A new cognition on oscillatory thermocapillary convection for high Prandtl number fluids

Abstract

A direct numerical simulations on the oscillatory thermocapillary convection in a non-axisymmetric liquid bridge of high Prandtl number fluids under normal gravity has been conducted by using a new method of mass conserving level set method for capturing any micro-scale migrations of free surface. Against the former studies, the oscillatory behaviors of surface flow (the perturbation of velocity, temperature, and free surface) and flow pattern have been quantitatively investigated simultaneously for the first time. The present results show that the instability of thermocapillary convection originates from the oscillations of velocity, temperature, and free surface at the hot corner. The velocity oscillation responds slowly to the temperature oscillation, which are opposite in transfer direction for each other, resulting in the free surface oscillation. The oscillatory thermocapillary convection in the liquid bridge is eventually ex-cited by the coupling effects of these three kinds of oscillations, which discloses clearly the oscillatory mechanism of thermocapillary convection for high Prandtl number fluids.