Clogging of soft particles in vibrating 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. 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 aperture 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 then investigate the effects of vibration of the entire hopper system, working in a high frequency limit. Vertical vibrations decrease the clogging probability, due to a disruption of clogging arches. Horizontal vibrations increase the clogging probability, due to an effectively smaller slit size.