Naissance de la convection thermo-solutale en couche poreuse infinie avec effet Soret

The onset of Soret-driven convection in an infinite cell filled with a porous medium saturated by a binary fluid is studied. The impermeable horizontal walls are maintained at different and uniform temperatures. For a cell heated from below, the motionless solution loses its stability via a stationary bifurcation when the separation ratio $\text{ψ}$ is higher than a Lewis and normalized porosity dependent value $\text{ψ}{}_0$; for $\text{ψ<ψ}{}_0$, it loses its stability via a Hopf bifurcation. For a cell heated from above, the motionless solution is infinitely linearly stable if $\text{ψ>0}$, while a stationary bifurcation occurs if $\text{ψ<0}$. These results are widely corroborated by direct numerical simulations.