Oscillatory Patterns and Subdiffusion in Granular Segregation Experiments
by
Stephen W. Morris
University of Toronto
Coauthors: Zeina S. Khan and Wayne A. Tokaruk

Heterogeneous granular mixtures tend to segregate when tumbled in a partially filled, horizontal rotating drum. The dynamical evolution of segregation can, under certain conditions, be oscillatory. Continuum, order parameter-style models of this process posit two coupled fields which oscillate out of phase with one another. Here we examine three candidate fields, the surface concentration, the local streaming angle and the projected concentration of the subsurface core. We find that all these quantities are in phase with one another, in contradiction to a recent order parameter model. We have characterized the axial transport in the tube using narrow pulses as initial conditions. We find that the process is subdiffusive, rather than diffusive as assumed in the models.

Date received: October 6, 2003