Competition of Hexagons and Traveling Rolls in Binary Fluid Convection

Abstract

We describe of experiments to study the patterns in binary fluid convection in ethanolwater mixtures in a large aspect ratio container in the range of parameters in which both the Soret and non‐Boussinesq effects are important. When non‐Boussinesq effects are negligible, convection in these mixtures close to onset occurs in the form of traveling waves. For pure liquids the dependence of fluid properties on temperature is known to give rise to hexagonal convection patterns. In the range of parameters where both effects are important in the mixtures studied here, we have observed coexistence of traveling waves and hexagons (i.e., at values of separation ratio, $\Psi$∼−0.3). For larger values of |$\Psi$|, the hexagons become unstable and a transition to chaotic convection is observed. The patterns and associated bifurcation diagram for these three regimes will be presented, together with the results of other analysis tools.