Soft particle clogging in 2D hoppers

We study the outflow of soft, low-friction, hydrogel beads from a quasi-2D hopper, examining the probability of clog formation as a function of hopper exit width. Clogging occurs when an arch forms at the hopper exit. Under conditions of low gravity, the largest arches we find contain four particles. By tilting the hopper chamber, we vary the force of gravity driving the flowing bead system. We find that clogging of soft beads requires the hopper exit to be only slightly larger than the bead diameter, and increasing the force driving the beads towards the exit results in a decreased probability of clogging, holding exit width constant. We also investigate the effects of vibration of the entire hopper system and the effects of increased bead friction upon clogging probability.