SINOPSIS

A comparative study on fluid flow and heat and mass transfer, induced by Soret-driven thermosolutal convection in a horizontal porous layer subject to constant fluxes of heat, is conducted for the cases where both horizontal boundaries are stress-free or rigid. The problem formulation is based on the Brinkman-extended Darcy model with the Boussinesq approximation, and the governing equations are solved, analytically and numerically, using a finite-difference method. The critical Rayleigh number for the onset of supercritical and subcritical convection is predicted explicitly as a function of the governing parameters. The threshold for oscillatory flows is also predicted, and the stability diagram, defining various convective regimes, is illustrated. As expected, both free and rigid boundaries yield results that are identical to those predicted by the Darcy model when the Darcy number is small enough. For sufficiently large values of the separation parameter φ, the Nusselt and Sherwood numbers corresponding to free and rigid boundaries exhibit asymptotic behaviors. It is also found that, as expected, the flow intensity and heat and mass transfer rates are more affected by thermal diffusion effects in the case of free boundaries in comparison to rigid ones.