Thermalcapillary Convection in NaBi(WO₄)₂ Melt

Surface-tension driven flow in NaBi(WO₄)₂ melt is visualized by means of the already proved method of high temperature in situ optical observation. The transition phenomena of the melt from steady spatial to oscillatory behaviour in melt are observed. The oscillatory thermocapillary convection is accompanied by synchronous temperature oscillations with the frequency 10Hz. The onset temperature of thermocapillary convection varies with the change of meniscus curvature of the melt free surface, which probably due to the liquid pressure at the surface associated with the curvature of meniscus. The oscillatory frequency is proportional to the temperature. Finally, another kind of oscillatory thermocapillary convection with the frequency about 5Hz dominating in the undercooled melt is also observed.