微重力条件下开口矩形容器的小Pr热毛细对流

Thermocapillary Convection in Low-Prandtl Fluid in an Open Rectangular Cavity Under Microgravity Condition

采用数值方法研究了微重力条件下开口矩形容器内小 Prandtl数镓 (Ga)熔体生长过程中定常热毛细对流 ,讨论了 Re数、几何纵横比 A和侧壁外加温差的相对高度 H对熔体内温度场和流场分布的影响 .计算结果表明 ,热毛细对流对熔体温度分布有明显的影响 ,从而影响着晶体生长过程 .自由面两侧温度差很小 (如 0 .1K)时 ,熔体内温度场将发生变化 ;当温度差增加即 Re数增加时 ,热毛细对流加强 ,对流和扩散相互作用导致温度场分布更加不均匀 .无论多小的 H值 ,若自由面存在温差 ,都会驱动热毛细对流 ;随着 H值增加 ,热毛细对流会扩展到整个熔区 .几何纵横比 A对熔体内温度场和流场也有影响 ,当 A比较大时 ,在固 /液界面附近扩散起主导作用 .

The steady thermocapillary convection of gallium melt with a low Prandtl number in an open rectangular cavity under microgravity condition has been investigated by using finite-difference method.The effect of Reynolds number,aspect ratio A of the cavity and the dimensionless height H of the heating side on the isotherms and streamlines of melt has been discussed.Simulation results show that thermocapillary convection has great influence on the temperature distribution of low Prandtl number melt,and affects the process of crystal growth as well.The temperature field varies even if the temperature difference is only 01K.Increasing the temperature difference or Re number,the flow will be increased to make the distribution of the temperature field nonuniformly.As long as there exists the temperature difference on the free surface,thermocapillary convection will be driven no matter how small H is in this way the temperature distribution near the solid-liquid interface is affected.With H and Re increasing,thermocapillary convection develops in the bulk melt.The aspect ratio A has also an important influence on the temperature and flow field.If A is large,the diffusion would play a main role on the front of solid/ liquid interface.