基于OpenFOAM的气泡上升特性数值模拟

OpenFOAM based numerical simulation on rising characteristics of bubbles

基于开源OpenFOAM架构,对气泡的上升速度和形状进行模拟,模拟结果均与试验数据吻合,表明了计算模型能够准确模拟气泡的运动特征。利用经过验证的模型对不同初始直径气泡的上升速度、压力和气泡纵横比随时间的变化规律以及不同Bo数和Mo数对气泡形状的影响进行系统分析和研究发现:气泡上升过程有一定的加速时间,且速度最终趋于某稳定值,但会有很微小幅度的摆动,初始直径越大的气泡最终上升速度越大;气泡内部压力很快达到一个最大值后,随着气泡上升时间的增长而变小,同时刻下直径较大的气泡,其压力也较大;小气泡的变形较小,且当气泡直径大于某值时,最终的纵横比趋于一定;Bo数为O(0)量级以下或Mo数很大(O(8))时气泡为球形几乎不变形,增大Bo数或减小Mo数气泡逐渐产生形变。

The open source software OpenFOAM was applied to simulate the single rising bubble's behavior.At first,the rising speed and shape of the bubble in references were simulated.The results fit well with the experimental data,thus the accuracy of the calculation model was verified.Variation of the rising speed,pressure and aspect ratio of the bubble with different initial diameters against the time,and effect of the Bo number and Mo number on bubble shape were systematically investigated by employing this validated model.The results showed that,the bubble's speed would increase for a while during its rising,and eventually reached a steady value with slight fluctuation.The larger the bubble's initial size,the higher the final speed of itself.Pressure inside the bubble increased to the maximum rapidly at first,and then decreased with the time.At the same moment,the bubble with larger size had higher pressure inside.When the bubble's diameter tended to a certain value,the final aspect ratio turned to constant.When the bubble's Bo number was small(at or lower than O(0)magnitude)or the Mo number was large(at(O(8)magnitude),the bubble was spheric and nearly had no deformation.Enlarging the Bo number or decreasing the Mo number,the bubble's shape gradually changed.