SR-DEM: an efficient discrete element method framework for particles with surface of revolution

Many granular products have the shape of surface of revolution (SR), typical examples include round pharmaceutical tablets, shelled capsules and M\&M candies. Discrete Element Method (DEM) simulations are often applied to speed up the study of optimized design parameters along with experiments in the particle processing. For this purpose, a novel Surface of Revolution Discrete Element Method (SR-DEM) to simulate granular system with SR particles (i.e. solids of revolution) is developed for this shape family. As surface of revolution is generated by rotating a plane curve around an axis of rotation that lies on the same plane, the shape of any cross section through the axis of rotation remains unchanged because of azimuthal symmetry. Taking advantage of this unique geometry feature, the contact detection and overlap distance evaluation between SR particles can be handled in 2D space for accurate and efficient DEM simulations. In this paper, a node-to-cross-section contact algorithm is proposed to compute the contact force between a pair of SR particles, whereby surface nodes are seeded on the master particle, and cross-section of the slave particle through the axis of rotation is converted into a signed distance field (SDF). Signed distance value of a master node in the slave's cross-section SDF can be used in the contact resolution. The developed SR-DEM code is validated by multiple cases, including particle-wall, particle-particle collisions, static packing of bi-convex tablets and M\&M candies in a cylindrical container, and dynamic angle of repose of these two type of particles in a rotating drum. The numerical results illustrate that the proposed framework is accurate and efficient for the DEM simulation of SR particles.