Transition behavior from steady to oscillatory thermocapillary flow was experimentally studied in a liquid bridge of molten tin under normal gravity. The experimental difficulties such as preventing oxidation of the melt surface and detecting small amplitude of surface temperature fluctuation were successfully solved. The transition was detected by temperature fluctuation measurement of the melt surface and directly proved by a surface flow visualization experiment in which tin-oxide particles pre-mixed with the melt were used as the tracer. Those results are the first experimental evidence for the transition to oscillatory flow in a low Prandtl fluid, which has never observed yet. Significance of a microgravity experiment is quantitatively shown also.
