通气空泡尾部气泡流仿真和特性分析

ON THE NUMERICAL STUDY AND CHARACTERISTIC ANALYSIS OF BUBBLY FLOW CREATED BY VENTILATED CAVITY

基于欧拉-欧拉双流体模型对通气空泡尾部气泡流进行数值仿真,并采用基于多尺寸分组模型的总体平衡方法预估气泡尺寸分布.应用改进后湍流耗散系数计算模型,考虑了气泡体积含量对在湍流作用下气泡扩散现象的影响.基于上述模型对两种试验工况下流场进行了数值仿真.结果表明模型对空泡尾部回流区特性进行了准确预示,在回流区高湍流度作用下气泡迅速破碎成小气泡.并进一步得到试验体尾流区空泡体积分数和速度分布.尾流区水流速度分布保持了流体经过非流线型对称体时产生的尾流分布规律.仿真结果与试验数据相一致,模型适用性得到验证.

Considering the significant influence that the bubbly flow created at the tail of the ventilated cavity makes on the vehicle hydrodynamics and the cavity control mechanism, a Eulerian-Eulerian two-fluid model was proposed for simulation on the bubbly wakes created by ventilated cavity. The population balance approach integrated with Multiple-Size-Group （MUSIG） model was adopted to predict the bubble size distribution. Furthermore, a new model for the turbulence dispersion coefficient was introduced to take into account the effect of void fraction. Based on the simulation model, the characteristics of the multiphase flow field including a vortex mixing area with high void fraction were successfully captured. The bubbles were found to be broken up into small ones right after entrained into the mixing region due to the high turbulence dissipation rate. The void fraction and velocity distribution in the wake were obtained to compare with experimental data. The water velocity in the wake was found to be in accordance with the distribution law in the wake created by single phase flow passing bluff body. The model was validated in predicting the bubbly flow created by ventilated cavity for good agreement with two experimental cases.