热对流稳定性机理研究新方法初探

New method of investigating stability of thermal convection

以由浮力和表面张力引起的方腔内自然对流为研究对象,分析两种驱动力引起的不稳定性对热对流形成的贡献,探求研究热对流稳定性的新方法。利用数值模拟优势,调节相应准则数获得浮力与表面张力共同作用以及各自单独作用下的热流场,并以正交分解法抽出各流场的基本流动模式。通过各流场的速度、涡量以及基本流动模式对比,得到结论基本一致,而利用正交分解法抽出流场的基本流动模式更能清晰地表明各驱动力引起的不稳定对热对流的贡献程度。

A physical and mathematical model based on the Czochlarski crystal growth system was developed. The model was used to study the thermal convection in a cavity of length/height rate of 2 ： 1, and the thermal convection was mainly driven by two forces： buoyancy, described by Grashof number Gr, and surface tension, described by Marangoni number Ma. The main interest of the studies was focused on the contribution of Gr and/or Ma to the formation of flow field. Numerical simulations show that various flow patterns can be obtained with different sets of Gr and Ma. Proper orthogonal decomposition （POD） was applied to investigate the role played by Gr and Ma. POD is a powerful analytic method for the flow structure, with which basic flow modes of any complex flow could be extracted. By comparison of the basic flow modes with other characteristics such as average values and vortices of flow fields caused by Gr and/or Ma, it can be seen that POD can found its important application in analyzing the mechanism of thermal convection.