Clarification of Marangoni Convection under microgravity conditions for high quality crystal growth

为了提高熔体生长单晶的质量，研究了熔体中的马兰戈尼对流。研究了液桥中马兰戈尼对流随着热致表面张力差驱动力的增大，由二维定常流动向三维定常流动过渡过程的机理。通过对落轴实验和失重实验结果的比较，证明了在失重条件下观察到的超稳定区在微重力条件下消失。由Marangoni对流引起的液桥温度频率可分为稳定型、周期性脉动型、周期性旋转型、准周期型和复周期型。我们推导了温度振荡模式的模型方程。所得方程与实验结果吻合较好。该方程明确了每种温度波动类型的特征。温度波动类型的转变过程取决于液桥的形状和体积和/或重力水平。通过跌落轴引起的重力从1G到微g的阶跃变化，数值研究了固液界面上的局部热流密度。数值计算结果与实验结果吻合较好。这说明数值分析很好地解释了液桥内的传热现象。固液界面上的热流密度分布通常可以用以下无量纲值的组合来解释：由液桥长度、Marangoni数和Prandtl数归一化的位置。通过数值模拟，阐明了长毛细法下残余重力对熔体重力对流的影响。这些结果阐明了熔体中马拉诺尼对流的机制。因此，它们对于提高熔体生长晶体的质量是有用的。少

Marangoni convection in the melt is investigated for improvement of the quality of the single crystal grown from a melt. The Marangoni convection in a liquid bridge was investigated the mechanism of the transition process from two-dimensional steady flow to three-dimensional periodic flow through three-dimensional steady flow with increasing of the driving force of the thermally induced surface tension difference. The comparison of the results of the drop shaft experiments and the normal-gravity experiments cleared that the super steady region that is observed under normal-gravity conditions vanished under micro-gravity conditions. The temperature frequency in a liquid bridge induced by Marangoni convection classified into following types : steady, periodically pulsating, periodically rotating, quasi-periodic, and complex. We derived the model equations for the temperature oscillation patterns. The equations agree well with the experimental results. The equation clarified the features … More of each temperature fluctuation types. The transition process of the temperature fluctuation types depends on the shape and volume of the liquid bridge and/or the gravity level.Local heat flux on the solid-liquid interface was investigated numerically through the step change of the gravity level from 1G to micro-G induced by the drop shaft. The numerical results agree well with the experimental ones. This shows the numerical analysis explains well the heat transfer phenomena in liquid bridges. The heat flux distribution on the solid-liquid interface could be explained commonly by the combination of the following non-dimensional values : the position normalized by the liquid bridge length, Marangoni number and Prandtl number. The numerical simulation clarified the effect of remain gravity on gravity convection in the melt under Long Capillary method.These results clarified the mechanisms of the Maranogni convection in the melt. Therefore they are useful for improvement of the quality of the grown crystal from a melt. Less