Influence of Heat Transfer of Ambient Gas on Oscillatory Flow Transition of Thermocapillary Flow

Thermocapillary flow in a liquid bridge changes from laminar to oscillatory flow with increasing a temperature difference at the free surface. It is considered that the heat transfer at the liquid bridge surface is one of the important parameter to determine the onset of oscillatory flow. The effect of Biot number on the critical Marangoni number was investigated by changing a thermal conductivity of the ambient gas experimentally. The critical Marangoni number was remarkably different from not only the Biot number but also the thermal conductivity of the gas. It was assumed that the transition of oscillatory flow is not organized by the average Biot number and should be considered the local heat transfer at the surface.