Granular Rods Fall Faster in Denser Obstacle Fields

Abstract

How does particle shape affect driven transport through obstacle fields? We simulate a dissipative rod falling under gravity through randomly placed fixed obstacles. For sufficiently slender rods, the mean descent speed before trapping decreases, increases, and then decreases again as obstacle density rises, opening a window of densities in which rods fall faster in denser fields. Scaling arguments based on collision rates and rod geometry explain the three regimes and their crossovers. Particle shape can thus reverse the expectation that crowding slows driven transport.

arXiv comment7 pages, 6 figures; 2 ancillary movies. Data and code: https://doi.org/10.5281/zenodo.23181596