Direct numerical simulations of suspension of disk-shaped particles

Abstract

This study investigates the dynamics of disk-shaped particles using direct numerical simulations with the smoothed profile method for rigid particles. These disk-shaped particles are formed by joining the spherical beads and are allowed to settle/sediment in a Newtonian fluid. The concentration effects of the mono-dispersed particles are studied in the Stokes regime, varying the volume fraction (ϕ) from 0.0003 to 0.1. Strong inhomogeneities in the system were noticed, producing multiple peaks in the radial distribution function caused by the orientation preference of particles, while settling. A histogram analysis of the particles' orientation angle suggests that particles prefer horizontal orientation at very low volume fractions and then start orienting vertically with subsequent increase in the volume fraction. Average settling velocity increases initially till volume fraction 0.001, creating a local maxima, and then decreases monotonically following the Richardson–Zaki law. It was also found that velocity fluctuations increased with increasing volume fraction, following the ϕ1/3 trend. These fluctuations are smaller than those of rod-like particles and larger than spherical particles, though the qualitative trend is quite similar.