Traveling Granular Segregation Patterns in a Long Drum Mixer
Traveling Granular Segregation Patterns in a Long Drum Mixer
Physical Review Letters, 79, 2975 (1997).
Kiam Choo,
T. C. A. Molteno and Stephen W. Morris
Department of Physics,
University of Toronto, 60 St. George St., Toronto, Ontario, Canada M5S 1A7.
Mixtures of granular media often exhibit size segregation along the axis of a partially-filled, horizontal, rotating cylinder. Previous experiments have observed axial bands of segregation that grow from concentration fluctuations and merge in a manner analogous to spinodal decomposition. We have observed that a new dynamical state precedes this effect in certain mixtures: bi-directional traveling waves. By preparing initial conditions, we found that the wave speed decreased with wavelength. Such waves appear to be inconsistent with simple PDE models which are first order in time.
PACS numbers: 46.10.+z,64.75.+g