Studying on the upper limit of the coarse-grained DEM model for simulating mixing processes in a rolling drum with complex wall boundary

Compared with the original Discrete Element Method, the coarse-grained DEM significantly improves simulation efficiency. In CG DEM, the coarse-grained ratio is defined as the diameter of the coarse-grained particle divided by the diameter of the original particle. When the upper limit of coarse-grained ratio is used, the simulation is the most efficient. The upper value for simulating mixing process of spherical fuel particles was determined using a multi-level methodology. The adequacy of the upper value of the coarse-grained ratio was assessed by comparing the mixing characteristics and kinetic prop-erties of the coarse-grained particle systems with those of the original particle systems in a rotating drum with blades. The impact of rotation speed and particle number on the upper value was examined and dis-cussed. It was observed that the kinetic energy increases with an increase in the coarse-grained ratio, lim-iting the efficiency improvement. To ensure kinetic energy conservation, a scaling law for the restitution coefficient was proposed. Combined with the Reduced Particle Stiffness method, the simulation time of the coarse-grained case is only 1/3030 that of the original case (with a particle number of 2.3 million) when the upper limit of the coarse-grained ratio was used (12.0).(c) 2023 Published by Elsevier B.V. on behalf of The Society of Powder Technology Japan. All rights reserved.