微尺度稀薄效应下颗粒沉降的格子Boltzmann方法模拟

基于多松弛格子Boltzmann模型，对竖直细长微通道内颗粒自由沉降过程进行模拟，分析气体稀薄效应、初始位置以及颗粒间相互作用对微颗粒沉降特性的影响.研究表明：随Knudsen数增大，微通道内气体稀薄效应增强，颗粒表面气体滑移速度增大，气相流体有效粘度减小，颗粒相同运动状态下受到气体阻力相应减小，颗粒沉降平衡速度明显增大；不同初始位置颗粒沉降过程存在明显差异，初始位置偏离中心线颗粒将发生水平方向位移且呈振荡趋势，最终稳定于中心线平衡位置；在微尺度双颗粒沉降DKT现象过程中，气体稀薄效应影响颗粒运动特性，后颗粒跟随过程明显增长.

Lattice Boltzmann Simulation of Particle Sedimentation Considering Micro-scale Gas Rarefaction Effect

Sedimentation of micro particles in a narrow microchannel was simulated with multiple-relaxation-time lattice Boltzmann model. Influence of gas rarefaction, initial position of particle and interaction between particles on sedimentation process is analyzed. It is found that gas rarefaction effect becomes obvious with increase of Knudsen number. And the effective viscosity of gas is decreased. At the same time, slip velocity on the surface of particle increases and viscosity resistance of particle decreases, which results in an increase of particle equilibrium velocity. For different initial positions of particle, there exists a significant difference in sedimentation process. It reveals that horizontal motion of micro particle exists besides moving in the vertical direction. And the particle has oscillating tendency before stabilizing on the central position in horizontal direction. For DKT phenomenon in microscale, rarefaction effect is obvious on trajectory of particles and the drafting process is prolonged.