CONVECTION IN BINARY-MIXTURES - THE ROLE OF THE CONCENTRATION FIELD

Structure and dynamics of different roll states appearing close to onset of convection in binary mixtures and the influence of the concentration field on the properties of these states are elucidated. Numerical solutions of the hydrodynamic field equations in a vertical cross section perpendicular to the roll axes are reviewed for room temperature ethanol-water parameters. Extended states of stationary overturning convection (SOC) and of traveling wave (TW) convective rolls are investigated as well as spatially confined states of localized traveling wave (LTW) rolls. The field structure and symmetries of these states are discussed. The appearance of a concentration contrast in TW's between rolls of different turning sense is explained. A mean lateral concentration current that is generated in the TW state by the phase difference between the concentration wave and the velocity wave is reviewed. A comparison of LTW's of arbitrary and selected width obtained for different fluid parameters reveals the same field structure under the leading and trailing fronts of these states with only the extensions of the center parts being different. The presence of a large-scale concentration current, the associated large-scale concentration redistribution, and the resulting hindering of the drift of the LTW is reviewed.