Convection mixte d'un mélange binaire en milieu poreux

We study the nature of the instability of a binary mixture in a porous medium heated from below in the presence of an horizontal flow. The asymptotic response of the system to a localized perturbation in the both directions of the horizontal plane is evaluated. At the threshold of absolute instability, the rotational symmetry is broken by the presence of the horizontal flow and among infinity of unstable spatio–temporal modes, the system selects the traveling waves which propagate in the flow direction. We also show that in binary mixtures, contrary to pure fluids, the flow may suppress the transition from convective to absolute instability.