Collective Effects and Pattern Formation for Directional Locking of Disks Moving Through Obstacle Arrays

TL;DR

This study investigates how disks driven through obstacle arrays exhibit directional locking and pattern formation, revealing complex dynamic phases, effects of obstacle size, and clogging phenomena as disk density varies.

Contribution

It introduces a detailed analysis of directional locking effects and pattern formation in disk systems navigating obstacle arrays, highlighting the influence of obstacle size and density.

Findings

Multiple locking phases occur at certain drive angles.

Increased obstacle size leads to more locking phases.

Higher disk density reduces locking phases due to collisions.

Abstract

We examine directional locking effects in an assembly of disks driven through a square array of obstacles as the angle of drive rotates from zero to ninety degrees. For increasing disk densities, the system exhibits a series of different dynamic patterns along certain locking directions, including one-dimensional or multiple row chain phases and density modulated phases. For non-locking driving directions, the disks form disordered patterns or clusters. When the obstacles are small or far apart, a large number of locking phases appear; however, as the number of disks increases, the number of possible locking phases drops due to the increasing frequency of collisions between the disks and obstacles. For dense arrays or large obstacles, we find an increased clogging effect in which immobile and moving disks coexist.