> C. Ruyer-Quil
Thermal and solutal Rayleigh-Benard-Marangoni convection induced by solvent evaporation in polymer solutions
work with F. Doumenc, E. Chenier, B. Trouette, T. Boeck, C. Dang-Vu, B. Guerrier
We start this talk by a description of the instability problem for a base flow which is unsteady. Thereafter we describe different methods to treat such a problem : frozen time, non-normal, nonlinear methods. We then present these approaches on a free convection problem occurring during the drying of plane layers of polymer solutions. Convection may be due to various mechanisms, based on buoyancy or Marangoni effect, of thermal or solutal origin. In this transient flow, the different methods presented predict critical time for convection onset and threshold values for convection. Nonlinear and non-normal methods give similar results, within the uncertainty inherent to any transient problem. This work determines this way the leading mechanisms responsible of free convection in drying polymer solutions. It is shown that, when linear stability indicates the presence of several instability mechanisms, it is necessary to invoke nonlinear arguments to establish which is the leading mechanism.