基于分形理论的驻波声场中颗粒团运动特性数值预测

Numerical prediction of motion behavior of particle agglomerate in standing wave acoustic field based on fractal theory

基于分形理论,建立驻波声场中颗粒团动力学模型,对颗粒团的夹带系数、相位滞后和漂移系数进行数值预测。将预测结果和实验进行对比,二者吻合良好。在此基础上,研究了组成颗粒团的原生颗粒半径、数目以及排列情况对于颗粒团运动特性参数的影响。结果表明,对于由两个原生颗粒组成的颗粒团,原生颗粒半径越接近,颗粒团与等体积球形颗粒运动特性的差异越大;在分形维数一定时,随着原生颗粒数目的增多,颗粒团的夹带系数减小,相位滞后增加,漂移系数先增大后减小,颗粒团与等体积球形颗粒的动力学行为存在显著差异;原生颗粒排列趋于致密时,颗粒团的夹带系数增大,相位滞后减小,漂移系数发生单调变化,与等体积球形颗粒运动特性的差异缩小。

Based on the fractal theory, the model for dynamics of particle agglomerate in standing wave acoustic field was developed, and the entrainment coefficient, phase lag and drift coefficient of the particle agglomerate were numerically predicted. The prediction results were compared with experimental data, and good agreement was shown. On this basis, the influences of the radius, number and packing of the primary particles in the agglomerate on the parameters that characterize the motion behaviors of the agglomerate were investigated. The results show that for the agglomerate formed by two primary particles, the closer the values of primary particle radius, the larger the difference between the motion behaviors of the agglomerate and the volume-equivalent sphere. When the fractal dimension keeps constant, with increasing number of primary particles the entrainment coefficient decreases, the phase lag increases, and the drift coefficient first increases and then decreases, accompanied by the significant difference between dynamic behaviors of the agglomerate and those of the volume-equivalent sphere. As the packing of the primary particles tends to be denser, the entrainment coefficient increases, the phase lag decreases, the drift coefficient changes monotonously, and the difference in motion behaviors between the agglomerate and the volume-equivalent sphere shrinks.