Thermocapillary Convection Instability in Annular Two-Layer System under Various Gravity Levels

Abstract

In order to reveal the impact mechanism of gravity acceleration on thermocapillary convection instability in two-layer system, the flow characteristics of two-layered thermocapillary convection in annular pool under various gravity levels is investigated by 3D numerical simulation, in which the outer and inner walls are differentially heated. The interface of fluids is assumed to be a flat non-deformable interface, where thermocapillary forces act on. The computational results show that, with the increase of gravitational acceleration the convective structure of the upper layer changes from multi-cell structure to singe cell structure, then to multi-cell structure; while in the lower layer the flow changes from multi-cell to single cell structure. The convection instability mode also is modified, and the wave number at the interface decreases from seven to six. The average oscillatory amplitude of azimuthal velocity decreases with the increase of gravitational acceleration.