equations were obtained in terms of a confluent hypergeometric series. A novel spectral relaxation method (SRM) is used to obtain numerical approximations of the governing differential equations. The exact solutions are used to test the convergence and accu...

A spectral relaxation method for thermal dispersion and radiation effects in a nanofluid flow

In this study we use a new spectral relaxation method to investigate heat transfer in a nanofluid flow over an unsteady stretching sheet with thermal dispersion and radiation. Three water-based nanofluids containing copper oxide CuO, aluminium oxide Al2O3 and titanium dioxide TiO2 nanoparticles are considered in this study. The transformed governing system of nonlinear differential equations was solved numerically using the spectral relaxation method that has been proposed for the solution of nonlinear boundary layer equations. Results were obtained for the skin friction coefficient, the local Nusselt number as well as the velocity, temperature and nanoparticle fraction profiles for some values of the governing physical and fluid parameters. Validation of the results was achieved by comparison with limiting cases from previous studies in the literature. We show that the proposed technique is an efficient numerical algorithm with assured convergence that serves as an alternative to common numerical methods for solving nonlinear boundary value problems. We show that the convergence rate of the spectral relaxation method is significantly improved by using the method in conjunction with the successive over-relaxation method.

Thermal dispersion effects on convective heat and mass transfer in an Ostwald de Waele nanofluid flow in porous media

In this paper we investigate the effects of thermal dispersion on non-Newtonian power-law nanofluid flow over an impermeable vertical plate. We use a mathematical model for the nanofluid that incorporates the effects of nanoparticle Brownian motion and thermophoresis. The non-Newtonian nature of the fluid is modeled by the power-law index n, and both cases of shear thinning and thickening are investigated. The governing set of equations is solved numerically using the shooting technique. The effects of physical and fluid parameters on the properties are determined for both instances of aiding and opposing buoyancy force. We show, inter alia, that for fixed thermal dispersion coefficient values, the fluid temperature within the boundary layer decreases as the power-law index increases for both aiding and opposing buoyancy case.

Activation energy and binary chemical reaction effects in mixed convective nanofluid flow with convective boundary conditions

Abstract In this paper, we present a theoretical study of the combined effects of activation energy and binary chemical reaction in an unsteady mixed convective flow over a boundary of infinite length. The current study incorporates the influence of the Brownian motion, thermophoresis and viscous dissipation on the velocity of the fluid, temperature of the fluid and concentration of chemical species. The equations are solved numerically to a high degree of accuracy using the spectral quasilinearization method. Brownian motion was noted as the main process by which the mass is transported out of the boundary layer. The effect of thermophoretic parameter seems to be contrary to the expected norm. We expect the thermophoretic force to ‘push’ the mass away from the surface thereby reducing the concentration in the boundary layer, however, concentration of chemical species is seen to increase in the boundary layer with an increase in the thermophoretic parameter. The use of a heated plate of infinite length increased the concentration of chemical species in the boundary layer. The Biot number which increases and exceeds a value of one for large heated solids immersed in fluids increases the concentration of chemical species for its increasing values.