Jamming patterns of granular flow through a constriction

Abstract

We present a mechanism to control jamming of the flow of hard spheres through a constriction. Jamming patterns of steel balls with uniform (all-large) and mixed (large and small) configurations were studied in a 2D hopper. In the uniform case, the percentage of jamming events versus the count of the hard spheres N showed a three-phase regime characterized by an initial no-jamming phase, a jamming phase with a quadratic increase, and a purely jamming phase. In the mixed case, the percentage of jamming events versus the number ratio R of small to large spheres showed a two-phase regime with a linear increase for low R and a logarithmic decrease for high R. Hence, a control of the jamming condition is achieved by simply changing R. All the experimental results were regenerated using simple-rules and agent-based cellular automata (CA) model, which suggests that the jamming patterns observed are dependent on the occurrence of a few dominant jamming configurations.