Flow regimes of cohesionless ellipsoidal particles in a rotating drum

Discrete element method (DEM) has been extensively used in the past to study granular flow in rotating drums, but mainly focussed on spherical particles. Particle shape, as one of the major particle characteristics, can significantly affect the flow behaviour of granular materials. However, how particle shape affects the flow regimes in rotating drums, has not been well studied in the literature. In this work, ellipsoidal shaped particles are used, and its effect on flow regimes is investigated by DEM generated data. The results are analysed in terms of flow regimes, dynamic angle of repose, coordination number (CN) and velocity profiles, showing a good agreement with those reported in literature. The results demonstrate that the typical flow regimes observed for spheres also exist for ellipsoids. However, with increasing rotating speed, ellipsoids transit to the rolling regime later than spheres but earlier to the cascading and cataracting regimes. Similar to spheres, the dynamic angle of repose and mean collision energy increase markedly with the rotating speed, and the mean CN decreases sharply. With aspect ratio of ellipsoids varying from 1.0, the dynamic angle of repose and CN increase, but the mean collision energy decreases at the rotational speed of 5 rpm to 30 rpm. Aspect ratio has a slight impact on the velocity profiles along the mid-chord of the bed. Force analysis indicates that large total force appears mainly near the bed surface, and the force distribution does not vary much with particle shape.