DEM investigation on flow regime transition of cylindrical particle in a rotating drum

Abstract A comprehensive understanding of the flow regime transition is a prerequisite for designing and operating the rotating drum, especially when dealing with non-spherical particles. In this study, the multi-sphere method was used to construct cylindrical particles. The optimal number of spherical elements for particles with different aspect ratios was determined in terms of kinetic energy, rotational kinetic energy, collision number, collision force, deformation and angle of repose. And the effects of filling rate, rotational speed and particle size on the macro- and micro-behavior of cylindrical particles were systematically investigated. The results show that when the aspect ratio of cylindrical particle is 2, 3 and 4, the optimal number of spherical elements are 5, 8, and 10, respectively. Four flow structures, namely rolling, cascading, cataracting and centrifuging, were identified with the increase of the rotation speed, but the transition boundary from rolling to cascading is not clear due to the irregular particle shape. Three flow structures, namely slipping, transition, and cascading, were identified with the increase of the filling degree. The transition diagram of flow regime was established. The results show that the aspect ratio has a great influence on the flow transition from slipping to cascading regime. The area covered by the transition flow regime expands as the aspect ratio increases, necessitating a greater filling degree to achieve a stable rolling flow regime.