微通道中颗粒所受惯性升力特性的数值研究

Numerical Investigation on Mechanism for Inertial Lift on Particles in Micro-channel

基于'相对性原理',建立一个描述颗粒准定常运动的数值计算模型,并结合计算流体力学(Computational fluid dynamics,CFD)技术,数值研究在方形截面的微通道内,球形颗粒所受惯性升力的空间分布特征,揭示颗粒的尺寸对这个惯性升力的影响特点。研究结果表明,惯性升力沿通道半径方向呈现出极具规律性的空间分布特征:靠近管轴附近,惯性升力方向朝管道壁面,且随管轴距离的增加,数值上呈现出先增加后减小的趋势;靠近管壁附近,惯性升力方向朝管道轴心,且越靠近管道壁面,其数值将急剧增大。沿通道半径方向上,惯性升力存在唯一的零点位置,这即是颗粒的惯性聚集位置。惯性升力中尽管共同包含着流场黏性应力与压力的贡献,但对颗粒惯性聚集起真正决定性作用的是流场压力的贡献。这些研究成果有助于完善低Re数固-液两相流动中的力学机理,并为颗粒'惯性聚集'现象在今后的商业应用提供有益的理论指导。

Based on the ＇Galileo Principle of Relativity＇, a numerical model is proposed to describe the quasi-stationary motion of a particle in a straight pipe, by which the inertial lift is numerically obtained on the spherical particle inside a straight micro-channel with squared section, combined by computational fluid dynamics（CFD） technique. The spatial distribution of the inertial lift is numerically investigated and the influence on the inertial force is also obtained by the particle＇s diameter. Results indicate, the inertial lift shows an obvious regularity in spatial distribution： it is towards the channel wall in the vicinity of the channel axis with its magnitude increasing firstly to the maximum and then gradually decreasing to zero in radial direction while it is towards the channel axis in the vicinity of the channel wall with its magnitude increasing sharply close to the channel wall. There is a unique position with zero inertial lift in radial direction, which is just the position of ＇Inertial Focus of Particles＇. The inertial force consists of two components, one is the viscous stress, the other is the pressure stress, but the latter is the determinant to ＇Inertial Focus of Particles＇. These results help to perfect the mechanical mechanism on the solid-liquid flow field with low Reynolds number and enhance the further commercial applications of the ＇Inertial Focus of Particles＇.