Simulation of Sedimentation of Monodisperse and Polydisperse Suspensions

The behaviour of sedimenting monodisperse suspensions is usually deduced from the flux plot, but this approach is not available for polydisperse suspensions. Also, the diversity of velocities, even in monodisperse suspensions, produces a hydrodynamic diffusion that is not taken into account in Kynch’s theory. The rapid improvement in computing power has made simulation an attractive method. Sedimentation of suspensions with many species can be handled easily, and stochastic effects can be included, if desired. We show that two sources of difficulty, generation of a concentration gradient and control of fluctuations in concentration, can be overcome by choosing the controlling concentration as that immediately below the test sphere.