Rigidly connected overlapping spherical particles: a versatile grain model

This paper describes a method to simulate the dynamics of granular systems consisting of irregularly shaped grains. This method is a simplification and partial improvement of a method that has been developed and employed earlier in simulating the toning process in electro-photographic copiers. Here, grains are modeled as rigidly connected overlapping spherical particles. For each grain a bounding sphere around the center-of-mass is known. Therefore, it can efficiently be decided whether two particles intersect and thus exert contact forces upon each other. A second order time stepping algorithm for such grains is given which needs only one evaluation of the interparticle forces in a time step. In a ten grain example system a favorable but poorly understood phenomenon of energy restoration is exemplified.