INFLUENCE OF THE SORET EFFECT ON CONVECTION OF BINARY FLUIDS

Convection in horizontal layers of binary fluids heated from below and in particular the influence of the Soret effect on the bifurcation pr operties of extended stationary and traveling patterns that occur for negative Soret coupling is investigated theoretically. The fixed point s corresponding to these two convection structures are determined for realistic boundary conditions with a many-mode Galerkin scheme for tem perature and concentration and an accurate one-mode truncation of the velocity field. This solution procedure yields the stable and unstable solutions for all stationary and traveling patterns so that complete phase diagrams for the different convection types in typical binary li quid mixtures can easily be computed. Also the transition from weakly to strongly nonlinear states can be analyzed in detail. An investigati on of the concentration current and of the relevance of its constituen ts shows the way for a simplification of the mode representation of te mperature and concentration field as well as for an analytically manag eable few-mode description.