环形浅液池内低Prandtl数流体超临界热毛细对流演化

Transition Process of Supercritical Thermocapillary Convection in a Shallow Annular Pool for Low Prandtl Number Fluids

为研究低Prandtl数(Pr)流体热毛细对流演化过程,对环形浅液池内Pr=0.011的流体热毛细对流进行三维数值模拟.研究发现:当Marangoni数较小时,流动为轴对称稳态流动;当Marangoni数超过某一临界值后,流动失稳并转变为热流体波,其波数随Marangoni数增加而减小,而波动主频增大;随着Marangoni数增加,流动加强,沿周向运动的热流体波演变为沿径向运动的径向波,其波数大大减小;当Marangoni数继续增加时,波动频谱曲线噪声增加,呈广谱特性.因此,在计算范围内热毛细对流的演化过程为:轴对称稳态流动-热流体波-单周期径向波-多周期三维振荡流动.

In order to understand the transition process of thermocapillary convection of low Prandtl number（Pr） fluids, a series of three-dimensional numerical simulations on thermocapillary convection of Pr = 0.011 fluid in a shallow annular pool are performed. Results indicate that the flow is axisymmetric steady flow at a small Marangoni number. When Marangoni number exceeds a critical value, the flow destabilizes and bifurcates to the hydrothermal wave. In this case, the wave number decreases and the fundamental frequency increases with the increase of Marangoni number.When Marangoni number continue increasing, the hydrothermal waves are enhanced and bifurcated to the radial waves. During this transition, there exists a sharp drop of the wave number. Finally, the noise on frequency spectrum increases and behaves in multi-frequencies. Therefore, the bifurcation route of thermocapillary convection is from axisymmetric steady flow, hydrothermal wave, radial waves with one frequency to three-dimensional oscillatory flow with multi-frequencies.