A Numerical Study on Interparticle Collisions in a Microseparator/Classifier by a Macroscopic Particle Model

An effect of feed concentration on particle focusing in an arc microchannel is numerically examined. A macroscopic particle model, which does not need any drag and lift force correlations and hence can be regarded as quasi-direct numerical simulation, is employed to model interparticle collisions due to high shear rates in the microchannel. The model can take into account physical boundaries of particles in contact. In dilute conditions, all particle trajectories formed smooth inward spirals over the transverse plane. In dense flow conditions, the particle trajectories were distorted by collisions, and then the particle focusing declined. It suggests that a particle concentration, which is regarded as dilute in terms of volume concentration, can be regarded as hydraulically dense due to shear-induced particle collisions in a microchannel. It is predicted that the angle between particle-velocity vectors at successive time steps during collision is rather small. The importance of collision mechanism is discussed for the device application to various materials.