We propose a continuum description for the axial separation of granular materials in a long rotating drum. The model, operating with two local variables, concentration difference and the dynamic angle of repose, describes both initial transient traveling wave dynamics and long-term segregation of the binary mixture. Segregation proceeds through ultraslow logarithmic coarsening. [S0031-9007(99)0...

A dominant aspect of granular flows is flow in thin surface layers. While an understanding of the dynamics of dry granular surface flow has begun to emerge, the case of flow when air is completely replaced by a liquid is largely unexplored. Experiments were performed using particle tracking velocimetry (PTV) in a quasitwo-dimensional rotating tumbler to measure the velocity field within the flo...

We explore the notion of angle of repose for granular materials. As an illustration, we solve free surface problems for centrifuged granular piles. These have recently been considered as an affordable and simple way to experiment with powders and dust in reduced gravity environments such as on the Moon or on Mars.