On the settling behaviour of polydisperse particle clouds in viscous fluids

We investigate the behaviour of polydisperse particle clouds settling in a viscous fluid by means of numerical simulations. The sedimentation process is described on examples of bidisperse systems as well as fully polydisperse particle systems, pointing out parallels and differences to the monodisperse case. Based on our results we propose a simple formula which gives the maximum velocity of a polydisperse particle cloud settling in a viscous fluid. The proposed formula agrees with our numerical results even in case of systems with high polydispersity.