液固两相圆柱绕流尾迹内颗粒扩散分布的离散涡数值研究

Numerical Study of Particle Distribution in the Wake of Liquid-Particle Flows Past a Circular Cylinder Using Discrete Vortex Method

基于离散涡方法求得的非定常水流场和颗粒的Lagrange运动方程，数值模拟了稀疏液固两相圆柱绕流尾迹内颗粒的扩散分布．获得了流动的涡谱与3种不同St数颗粒（St=0．25，1．0，4．0）在流场中的分布．通过引入扩散函数来定量表示颗粒在流场中的纵向扩散强度，并计算得到了不同St数颗粒的扩散函数随时间的变化．数值结果揭示出了液固两相圆柱绕流尾迹中的颗粒扩散分布与颗粒的St数和尾涡结构密切相关：1）中小St数（St=0．25．4．0）颗粒在运动过程中不能进入涡核区，而在旋涡结构的外沿聚集，且颗粒的St数愈大，其越远离涡核区域；2）在圆柱绕流尾迹区域内，中小St数（St=0．25．4．0）颗粒的纵向扩散强度随其St数的增大而减小．

Panicle-laden water flows past a circular cylinder are numerically investigated. The Discrete vortex method was employed to evaluate the unsteady water flow fields and a Lagrangian approach was applied for tracldng individual solid particles. A dispersion function was defined to represent the dispersion scale of the particle. The wake vortex patterns, the distributions and the time seties of dispersion functions of particles with different Stokes numbers were obtained. Numerical resuits show that the particle distribution in the wake of the circular cylinder is closely related to the parade＇s Stokes number and the structure of wake vortices： 1 ） the intermediate sized particles with Stokes numbers, St,of 0.25, 1.0 and 4.0 can not enter the vortex cores and concentrate near the peripheries of the vortex structures;2） in the circular cylinder wake, the dispersion intensity of particles decreases as St is increased from 0.25 to 4.0.