Hindered Settling Velocity & Structure Formation during Particle Settling by Direct Numerical Simulation

Abstract

Direct numerical simulation is used to study the dynamics of particle settling for Reynolds number from 0.1 to 50 and solid volume fraction from single particle to 0.4. The principle investigations are the effects of Reynolds number and solid volume fraction on average settling velocity, velocity fluctuations and particles structuring during settling. It is observed that average settling velocity deviates from the well-known power law for dilute suspension and moderate range of Reynolds number. Moreover, the increase of velocity fluctuations with domain size saturates and becomes about constant for moderate range of Reynolds numbers in contrast to low Reynolds number in which the fluctuations keep increasing. These behaviors are due to the separated particle pairs which are formed due to inter-particle wake interactions. As the solid volume fraction increases, the smaller inter-particle distances diminish the wake effects and corresponding particle structures.