Pattern formation in a rotating suspension of non-Brownian settling particles.

We report band formation and other pattern formation for a settling suspension of uniform non-Brownian particles in a completely filled horizontal rotating cylinder. The system shows a series of sharp pattern changes that are mapped out as a function of the rotation period and suspension viscosity. The experiment suggests that a large number of patterns and rich dynamics result from the interplay among the viscous drag, and gravitational and centrifugal forces.