A rod-rod repulsive interaction force model for granular volume exclusion and nematic ordering

Abstract

Clusters of self-propelled rods have been proven to form nematic alignment states caused by volume exclusion in a high density/packing fraction limit. Most studies for the mechanics of granular particle with volume exclusion either utilize discrete element methods or explicit models such as the hard-sphere models. Here, we model rods as line segments that follow the properties of dipole-like structures and repel like lines of charge. The repulsive forces are calculated using methods from classical electrostatics. A hard-rod-like interaction is found when rods are in contact while soft repulsion occurs as distance is increased between particles. Degenerate cases for the different configurations of the interacting rods are explored. We propose that this method of simulating repulsion is essential in the nematic alignment of shaken granular rods.