Experimental study on Prandtl number dependence of thermocapillary-buoyancy convection in Czochralski configuration with different depths

A series of experiments on thermocapillary-buoyancy convection in Czochralski configuration with different liquid depths have been conducted. Prandtl numbers of the working fluids vary from 10 to 29 and the depth of the liquid pool is between 1.5 mm and 8 mm. Results show that the critical Marangoni number increases with the increase of the liquid pool depth. Prandtl number has a little impact on the critical Marangoni number for the shallow liquid pool, but a significant influence for the deep liquid pool. The flow pattern transits from the concentric multi-rolls to the hydrothermal waves in the shallow liquid pool with the increase of Marangoni number. Furthermore, with the increase of Prandtl number and the liquid pool depth, the hydrothermal waves can be suppressed, and thus the concentric multi-rolls flow pattern is easier to appear. In deep liquid pools, the number of the spokes decreases with the increase of Marangoni number and the liquid pool depth, and the spokes move from the crystal edge to the crucible sidewall. In addition, the radical waves close to the crystal edge have been observed at deep liquid pools and large Marangoni numbers.