Rayleigh–Bénard instability in reactive binary fluids

We study the hydrodynamic stability of reactive, binary fluids in the Bénard geometry, and the Boussinesq approximation, with both the Soret and Dufour effects included. The boundary conditions are rigid, perfectly conducting walls impermeable to mass flow, conditions which are experimentally approachable. For fast reactions, the reactive fluid is less stable against convection than the one-component fluid with the same values of transport and thermodynamic coefficients, due in part to the presence of a ’’chemical boundary layer’’. A slow reaction stabilizes the fluid if the heat of reaction is large and the fluctuations in temperature and concentration relax on the same time scale (gases). When the separation of these two time scales is large (liquids), reaction is always destabilizing. The influence of the Soret and Dufour effects on stability is most pronounced for slow reactions. We provide some interpretations of the role of chemical reactions on hydrodynamic stability.