Soret effect on darcy-brinkman convection in a binary viscoelastic fluid-saturated porous layer

Abstract

A linear and weakly nonlinear stability analyses is performed to study the onset of Darcy-Brinkman double diffusive convection in a binary viscoelastic fluid-saturated porous layer in the presence of the Soret effect. The modified Darcy-Brinkman-Oldroyd model including the time derivative term is employed for the momentum equation. The expressions for stationary, oscillatory, and finite amplitude Rayleigh number are obtained as a function of the governing parameters. There is a competition between the processes of the Soret coefficient, viscoelasticity, thermal diffusion, and solute diffusion that causes the convection to set in through an oscillatory mode rather than a stationary mode. The effects of the Soret parameter, Darcy number, relaxation and retardation parameters, and Darcy-Prandtl number on the stationary, oscillatory, and finite amplitude convection is shown graphically. The weakly nonlinear theory is based on truncated representation of the Fourier series method and is used to find the Nusselt and Sherwood numbers. Further, the transient behavior of the Nusselt and Sherwood numbers is investigated by solving the nonlinear system of ordinary differential equations numerically using the Runge-Kutta method. © 2013 Wiley Periodicals, Inc.