Soft particles facilitate flow of rigid particles in a 2-D hopper

We study the flow of binary mixtures of particles in a two-dimensional hopper, mixing rigid plastic spheres with elastic, deformable ones. We explore the transition between jamming and flow based on parameters including the aspect ratio of particle size to hopper channel width, α, the mixing ratio of soft to hard spheres, and the softness of the deformable particles. Previous studies have shown that particles of uniform softness can flow through narrower hoppers, with larger α, than can rigid spheres.¹ In our studies, we measure both the probability of clogging and the components of the arch that forms in a clog. Our results suggest that adding soft particles to rigid ones facilitates flow. We measure the critical ratio of soft particles required to facilitate flow as a function of soft particle size and deformability. We further observe that the arch rarely contains more than one deformable particle.

1. X Hong, M Kohne, M Morrell, H Wang, ER Weeks. “Clogging of soft particles in two-dimensional hoppers,” Phys. Rev. E 96, 062605 (2017).