Banding oscillations of non-Brownian particles in a rotating fluid

Abstract

When non-Brownian particles are suspended in a fluid filling a cylindrical tube rotating about a horizontal axis, axially dependent patterns of particle density develop. In many cases, equally spaced axial bands are observed. In this work, we attempt to solve the problem of oscillations between two different banding configurations. Previous work has shown that inertial modes in the fluid are continuously excited by the particles and are responsible for the banding. We derived a one-dimensional linearized model describing the fluid–particle interaction as the source of the oscillatory phenomenon. The model invokes a mechanism of negative feedback between the wave and particle fields, which was modeled in previous work using computer simulations of multiple particles suspended in a moving fluid. It leads to the prediction of the dependence of the temporal period of the oscillations on the particle density and the fluid angular rotation frequency. These predictions were confirmed experimentally.