Clogging of soft particles in 2D hoppers

We experimentally study the flow of soft particles through quasi-two-dimensional hoppers. We examine the clogging probability for particles flowing out as a function of the hopper exit width. We find that particle softness plays a critical role in clogging, using different types of particles with varying softness. Clogging is harder for softer particles. The clogging process is caused by the arch formation at the hopper exit. We investigate how the gravitational force, exit width, and particle softness affect the arch size and the number of particles remaining in the hopper when a clog occurs. The experimental results for soft, low-friction, hydrogel particles agree well with previously published simulation data. However, experiments with harder and/or more frictional particles reveal interesting differences.