Numerical study of the particle sedimentation in a viscous fluid using a coupled DEM-IB-CLBM approach

The trajectories of particles corresponding to different principal movement states are determined for the sedimentation of a pair of particles released symmetrically in a long narrow channel. By analysing the trajectories, it is found that particles go through two distinct symmetry breaking phenomena, a sudden lateral migration that leads to asymmetrically moving centres, and (or) a divergent oscillation that leads to a zero phase lag between the fundamental frequencies of oscillating particles. Since particle's lateral movement and natural rotation display a strong coherence of nearly 1.0 over a transitional oscillatory period, the trajectories of particles without rotational degree-of-freedom are then considered to determine the impacts of natural rotation on the principal movement states. It is shown that the lateral migration can still take place even after removing the rotational degree-of-freedom. However, the divergent oscillation disappears, which makes particles move in a steady oblique or horizontal structure and leads to a smaller terminal Reynolds number.