Abstract
We investigate the flow behavior of granular materials composed of polyhedral particles using an in-house code based on polyhedral representation of particle shapes and a rigorous contact detection algorithm. This algorithm is able to distinguish different types of contact (face-face, face-edge, face-vertex, edge-edge, edge-vertex, vertex-vertex). A linear force law based on normal overlaps at the contact points between particles is used and face-face and face-edge contacts are represented by at least three and two contact points, respectively. Furthermore, to reduce the effect of sharp corners and edges, a small Minkowsky radius is added. This approach is applied to simulate the flow behavior in rotating drums in the cascading flow regime. This geometry is extensively applied in industrial processes such as mixing, grinding, and granulation. Nevertheless, the rheology and scaling behavior for aspherical particles has not been investigated on a systematic basis. In fact, most previous studies have concerned either the rolling regime or the flow of spherical particles. In our simulations, we used icosahedral particle shapes and a broad range of the values of rotation speed, drum and particle diameters, and filling heights. We analyzed the evolution of flow variables including both macroscopic and microscopic properties such as the active layer thickness, the shape of free surface in terms of its average slope and the steepest slope, coordination number, forces, and shear rate of the active layer. We show that the flow behavior can be described in terms of a single dimensionless upscaling parameter combining different system parameters. We consider also the effect of particle coarsening on the flow characteristics. Interestingly, our simulations show that wall slip scales with the same upscaling parameter, meaning that wall slip should be treated with the same status as other flow variables.