Abstract
Surface tension driven flows caused by the bidirectional temperature gradients have an important influence in the quality of crystal. In order to understand the characteristics of fluid flow and heat transfer in Czochralski configuration with bidirectional temperature gradients, a series of three-dimensional numerical simulations of the Marangoni-thermocapillary flow of silicon melt were conducted by using the finite-volume method. The temperature gradients are respectively produced by the temperature difference ΔT on the free surface and the constant heat flux q on the bottom of the crucible. Different flow patterns and temperature profiles are found when changing heat flux q at different ΔT. The flow is steady when heat flux q is small and it becomes oscillatory flow when heat flux q exceeds a critical value. The critical conditions and the characteristics of the flows were discussed. Besides, the results show that the increasing heat flux q makes a greater impact on the elevation of the melt temperature, while ΔT makes a greater impact on the instability of the melt. The location of the maximum melt temperature is determined.
