高雷诺数层流管道中颗粒惯性聚集特性的力学分析

Mechanics analysis on inertial focusing of particles in laminar pipe flow with high reynolds number

根据相对运动原理,结合CFD技术,数值研究了在圆形截面通道高Re数层流中,颗粒所受惯性升力的空间分布特征,提出了颗粒惯性聚集现象在高雷诺数层流管道中所出现的内部聚集圆环的力学成因和影响因素。研究结果表明:颗粒在高雷诺数工况下所受的惯性升力的空间分布规律与低雷诺数工况完全不同,有两个稳定的升力零点:一个靠近通道中心,是形成颗粒内环聚集区域的力学成因;另一个靠近壁面,是形成颗粒外环聚集区的力学成因。这种现象的产生与旋转诱导升力并无明显相关性,而是源于流场压力场的贡献;影响颗粒内环聚集区的主要因素为颗粒相对粒径和Re数。相同条件下,该内环聚集区的半径会随颗粒相对粒径的增大而增大,随管道Re数的增大而减小。

According to the“Principle of Motion Relativity”and combined by CFD technique,the spatial characteristics of the inertial lift force applied on the particles were numerically investigated inside a circular pipe laminar flow with high Reynolds number.The mechanic cause and some impacts were proposed on the inner annulus of focusing particles.The results showed that the spatial characteristics of inertial lift force on the particles inside the laminar pipe flow with high Reynolds number were completely different from those inside the laminar pipe flow with low Reynolds number.There would be two stable zero-lift-force points transversely:one was near the centerline of the pipe,causing the inner annulus of the focusing particles and the other was near the pipe wall,causing the outer annulus of the focusing particles.Instead of from the rotation-induced lift force,the formation of this phenomenon was mainly from the contribution of flow pressure.The main impacts on the inner annulus of the focusing particles were the diameter ratio of particle to pipe and the Reynolds number based on the pipe diameter.The radius of the inner annulus would increase with the increased size of the particles while it would decrease with the increased Reynolds number.