Drag Law of Two Dimensional Granular Fluids

TL;DR

This study investigates the drag force on a disk in a 2D granular medium, revealing fluid-like behavior and the effects of friction and jamming on the force laws through DEM simulations.

Contribution

It demonstrates that drag force in 2D granular media can be modeled by a perfect fluid and identifies the impact of dry friction and jamming on force divergence.

Findings

Drag force can be modeled by a perfect fluid in certain conditions.

Dry friction introduces a yield force independent of speed.

Both yield and drag forces diverge at the jamming point.

Abstract

The drag force law acting on a moving circular disk in a two-dimensional granular medium is analyzed based on the discrete element method (DEM). It is remarkable that the drag force on the moving disk in moderate dense and pure two-dimensional granular medium can be well reproduced by a perfect fluid with separation from the surface of the tracer. A yield force, being independent of the moving speed of the disk, appears if a dry friction between the granular disks and the bottom plate exists. The perfect fluidity is violated in this case. The yield force and the drag force diverge at the jamming point.