A study on the validity of the multi-sphere Discrete Element Method

Granular materials in industrial applications or nature usually consist of a wide variety of differently formed particles. Very often the shape of the involved objects does not even reveal any symmetry. For the simulation of these particle systems the Discrete Element Method based on spherical or symmetric shaped particles like ellipses/ellipsoids or superquadrics is therefore inadequate. A numerical implementation addressing this problem was found by introducing particles clustered from simpler geometries like spheres. Based on this approach. known as the multi-sphere method. it is possible to ensure computational efficiency for contact detection and force calculation on the one hand, but also allow a suitable representation of shape on the other hand. Today this approach is implemented in several commercial DEM-packages. However, studies on the validity of this approach have only been performed in limited cases. To address this situation. an experimental study performed by Gorham and Kharaz [D.A. Gorham, A.H. Kharaz,The measurement of particle rebound characteristics, Powder Technology 112 (3), 193-202 (2000)] is modeled using the multi-sphere approach. The spherical aluminum oxide particle used in the investigation is approximated by a number of smaller spherical bodies. Macroscopic collision properties are calculated and compared to experimental and numerical results obtained for a rigid spherical particle. (C) 2008 Elsevier B.V. All rights reserved.