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上浮气泡与自由表面相互作用的ISPH-FVM耦合方法模拟

SIMULATION ON THE INTERACTION BETWEEN RISING BUBBLES AND FREE SURFACE BY ISPH-FVM COUPLING METHOD

  • 摘要: 上浮气泡与自由表面相互作用的过程涉及复杂的界面拓扑演化, 该过程一直是气泡流研究领域广为关注的问题之一. 为探究上浮气泡与自由表面相互作用动力学行为, 将不可压缩光滑粒子流体动力学(incompressible smooth particle hydrodynamics, ISPH)方法与有限体积法(finite volume method, FVM)相结合提出了一种ISPH-FVM耦合方法. 在ISPH-FVM耦合方法中, 粒子和网格之间的信息交互是通过核近似插值技术实现, 并将连续表面应力模型(continuous surface stress, CSS)引入当前耦合框架中以评估相界面处表面张力效应. 此外, CSS模型通过 FVM 网格上定义的体积分数进行离散和计算, 并且网格上的体积分数是通过网格支持域内ISPH粒子的核近似插值获得的. 随后, 利用ISPH-FVM耦合方法模拟了平衡状态下圆形气泡振荡以及单气泡上升, 并将模拟结果与其他数值方法结果进行比较, 验证了当前耦合方法中表面张力模型的收敛性以及界面追踪的准确性. 为测试ISPH-FVM耦合方法模拟涉及复杂拓扑变化气泡流的性能, 对上浮气泡与自由表面相互作用的动力学行为进行了分析, 并且研究了不同韦伯数(We)以及雷诺数(Re)对气泡与自由表面相互作用的影响. 研究发现, 随着We数增加上浮气泡与自由表面相互作用时界面将发生大的畸变并且产生的夹带液滴数量也相应增加, 然而上浮气泡与自由表面相互作用的过程并没有随Re数的增加而发生明显差别.

     

    Abstract: The interaction between the rising bubble and the free surface involves complex interface topological evolution, which has been one of the problems in the field of bubble flow. To investigate the dynamic behavior of the interaction between rising bubbles and free surface, an ISPH-FVM coupling method is proposed by combining incompressible smooth particle hydrodynamics (ISPH) and finite volume method (FVM). In the ISPH-FVM coupling method, the information exchange between particles and grids is realized by kernel approximation interpolation technique, and the continuous surface stress model (CSS) is introduced into the present coupling algorithm framework to evaluate the surface tension effect at the phase interface. In addition, the CSS model is discretized and calculated by the volume fraction defined on the FVM grid, and the volume fraction on the grid is obtained by kernel approximate interpolation of ISPH particles in the grid support domain. Subsequently, the ISPH-FVM coupling method is used to simulate the oscillation of circular bubble at the equilibrium state and the single bubble rising, the simulation results are compared with other numerical simulation results to verify the convergence of the surface tension model and the accuracy of the interface tracking in the present coupling method. To test the performance of ISPH-FVM coupling method in predicting bubble flow problems involving complex topological changes, the dynamic behavior of the interaction between rising bubbles and free surface is analyzed, and the effects of different weber number (We) and Reynolds number (Re) on the interaction between bubbles and free surface are also studied. The results show that with the increase of We number, the interface will be greatly deformed and distorted when rising bubbles interact with the free surface, and the number of entraining droplets will increase accordingly. However, the evolution of the interface during the collapse of the rising bubble is basically similar and there is no significant difference with the increase of Re number.

     

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