An overlappable coarsening strategy for discrete element method simulations of bi-disperse granular flows

The coarsening strategy provides a promising avenue for industrial applications of the discrete element method by profoundly reducing computational costs. However, its application in multi-particle-size systems often results in underestimations of the packing solid volume fraction when employing different coarsening ratios. To address this issue, we propose a novel overlappable coarse-grained model specifically designed for bi-disperse systems. In this model, particles are allowed to overlap to a certain extent without experiencing collision forces, with the degree of overlapping described by an overlapping coefficient. This coefficient is determined through fitting discrete element method simulation of bi-disperse packings. Posterior analyses reveal that the traditional coarse- grained discrete element method significantly underpredicts the packing solid volume fraction and consequently the segregation behavior. In contrast, our proposed overlappable coarsening strategy accurately predicts both the packing solid volume fraction and segregation behavior when employing the fitted overlapping coefficient.