Ultrasonic visualization of thermal convective motion in a liquid gallium layer

For low Prandtl number fluids including liquid metals, optical methods cannot be utilized to visualize convective motion, and in this paper the velocity profile in a liquid gallium layer was measured using ultrasonic velocity profiling, UVP. The applicability of the measurement system was confirmed with the rotating flow of liquid gallium and in the natural convection appearing in a glycerol solution layer. The vessel for the liquid gallium layer was optimized for the acoustic properties of liquid gallium. The measured velocity profile shows a cell like convective motion. The spatio-temporal behavior of large-scale convective motion in turbulent convection was observed as a temporal variation of the velocity profile with two kinds of periodic fluctuations of the convection cell.