浮力对环形液池内热毛细对流的影响

EFFECT OF BUOYANCY ON THERMOCAPILLARY CONVECTION IN AN ANNULAR POOL

为了了解浮力的影响,对水平温度梯度作用时环形液池内的热毛细对流进行了非稳态三维数值模拟,环形液池外壁被加热,半径为40 mm,内壁被冷却,半径为20 mm,液池深度为(1-17)mm,流体为0．65cSt的硅油,其Pτ数为6．7．模拟结果表明,当水平温度梯度较小时,流动为轴对称稳态流动,随着温度梯度的增加,流动将会失去其稳定性,在浅液池内,转化为热流体波,浮力对失稳后的流型无影响,但会使热流体波的振幅下降;在深液池内,在常重力条件下,转化成三维稳定流动,在微重力和小重力条件下,转化为三维振荡流动．

In order to understand the effect of buoyancy, we conducted a series of unsteady threedimensional numerical simulations of thermocapillary flow of 0.65cSt silicone oil （Prandtl number Pr =6.7） in an annular pool with different depth （d=1～17 mm） heated from the outer wall （radius r0=40 mm） and cooled at the inner cylinder （ri=20 mm）. The simulation results indicate that the convection is axisymmetric and steady at the small horizontal temperature gradient. But when temperature gradient exceeds some critical value, the convection will undergo a transition to three-dimensional flow. In the shallow thin pool, the hydrothermal wave is dominant and independent of the bouyancy. In the deep pools, the three-dimensional stationary flow appears at the normal gravity and three- dimensional oscillatory flow exhibits at the micro- and low-gravity.