Granular material often jam when flowing through an orifice. These photoelastic disks are flowing through an opening in a quasi-2D hopper. Photoelastic material polarize light passing through them if they are squeezed, so you can see by their colorful signature how the particles push on one another and the hopper's walls. They jam at the end of the clip by forming and arch at the opening.
Wow
trustthewater 2 years ago