(129d) The Effects of Adding Soft Particles on the Clogging of Rigid Particles in a 2D Hopper

New directions in cosmetics, pharmaceuticals, and even the food industry increasingly require processing of gel beads and other deformable ingredients. While rigid particle flows through hoppers are fairly well understood, clogging of soft particles and in mixtures of soft and rigid particles is an emerging area of interest. We investigate how the addition of soft hydrogel particles affects the clogging of rigid polypropylene spheres in a quasi two-dimensional hopper both experimentally and through numerical simulations. We also study the characteristics of arch formation at the hopper exit and investigate how the span, aspect ratio, inter-particle angle and number of particles in the arch change with the addition of soft particles. We explore the effect of various parameters by controlling particle softness, particle-particle and particle-wall interactions and hopper geometry, and investigate how they affect clogging probability and arch properties. In our experiments, clogging probability exhibits non-monotonic behavior with respect to the fraction of rigid particles in the mixture, due in part to differences in the contacts of the soft and rigid particles with the hopper wall. In cases of mismatch between the soft and rigid particle sizes, quasi-3d effects may also contribute to the non-monotonicity. The results of our simulations and experiments can help inform improved processing of bidisperse granular flows in many industrial and medical applications.