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浮区法是一种无坩埚容器接触、生长高质量单晶的重要晶体生长技术。微重力环境下,热毛细对流成为熔体中的主要对流,因此,研究浮区法晶体生长中热毛细对流的不稳定性具有重要意义。本文利用VOF自由表面追踪模型来捕捉自由界面的运动,数值研究了微重力下动态自由界面液桥内热毛细对流特性及温差(△T)对自由界面变形的影响。结果显示,在较强的温差作用下,整个熔区出现三维不稳性的热毛细对流振荡,并且随着温差的增加,振荡强度增强,振荡波数也随之增加;自由界面呈现出冷、热壁面膨胀而中间收缩的“瓶颈”状分布。自由界面变形率随温差先增长较快,后增长较慢。
The Float Zone Method is an important crystal growth technique that contacts and grows high quality single crystals without a crucible container. In the microgravity environment, hot capillary convection becomes the main convection in the melt. Therefore, it is important to study the instability of the convection of hot capillary in the crystal growth of floating zone. In this paper, the VOF free surface tracking model is used to capture the free-boundary motion and the effect of the thermocapillary convection and the temperature difference (ΔT) on the free-boundary deformation are studied numerically. The results show that under the effect of strong temperature difference, the three-dimensional unstable capillary flow convection appears in the whole melting zone, and the oscillation intensity increases and the oscillation wave number increases with the increase of temperature difference. The free interface shows cold and hot Wall expansion and contraction of the “bottleneck ” shaped distribution. The deformation rate of free interface increases rapidly with temperature difference and then grows slowly.