Radial segregation of binary-sized mixture of ellipsoids in a rotating drum

Rotating drums are widely used in industry for mixing, milling, coating and drying process. Segregation is inevitable when using rotating drum to mix granules differing in size, density or shape. Though size segregation in the rotating drum has received comprehensive studies over the past decades, most of the studies concentrate on spherical particles. In fact, particle shape could also affect size segregation in terms of equilibrium extent of segregation or segregation rate. There have been a few studies in investigating the shape effects on size segregation. However, the understanding of particle shape induced size segregation is still not well addressed in the literature. In this work, discrete element method is employed to study the radial segregation of binary-sized mixtures of ellipsoidal particles in a rotating drum. The segregation patterns for both spheres and ellipsoids are presented. The effects of rotating speed and aspect ratio of ellipsoids on the extent of segregation in the equilibrium state are investigated. As the revolution increases, the segregation pattern becomes increasingly obvious. Coarse particles tend to segregate to the periphery of the bed, whereas fine ones are trapped in the central area. The deviation of aspect ratio from unity, i.e. elongated or platy shape-type, lowers the extent of segregation at the steady state. It could be conjectured that percolation effect is mitigated when aspect ratio varies. Further attempts are made to investigate the effect of rotation speed on the equilibrium extent of segregation. It is found that in rolling or cascading regime, increasing rotating speed could reduce the extent of segregation for both spheres and ellipsoids.