Jammed disks of two sizes and weights in a channel: Alternating sequences

Disks of two sizes and weights in alternating sequence are confined to a long and narrow channel. The axis of the channel is horizontal and its plane vertical. The channel is closed off by pistons that freeze jammed microstates out of loose disk configurations subject to moderate pressure, gravity, and random agitations. Disk sizes and channel width are such that under jamming no disk remains loose and all disks touch one wall. We present exact results for the characterization of jammed macrostates including volume and entropy. The rigorous analysis divides the disk sequences of jammed microstates into overlapping tiles from which we construct a small number of species of statistically interacting particles. Jammed macrostates depend on dimensionless control parameters inferred from ratios between measures of expansion work against the pistons, gravitational potential energy, and intensity of random agitations. These control parameters enter the configurational statistics via the activation energies prior to jamming of the particles. The range of disk weights naturally divides into regimes where qualitatively different features come into play. We sketch a path toward generalizations that include random sequences under a modified jamming protocol.

Automated summary

This study explores a sequence of disks with alternating sizes and weights confined to a narrow channel. The results show that under certain conditions, these disks can be jammed into specific states, which can be characterized by a small number of statistically interacting particle species. Furthermore, the study reveals a relationship between the jammed macrostates and control parameters, which are inferred from the ratios between expansion work, gravitational potential energy, and intensity of random agitations against the pistons.