EXPERIMENTAL-STUDY OF THERMOCAPILLARY CONVECTION ON A LIQUID BRIDGE CONSISTING OF FLUID WITH LOW PRANDTL NUMBER IN A FLOATING HALF-ZONE

A device of mercury liquid bridge of floating half-zone is designed to experimentally explore thermocapillary convection and its instability of a low Prandtl number liquid. Noncontacted diagnostic techniques we re developed to monitor surface flow and surface deformation. The surf ace flow and the influence of a growing surface film (or skin) on the flow were observed. It is shown that the film is a key factor in chang ing the behavior associated with the thermocapillary convection. The e xperiment indicates that the critical Marangoni number should be much higher than that expected by the numerical simulation. The condition a nd process of surface film growth are discussed. The surface oscillati on of the mercury bridge wrapped with ''dirt-film'' was observed, and the characteristics and the frequency associated with this oscillation are given.