MOVING BOUNDARY COMPUTATION OF THE FLOAT-ZONE PROCESS

A computational capability has been developed to predict the free surface shape, heat transfer and meltÐcrystal interface shapes in ßoat-zone processing. A moving boundary, second order, Þnite volume, incompressible NavierÐStokes solver has been developed for the ßuid ßow and heat transfer calculations. The salient features of the approach include solving the dynamic form of the YoungÐLaplace equation for the free surface shape, dynamic remeshing to Þt the free boundary, a ßexible, multiÐblock, grid generation procedure and the enthalpy method to capture the meltÐcrystal and the meltÐfeed interfaces without the need for explicit interface tracking. Important convective heat transfer modes; natural convection and thermocapillary convection have been computed. It is shown that, whereas the overall heat transfer is not substantially a¤ected by convection, the meltÐcrystal interface shape acquires signiÞcant distortion due to the redistribution of the temperature Þeld by the thermocapillary and buoyancy-induced convective mechanisms. It is also demonstrated that the interaction of natural and thermocapillary convection can reduce the meltÐcrystal interface distortion if they act in opposing directions. It is found that the meniscus deformation can cause the height of the zone to increase but the qualitative nature of the meltÐsolid interface shapes are not signiÞcantly a¤ected. Results are compared with literature to validate the predictive capability developed in this work