单个中性球形颗粒在三维方腔中的运动

A neutrally buoyant finite-size spherical particle in three-dimensional lid-driven cavity flow

采用多松弛格子Boltzmann方法模拟了单个中性球形颗粒在三维顶盖驱动方腔流中的运动。考虑了展向弱受限的对称边界和强受限的固壁边界两种情况下初始位置、颗粒大小以及雷诺数的影响。对于展向弱受限的情形,发现颗粒的初始位置显著影响着最终的运动轨迹。根据相图被划分为三个区域:外层稳定区、内层稳定区以及涡中心区域。通过对颗粒受力的分解解释了其在极限环上运动的机理。此外,还详细介绍了球形颗粒在极限环上的顺时针旋转运动。随着雷诺数的增加,颗粒逐渐向外围靠近,不断旋转达到相应的极限环轨迹。对于选定的初始位置,观察到在高雷诺数时大颗粒向外迁移,而在低雷诺数时大颗粒的极限环靠近涡中心。对于展向强受限的情形,极限环与颗粒的初始位置无关。随着雷诺数的增加,除方腔左上角外,极限环轨迹有向外迁移的趋势。最后,随着颗粒尺寸的增大,极限环向方腔内部收缩。

In this paper,the dynamics of a single neutrally buoyant spherical particle in three-dimensional lid-driven cavity flow is simulated by the multiple-relaxation time lattice Boltzmann method.The effects of initial position,particle size and Reynolds number are considered.For the cases with symmetric boundary conditions in the spanwise direction,it is found that the initial position of the particle critically affects its final trajectory.According to the phase diagram,it’s roughly divided into three regions,the outer stable region,the inner stable region and the vortex center region.The mechanisms for the dynamics of particle on the stable limit cycle trajectory are explained by the force decomposition.In addition,a clockwise rotating motion of particle on the limit cycle trajectory is described in detail.With the increase of Reynolds number,the particle gradually approaches to the periphery,continuously rotates to reach the corresponding limit cycle trajectory.For the selected initial position,we observe that large particle migrates outward at higher Reynolds number,while the limit cycle of large particle at lower Reynolds number is close to vortex core.As for the cases of confined solid walls with no-slip boundaries,the limit cycle is independent of the initial positions of the particle.The limit cycle orbit tends to migrate outward with the increases of Reynolds number,except the top left corner of the cavity,and it will shrink if the particle’s size increases.