Numerical simulation of the flow field and solute segregation in edge-defined film-fed growth

The purpose of this study is to clarify the effect of hydrodynamics and mas s transport on the bubble generation in sapphire shaped crystals. The basic idea is that nucleation of bubbles can be anticipated in places were the g as chemical composition is maximum. Finite elements numerical simulation (F IDAP (TM) software) is used in order to solve the momentum, mass and chemic al species conservation equations in the liquid enclosed in the capillary c hannel and in the liquid meniscus. A parametric study is performed and the effect of the die geometry and of the physical parameters are clarified. It is shown that the main effect is related to the rejection of the gas at th e solid-liquid interface and that forced and thermo-capillary convection ca n explain the experimental observation of the concentration of microbubbles very close to the outer crystal surface in certain cases.