Convection in a saturated Darcy porous medium with an exothermic chemical surface reaction and Soret effect

We consider a saturated Darcy porous medium with an exothermic chemical reaction on the lower boundary. The Dufour effect is neglected, however the influence of the Soret effect is studied. It is found that increasing the Soret coefficient may be either linearly stabilising or destabilising, depending on the boundary parameters and Lewis number. When stationary convection occurs increasing the Soret coefficient has a stabilising effect. A switch from stationary to oscillatory convection occurs at a lower Lewis number for a greater Soret coefficient. Linearised perturbation equations are given and numerical results for the critical Rayleigh number are presented graphically and then discussed.