声悬浮条件下扇谐振荡液滴的内部流动规律

采用激光片光源照明和高速摄影技术,并使用聚苯乙烯微球作为示踪颗粒,研究了声悬浮条件下二阶和三阶扇谐振荡液滴的内部流场.耦合Level Set方法和标记网格法数值求解了不可压两相流的Navier-Stokes方程,模拟了液滴的扇谐振荡过程中的形态演化及其内部流动状态.数值计算的流场与实验结果吻合很好.对液滴扇谐振荡过程中的内部流速分布进行定量分析,发现流速在液滴中心区域几乎为零并沿液滴自由表面方向逐渐增大.二阶和三阶扇谐振荡的内部流速沿径向分别呈线性和二次函数分布并与理论预测结果相一致.

Internal flow of acoustically levitated water drops during sectorial oscillations

The internal flow of acoustically levitated water drops undergoing the second and third mode sectorial oscillations has been investigated by using laser sheet illumination and high speed video techniques.Polystyrene microspheres are employed as tracer particles for visualizing flow field patterns.A numerical computation based on the Level Set method is accomplished to simulate drop shape evolution and internal flow field by solving incompressible Navier-Stokes equations for two phase flow.The calculated flow fields are in good agreement with experimental observations.The magnitude of fluid velocity is nearly vanishing at the region around drop center,whereas it increases toward the free surface of levitated drop.It is found that the fluid velocity increases as linear and quadratic functions in the radial direction for the second and third mode sectorial oscillations respectively.The calculated fluid velocity distribution is consistent with theoretical prediction.