关键词: 空间浮区;热毛细对流;表面张力;数值模拟;旋转磁场

Abstract: A numerical study of thermo-capillary convection in melting zone under rotating magnetic field was carried out with full floating zone model.The influence of magnetic field intensity was analyzed on flow field and impurity concentration field.The results show that in the absence of the magnetic field, the concentration field and flow field in the melt show a characteristic of three-vortex symmetric oscillations.The temperature field which is mainly determined by diffusion is distributed symmetrically.Under the action of rotating magnetic field, the number of Ma remains unchanged.When the magnetic field intensity B0≤1 mT, the impurity concentration distribution and flow structure in the melt are similar to the case without a magnetic field.Yet the stirring effect of the rotating magnetic field makes the appearance of the melt periodic oscillation in advance.When the Lorenz force is relatively strong, the three-dimensional vibration convection caused by surface tension is well restrained.At B0=5 mT, the circumferential fluctuation is completely suppressed, and both the flow field and concentration field in the melt zone show two dimensional axial symmetrical distributions.The axial inhibition effect and circumferential stirring action on melt flow caused by rotating magnetic field both contribute to the stability of melt flow, the homogeneity of concentration distribution and temperature distribution, which is conducive to the growth of high quality crystals.

Key words: A numerical study of thermo-capillary convection in melting zone under rotating magnetic field was carried out with full floating zone model.The influence of magnetic field intensity was analyzed on flow field and impurity concentration field.The results show that in the absence of the magnetic field, the concentration field and flow field in the melt show a characteristic of three-vortex symmetric oscillations.The temperature field which is mainly determined by diffusion is distributed symmetrically.Under the action of rotating magnetic field, the number of Ma remains unchanged.When the magnetic field intensity B0≤1 mT, the impurity concentration distribution and flow structure in the melt are similar to the case without a magnetic field.Yet the stirring effect of the rotating magnetic field makes the appearance of the melt periodic oscillation in advance.When the Lorenz force is relatively strong, the three-dimensional vibration convection caused by surface tension is well restrained.At B0=5 mT, the circumferential fluctuation is completely suppressed, and both the flow field and concentration field in the melt zone show two dimensional axial symmetrical distributions.The axial inhibition effect and circumferential stirring action on melt flow caused by rotating magnetic field both contribute to the stability of melt flow, the homogeneity of concentration distribution and temperature distribution, which is conducive to the growth of high quality crystals.