Behavior of particle swarms at low and moderate Reynolds numbers using computational fluid dynamics—Discrete element model

In the present study, the sedimentation of a swarm of mono-sized particles is investigated using the Computational Fluid Dynamics–Discrete Element Model (CFD-DEM) approach. The computational approach employed was able to accurately predict the breakup pattern of the swarm of particles into secondary clusters. The rate of leakage of the particles from the cluster (in the creeping flow regime) was found to linearly increase with an increase in the initial number of particles present in the sedimenting cluster. The breakup pattern of the cluster of particles was found to be highly sensitive to the shape of the outer domain. At Rec = 5, the sedimentation of the cluster in a cylindrical outer domain was observed to break up into six secondary blobs (k = 6), whereas for a square and a rectangular outer domain, the breakup resulted in four (k = 4) and two (k = 2) secondary blobs, respectively. Besides, the CFD-DEM approach was found to be in excellent agreement with the experimental data as opposed to the Oseenlet point particle approach, which could not accurately predict the settling velocities for a sedimenting cluster at a finite Rec and high solid fraction (Rec = 14, ϕs ≈ 0.5).