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. 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, finding that the addition of vibrations results in decreased clogging probability.  We additionally conduct simulations, which suggest that the decrease in the clogging is controlled by the amplitude of the vibrations rather than the frequency.