Experimental studies of volatile binary fluids subject to a horizontal temperature gradient

Convection in a binary fluid with a free surface in the presence of evaporation and condensation is a complex and poorly understood problem. In a two-component fluid where one component is more volatile and has a lower surface tension $\sigma $ than the other, the surface tension of the mixture increases as temperature increases due to solutocapillary effects. In contrast, $\sigma $ decreases as temperature increases in a simple fluid due to thermocapillary effects. The dynamics of the flow in $O$(1 mm) layers of dilute water-methanol mixtures driven by a temperature difference of about 10\r{ }C over a horizontal distance of $\sim $5~cm was studied using 2D-2C particle-image velocimetry (PIV). The liquid layers, which are confined in a 1~cm deep rectangular test cell, are studied under both ambient air and in equilibrium with their vapor(s). The experimental data for these binary fluids are compared with numerical simulations.