微重力环状流简化模型中复杂界面流动及流动稳定性分析研究

Czochralski method is the main manufacturing method for bulk single crystals on the ground, and its growth process involves many physical phenomena such as rotating fluid flow, flow oscillation, heat and mass transfer, thermal stresses and magnetic field coupling effect. The simplified annular flow model considers the flow and heat transfer process between the crystal and the crucible. In this project, we will simulate the flow field, temperature field and concentration distribution in the simplified annular flow model utilizing the self-developed program based on the spectral method and the second-order spatial finite volume method. The influence of the liquid interface deformation and disk rotation on the flow oscillation and boundary layer structure will be studied in the simplified annular flow model. The influence of different types of magnetic fields on the melt flow structure and flow strength in the crucible will be researched. The quantitative analysis of the flow unset mechanism in the simplified annular flow model will be performed using the three-dimensional stability analysis program, the effects of aspect ratio, volume ratio, disk rotation and Prandtl number on the critical Reynolds number, instability mode and frequency will be investigated. Dislocation generation in the crystal will be modeled using the Alexander-Haasen model. We will set up the simplified annular flow experimental platform and perform the flow oscillation experiment. Through this research, the theoretical guides for the thermocapillary flow and flow stability experiments under the microgravity environment and the crystal growth on the ground can be provided.

提拉法是地面生长晶体的主要方法，其生长过程涉及到很多物理现象，如旋转流动、流动振荡、传热传质、热应力以及磁场耦合作用等。环状流简化模型考虑晶体与坩埚之间的流动及传热过程。本项目将利用自主发展的谱方法及空间二阶精度有限体积法的大型程序对环状流简化模型中的流场、温度场及浓度场进行模拟。拟研究环状流简化模型中流体界面变形及圆盘旋转对流动振荡及边界层结构的影响。研究不同磁场类型对熔体流动结构、流动强度的影响。利用三维稳定性分析程序对环状流简化模型中流动失稳机制进行定量分析，揭示深宽比、体积比、圆盘旋转和Pr数对临界失稳雷诺数、失稳模态及频率的影响。利用Alexander-Haasen模型对位错产生进行建模。搭建环状流简化模型实验平台，进行流动振荡实验。本研究可以为微重力环境下环状流简化模型的热毛细流动及流动稳定性实验以及地面生长晶体提供理论指导。

本项目利用环状流简化模型来模拟提拉法晶体生长中晶体与坩埚之间的流动及传热过程。利用高精度谱方法及空间二阶精度有限体积法等大型程序对环状流简化模型中的流场、温度场及浓度场进行了模拟和仿真。研究了环状流简化模型中流体界面变形及圆盘旋转对流动振荡及边界层结构的影响。研究了不同磁场类型对熔体流动结构、流动强度的影响。利用三维稳定性分析程序对环状流简化模型中流动失稳机制进行了定量分析，揭示了深宽比、体积比、圆盘旋转和Pr数对临界失稳雷诺数、失稳模态及频率的影响。利用Alexander-Haasen模型对位错产生进行了建模和模拟。通过拟合晶体材料高温压缩实验数据，分析得到了不同温度下对应的应力-应变曲线。.能量分析结果表明，扰动能量主要由粘性耗散、表面张力做功和扰动流与基本流相互作用等构成。对于小Prandtl数(Pr<=0.01)流体，扰动能量主要来自扰动流和基本流相互作用，失稳机制为流体动力学失稳。分析了粘性耗散产生的机制，计算了环状基本流的粘性耗散以及扰动流的粘性耗散。环状基本流的粘性耗散任然为动能转化为热能的主要机制。搭建了环状流简化模型实验平台，进行流动振荡实验。本研究为空间站微重力环境下环状流简化模型的热毛细流动及流动稳定性实验以及地面生长晶体提供了理论指导。今后将结合空间站热毛细对流实验分析流动失稳机制及粘性耗散产生机制。