发布时间：2022-08-18

文章标题：【学术成果】一篇通讯作者文章在国际学术期刊 Int J Multiphase Flow 上发表

内容：

一颗小石子如何翻越大障碍？我们给出了涡角度的诠释和新的准则数~

 

Li M, Liu HH, Zhang Y. Two-dimensional characterization of particle entrainment over a downstream obstacle. International Journal of Multiphase Flow, 2022. 10.1016/j.ijmultiphaseflow.2022.104228

This study conducts a two-dimensional numerical investigation of the particle entrainment in the presence of a large downstream circular obstacle, and aims to deepen the understanding of the entrainment mechanism and propose a dimensionless number to describe the entrainment threshold. With the coupled lattice Boltzmann and discrete element method, direct numerical simulations are conducted for a wide range of obstacle-to-particle radius ratios (2<Ro/Rp<8) and Reynolds numbers (38≤Re≤160). The results show that the low-pressure separated vortex due to the obstacle is the fluid structure to entrain the particle by vortex stretching at low Ro/Rp (2<Ro/Rp<3.8). Based on this mechanism, a dimensionless number defined as the ratio of the vertical drag force to the particle gravity is proposed, which can be understood as a generalized Shields number including the additional effect of the obstacle radius, and it approaches the constant value of 2.5198 at the critical conditions of entrainment. In addition, we find that at high Ro/Rp (5.6≤Ro/Rp≤8.0), the particle is too far from the separated vortex to undergo sufficient vertical drag force, and thus its inertia should be small enough to ensure the entrainment. In this situation, the entrainment threshold is well described by the Stokes number, which approaches the constant value of 0.2134. At the moderate Ro/Rp (3.8≤Ro/Rp≤5.6) the drag force of separated vortex and the low particle inertia are both essential to realize the particle entrainment.