Three-dimensional particle-resolved direct numerical simulation study of behaviors of a particle settling near a vertical wall

Abstract

Three-dimensional particle-resolved direct numerical simulation based on the multi-direct forcing and Immersed Boundary method is applied to investigate the indirect particle–wall interactions on the behaviors of a particle settling near a vertical wall in a viscous Newtonian fluid. The particle settling in unbounded domain is also simulated for the references of comparison. It is found that the sideways drift and the anomalous rotation are affected by the initial lateral position of the particle relative to the wall. The oscillation of the sedimentation velocity, rotation shifting and the three-dimensional zigzag migration are closely associated with the vortex shedding, depending on the particle terminal Reynolds number. A particle with small solid/fluid density ratio moves in a narrower range compared to a dense particle with the same Reynolds number when it is being drifted away from the wall, but if it is free of wall effect the light particle is to be more influenced by the eventual unsteadiness of its wake. It's interesting to find that the particle–fluid interaction force is also linked closely with the anomalous rotation rate. It can be proved that the particle–fluid interactions are stronger in three-dimensional cases than two-dimensional versions. First, the particle motion in the direction free of limitations is confined in a limited range due to the wall effect. Second, the rotation behavior is stronger in three-dimensional simulations. Third, the particle settling near a wall with large enough Reynolds number reaches an equilibrium stand-away distance away from the wall in three-dimensional simulations.