A 3D numerical model for flow profiles in a Bridgman tube — The effects of constant and periodic off axis orientation in a low gravity environment

A 3D numerical calculation is performed on a model that depicts the flow profiles due to thermo-solutal convection in a cylindrical tube. The calculations were done with the purpose of delineating the qualitative features of the flow profiles for the cases when the container's axis is perfectly aligned with respect to the mean gravity vector and also when it changes periodically with respect to the gravity vector. It is found that the flow profiles are similar to those of the Rayleigh-Bénard problem in the case of perfect alignment while a swirling pattern appears when the tube's axis is not aligned with the gravity vector. This indicates that it might be preferable to have a slight tilt in the container axis during crystal growth as swirling flow will diminish axial mixing. The solutal convection is the dominant feature of the flow and is affected considerably by the gravity level.