用有限差分法对微重力条件下分离结晶生长中的熔体热毛细对流进行了数值模拟, 熔体的深径比A取1和2, 自由界面无因次宽度B取0.05、0.075和0.1; 得到了分离结晶Bridgman生长过程中熔体热毛细对流的流函数分布和温度分布图, 研究了流型的演变过程和流动的失稳机制. 结果表明: 当Marangoni(Ma)数比较小时, 流动为稳态流动并只存在于自由界面附近, 随着Ma数的增加, 流动增强并逐步向熔体内部扩展, 熔体内部温度分布的非线性性增加, 自由界面速度增大; Ma数超过某一临界值后, 流动转化为非稳态流动; 流动失稳的物理机制是流速的变化和阻力的变化之间存在滞后.
In order to understand the fundamental characteristics of thermocapillary convection in the detached solidification under microgravity, the finite-difference method is used to carry on numerical simulation. The result shows that: when Ma is small, the flow of molten liquid is steady and it only exists near the free surface. And with Ma increasing, the flow is expanded toward the inner part of molten liquid gradually and the velocity of flow on the free surface increases. On the contrary, the flow is unstable when Ma exceeds the critical Ma. The physical mechanism of this unstable thermocapillary convection can be explained as: there is a hysteresis between the variety of the velocity and the variety of the resistance.
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