Effects of centrifugal acceleration on the flows and segregation in vertical Bridgman crystal growth with steady ampoule rotation

The effects of centrifugal acceleration on the flows and segregation in ver tical Bridgman crystal growth with steady ampoule rotation are investigated through numerical simulation. The numerical model is based on the Boussine sq approximation in a rotating frame, and the fluid flow, heat and mass tra nsfer, and the growth interface are solved simultaneously by a robust finit e-volume/Newton method. The growth of gallium-doped germanium (GaGe) in the Grenoble furnace is adopted as an example. The calculated results at small Froude number (Fr much less than 1) are consistent with the previous predi ction (Lan, J. Crystal growth 197 (1999) 983). However, at a high rotation speed or in reduced gravity, where the centrifugal acceleration becomes imp ortant (Fr-l), the results are quite different due to the secondary flow in duced. Since the direction of the induced flow is different from that of th e buoyancy convection due to the concave interface, the flow damping is mor e effective than that due to the Coriolis force alone. More importantly, ra dial segregation can be reversed during the flow transition from one to the other. (C) 2001 Elsevier Science B.V. All rights reserved.