Analysis of radial segregation of granular mixtures in a rotating drum

TL;DR

This study extends a kinematic model to analyze radial segregation in rotating drums, highlighting the roles of grain size and surface properties, and aligns qualitatively with observed segregation patterns.

Contribution

It introduces a model that accounts for size and surface property differences in granular segregation within rotating drums, expanding beyond previous angle of repose assumptions.

Findings

Segregation is influenced by grain size and surface properties.

Model predictions agree qualitatively with experimental observations.

Inconsistencies arise in more complex cases, suggesting areas for model improvement.

Abstract

This paper considers the segregation of a granular mixture in a rotating drum. Extending a recent kinematic model for grain transport on sandpile surfaces to the case of rotating drums, an analysis is presented for radial segregation in the rolling regime, where a thin layer is avalanching down while the rest of the material follows rigid body rotation. We argue that segregation is driven not just by differences in the angle of repose of the species, as has been assumed in earlier investigations, but also by differences in the size and surface properties of the grains. The cases of grains differing only in size (slightly or widely) and only in surface properties are considered, and the predictions are in qualitative agreement with observations. The model yields results inconsistent with the assumptions for more general cases, and we speculate on how this may be corrected.