Brazil nut effect

This is work of Jin Sun with Francine Battaglia and Shankar Subramaniam at Iowa State to study polydispersity and boundary condition effects on segregation in granular flows. These give rise to the well-known “Brazil nut” phenomenon where shaking a can of nuts causes the larger nuts to rise to the top even though they are heavier. These movies are animations of long simulations (9M timesteps) of a cylindrical domain containing 7600 granular particles.

The large “Brazil nut” particle has a diameter 3x larger and a mass 224x greater than the small particles. The system on the left includes particle-wall friction and the large particle rises to the top after about 30 “shakes” of the system. The system on the right includes no particle-wall friction and the large particle does not rise.