Properties of 3D arches in a clogged hopper of soft deformable particles.

We study arches that form during clogging in a 3D system of soft hydrogel particles (bulk modulus 10-30 kPa) in water flowing through a square cross-section tube with a circular outlet. The particles are dyed with a fluorescent dye and a laser sheet is used to locate the particles in 3D when the system clogs. The tube's dimensions are 7.62 cm x 7.62 cm x 25.4 cm. The mean particle diameter is 1.46 cm. We vary the total number of particles from 80-125 and the diameter of the outlet from 2-3.5 cm. We measure the clogging probability, and the 3D particle positions in the clog to identify 3D arches. We find that the number of particles in the clogged arch depends on the width of the orifice and the number of particles.