Numerical simulation of heat transport and fluid flow in directional crystal growth of GaAs

Recent progress in numerical modeling of the transient heat transport and fluid flow in the GTE GaAs space experiment is reported. The vertical gradient freeze crystal growth system is simulated using a simplified axisymmetric finite element model The enthalpy method is used to model the phase change, and numerical solutions are computed on a fixed grid using the CFD code FIDAP. The numerical results suggest that the shape and melt-back position of the melt-crystal interface are greatly affected by the melting history, therefore making it necessary to model the whole melting and solidification process. The simulated interface evolution far the flight experiment predicts a delay of about 25 min for the actual growth to start after the power reduction begins, which is in good agreement with the experiment. Some numerical issues, such as the advantages and limitations of the fixed domain approach, are also discussed.