The influence of buoyancy on the oscillatory thermocapillary convection with small bond number

Abstract

The mechanism of the onset of oscillatory thermocapillary convection is analysed for a liquid bridge with small Bond number. It shows that the buoyant forces are significant in the internal region, where the direction of local temperature gradient may turn to the direction of gravity in the case of larger Marangoni number, and the oscillatory state will be excited if the instability condition of convection driven by the buoyant force is satisfied, although the thermocapillary convection is primarily driven by the gradient of surface tension. Therefore, the critical state for the onset of the oscillation is probably dependent on several typical parameters such as the Marangoni number. Grashof number, Prandtl number and Bond number, but not by the only Marangoni number. A simplified model is suggested for a silicon oil bridge. The theoretical values of critical Marangoni numbers with the results of experiments on the ground, in the rocket, and the Spacelab on-board the Shuttle. That is, the critical Marangoni number will be larger for the case of smaller Bond number such as the experiments on board the Shuttle. This result is of great benefit to space material processes for the delay of oscillatory state appearance.