Mixing dynamics of slurry in rotating drum

We study the effects of interstitial fluid viscosity on the rates of dynamical processes in a thin rotating drum half-filled with monodisperse glass beads. The rotating speed is fixed at the rolling regime such that a continuously flowing layer of beads persists at the free surface. While the characteristic speed of a bead in the flowing layer decreases with the fluid viscosity, the mixing rate of the beads is found to increase with the fluid viscosity. These findings are consistent to a simple model related to the thickness of the flowing layer.