Direct numerical simulations of inertial settling of non-Brownian particles

The dynamics of particles settling at moderate Reynolds number is studied with periodic boundary conditions. The particle Reynolds number ranges from 0.1 to 50, and the solid volume fraction ranges from single sphere to 0.4. Particle-fluid interactions are solved by immersed boundary method and particle-particle interactions are solved by discrete element method. The principal results are the average settling velocity and the structure formation of particles. The average sedimentation velocities of particles for moderate Reynolds number showed deviation from the well-known power law, and the difference keeps on increasing with decrease in solid volume fractions. This deviation is removed by proposing the division of the power law into three regions of Reynolds number for dilute and non-dilute regimes. By analyzing the particle structures, this difference is due to the particle arrangements by the wake interactions at moderate Reynolds number.