Convection and instability of thermocapillary flow in a liquid bridge subject to a non-uniform rotating magnetic field
Convection and instability of thermocapillary flow in a liquid bridge subject to a non-uniform rotating magnetic field
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非均匀旋转磁场作用下液桥中热毛细管流动的对流和不稳定性
DOI：
10.1016/j.icheatmasstransfer.2017.06.014
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发表时间：
2017
影响因子：
7
通讯作者：
Lei Chengwang
中科院分区：
文献类型：
--
作者：
Yao Liping;Zeng Zhong;Zhang Liangqi;Lei Chengwang
本文采用三维液桥的方法，数值研究了外加非均匀旋转磁场对微重力下半导体熔体热毛细流动的影响。在非均匀RMF条件下，对马兰戈尼数（Ma = 15-50）范围内的热毛细流动进行了对流和不稳定性模拟。目前的结果表明，施加外部非均匀RMF可以提高最大切向速度，降低最大轴向速度。因此，在非均匀RMF的作用下，熔体中保持近似轴对称的流动，有利于生长高质量的晶体。进一步研究了不同非均匀RMFs（对应Taylor数Ta = 3.8 × 102 ~ 1.86 × 104和旋转雷诺数Reω= 2.2 × 104）下的热毛细对流，发现当Ma超过临界值时，热毛细对流可能从近似轴对称的稳定流动过渡到周期性振荡流动。临界Ma一般随非均匀RMF强度的增大而增大。
A three-dimensional liquid bridge is considered in this study to numerically investigate the effects of an external non-uniform rotating magnetic field (RMF) on the thermocapillary flow in semiconductor melt under microgravity. Simulations are carried out to examine the convection and instability features of the thermocapillary flow over a range of Marangoni numbers (Ma = 15–50) under a non-uniform RMF. The present results show that applying an external non-uniform RMF enhances the maximum tangential velocity and depresses the maximum axial velocity. As a consequence, an approximately axisymmetric flow is maintained in the melt under the effect of the non-uniform RMF, which is beneficial for growing high quality crystal. Further investigation of the thermocapillary flow subject to different non-uniform RMFs (corresponding to Taylor numbers Ta = 3.8 × 102–1.86 × 104and Rotating Reynolds number Reω= 2.2 × 104) reveals that the thermocapillary convection may undergo a transition from the approximately axisymmetric steady flow to a periodically oscillatory flow for Ma above a critical value. The critical Ma generally increases with the intensity of the non-uniform RMF.