Investigation of convection control under the non-uniform RMF in a liquid bridge

Abstract

Under microgravity, thermocapillary flow becomes the dominant convection in float-zone crystal growth, it may lose stability with increasing Marangoni number, and the convection instability is detrimental to crystal quality. Because of the excellent electrical conductivity of semiconductor melt, the external rotating magnetic field (RMF) is applicable to control melt convection. In a typical simplified float-zone model, the influences of the non-uniform RMF, which is generated by the RMF inductor with three pairs of poles, on the three-dimensional thermocapillary flow are investigated numerically. Our results demonstrate that the axial velocities are reduced under the non-uniform RMF while the melt is stirred in azimuthal direction by RMF, as a result, the three-dimensional convection after the instability becomes to a two-dimensional axisymmetrical flow. It implies that the non-uniform RMF can control melt convection effectively for high-quality crystal growth.