Abstract:

In order to understand the characteristics of double-diffusive capillary convection in a shallow annular pool with the capillary ratio of -1, a series of three-dimensional numerical simulations were performed. The working fluid is the toluene/n-hexane mixture with the Prandtl number of 5.54 and Lewis number of 25.8. The inner cylinder is maintained at low temperature and solutal concentration while the outer cylinder is fixed at high temperature and solutal concentration. Results indicate that the double-diffusive capillary convection is steady and axisymmetric at a small thermal capillary Reynolds number. With the increase of thermal capillary Reynolds number, the flow will destabilize into unsteady flow. For the aspect ratio of 0.15, the critical thermal Reynolds number is 231.6 and the dimensionless critical frequency is 10.6. When the capillary Reynolds number exceeds the critical value, there orderly appear the two-dimensional and three-dimensional periodical oscillatory convections. Furthermore, periodical oscillatory convection, subcritical unsteady convection and three- dimensional steady convection are discovered with the variation of aspect ratio.

Key words: annular pool, double-diffusive convection, capillary ratio, numerical simulation, heat and mass transfer

摘要：

对毛细力比为-1时环形液池内二元混合溶液的双扩散毛细对流进行了三维数值模拟, 液池内、外壁维持恒定温度和浓度, 工质Prandtl数为5.54, Lewis数为25.8。结果表明, 当温差较小时液池内会出现二维轴对称稳态流动;随着温差的增加, 流动会失稳, 深宽比为0.15时流动失稳的临界热毛细Reynolds数为231.6, 临界频率为10.6;流动失稳后将转变为周期性振荡流动。液池内流体的流动随深宽比的改变将分别出现周期振荡、亚临界非稳态及三维稳态等流动状态。

关键词: 环形液池, 双扩散对流, 毛细比, 数值模拟, 传热传质