Surface tension-driven convection patterns in two liquid layers

Two superposed liquid layers display a variety of convective phenomena that are inaccessible in the traditional system where the upper layer is a gas. We consider several pairs of immiscible liquids. Once the Liquids have bee n selected, the applied temperature difference and the depths of the layers are the only independent control parameters. Using a perfluorinated hydroc arbon and silicone oil system, we have made the first experimental observat ion of convection with the top plate hotter than the bottom plate. Since th e system is stably stratified, this convective flow is solely due to thermo capillary forces. We also have found oscillatory convection at onset in an acetonitrile and n-hexane system heated from below. The experimental observ ations are in reasonable agreement with linear stability analyses. (C) 2000 Elsevier Science B.V. All rights reserved.