ABSTRACT
In particulate DEM large numbers of interacting and potentially interacting bodies are considered. To determine the contact forces, or inter-particle reactions, the series of calculations must rstly identify which particles are contacting, then in a separate series of calculations the actual contact forces are calculated. These two stages are described as the contact detection and contact resolution stages of the analysis respectively (e.g. Hogue (1998)). Both sets of calculation involve predominantly geometrical calculations. The challenge with contact detection is to develop ecient algorithms to keep track of which particles are in contact or likely to come into contact and to form some type of \neighbour list". Contact resolution involves the accurate calculation of the contact geometry and kinematics, typically characterized by the overlap depth/separation and sometimes also relative tangential motion; however, in some cases the overlap area or volume may be considered. A contact constitutive model is then used to calculate the contact forces from this relatively simple description of the contact geometry. The sequence of calculations associated with calculating the contact forces is undoubtedly the most time-consuming aspect of a DEM simulation, Sutmann (2002) estimates that these
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calculations account for 90% of the DEM simulation time. The proportion of the analysis time taken up in contact resolution depends on the packing density of the system; when the void ratio is lower, the number of contacts per particle increases and the proportion of the analysis time taken up with contact resolution also increases.
