Shape Dynamics of Interfacial Front in Rotating Cylinders
  The evolution of the interface propagation in a slowly rotating half-filled horizontal cylinder is studied using MRI. Initially, the cylinder contains two axially segregated bands of small and large particles with a sharp interface. The process of the formation of the radial core is clearly captured, and the shape and the velocity of the propagating front are calculated by assuming a one-dimensional diffusion process along the rotation axis of the cylinder and a separation of time scales associated with segregation in the radial and axial directions. We found that the interfacial dynamics are best described when a concentration dependent diffusion process is assumed. 
Gerald H. Ristow and Masami Nakagawa