We present guidelines to estimate the effect of electrostatic repulsion in sedimenting dilute particle suspensions. Our results are based on combined Langevin dynamics and lattice Boltzmann simulations for a range of particle radii, Debye lengths and particle concentrations. They show a simple relationship between the slope $K$ of the sedimentation velocity over the concentration versus the range $chi$ of the electrostatic repulsion normalized by the average particle-particle distance. When $chi to 0$, the particles are too far away from each other to interact electrostatically and $K=6.55$ as predicted by the theory of Batchelor. As $chi$ increases, $K$ likewise increases up to a maximum around $chi=0.5$ and then decreases again to a concentration-dependent constant over the range $chi=0.5-1$, while the particles transition from a disordered gas-like distribution to a liquid-like state with a narrow distribution of the interparticle spacing.
Download