声波作用下球形颗粒外声流分布的数值模拟

综合考虑声学边界层内的热损失和黏性损失,建立处于平面驻波声压波节位置二维球形颗粒外声流计算模型,利用分离时间尺度的数值方法对颗粒外声流流场特征进行模拟。将模拟结果与相应的解析解和实验结果对比,验证了数值模拟的可靠性。在此基础上,研究了雷诺数Re和斯特劳哈尔数Sr对球形颗粒声学边界层内二阶声流流场结构、涡流强度及范围的影响规律。结果表明,随Sr和Re增大,声学边界层内的涡流结构尺度呈指数形式减小,其涡流尺度与颗粒直径D和激励频率f成反比,与流体介质运动黏度v成正比;且满足低Sr和高Re的声振系统可形成范围较大、更强烈的声流运动。该数值方法可用于对任意物理模型外声流特性的评估。 

Numerical simulation of acoustic streaming distribution outside spherical particles under the action of sound waves

Considering the heat loss and viscous loss in the acoustic boundary layer,a two-dimensional acoustic streaming calculation model of a spherical particle at the sound pressure node of a plane standing wave is established,and the numerical method of separation time scale is used to simulate the characteristics of the acoustic streaming field outside the particle.The reliability of the numerical simulation is verified by comparing the simulation results with the corresponding analytical solution and experimental results.On this basis,the effects of Reynolds number Re and Strouhal number Sr on the second-order acoustic streaming field structure,vortex intensity and range in the spherical particle acoustic boundary layer are studied.The results show that with the increase of Sr and Re,the scale of the vortex structure in the acoustic boundary layer decreases exponentially,which is inversely proportional to the particle diameter and the excitation frequency,and directly proportional to the kinematic viscosity of the fluid medium,and the acoustic vibration system with low Sr and high Re can form a larger range and stronger acoustic streaming.The numerical method can be used to evaluate the external acoustic streaming characteristics of any physical model.