单气泡沿过热曲面运动的格子Boltzmann模拟

Lattice Boltzmann simulation on motion of single bubble rising along overheated curved surface

基于一般化的插值补充格子Boltzmann方法和直角坐标系下的复合格子Boltzmann相变模型,构建了贴体坐标系下的复合LBM相变模型。利用Laplace定律及气泡在过热液体中的生长过程对该模型进行验证,所得计算结果与Laplace定律、Mikic解析解吻合良好。采用所构建的模型研究了不同Ja下单气泡沿过热曲面运动的运动特性。结果表明:气泡上升过程经历了沿壁面滑移和脱离壁面两个阶段,且Ja越大气泡生长越快,上升速度变化也越快;曲面导致的气泡形变会使得气泡速度变化产生波动,波动频率和幅度与Ja成正相关;气泡并非一直生长变大,其在脱离壁面后,由于受到周围过冷液体冷凝开始变小;气泡对温度场的扰动程度也与Ja成正相关,同时温度场的剧烈变化也反过来影响气泡的生长。

Based on the generalized form of interpolation-supplemented lattice Boltzmann method and the hybrid phase change LBM model in cartesian coordinate system, a hybrid phase change LBM model in body-fitted coordinate system has been proposed. The model was validated by Laplace＇s law and bubble growth in superheated liquid. The predicted results were in good agreement with both Laplace＇s law and Mikic＇s analytical solution. A single bubble rising along a superheated curved surface under different Jacob numbers was then simulated. The results show that during bubble＇s rising process, it slides over the curved surface at the beginning, and then it departs from the surface. The bubble growth rate and rising velocity increase with Jacob number, and the curved surface leads to a significant deformation with fluctuations in both horizontal and vertical velocities. The fluctuating frequency and amplitude are proportional to Jacob number. After departing from the surface, the bubble becomes small due to the condensation of surrounding supercooled liquid. The bubble disturbed temperature field strengthens Jacob number, and the drastic changes of temperature field, in turn, affect the growth of bubble.