Viscoplastic rimming flow inside a rotating cylinder

When a small fraction of viscoplastic fluid is placed into a rotating cylinder, steady states can be reached with pool at the bottom of the cylinder and a residual coating elsewhere. Lubrication theory used to model the film thickness builds on previous models by bridging between two asymptotic limits, incorporating both the gravitational force along the cylinder and the hydrostatic pressure gradients. The model predicts steady states are reached after a small number of rotations and allows exploration of drainage when the cylinder comes to a halt. Experiments using a Carbopol suspension provide a suitable comparison to test the thin film theory.