Drag of an elliptic intruder in a two-dimensional granular environment

TL;DR

This study numerically investigates the drag force on an elliptic intruder in a 2D granular medium, revealing flow and stress field behaviors and proposing a drag law combining yield and dynamic forces.

Contribution

It introduces a numerical analysis of drag on an elliptic intruder in granular media, including a simple collision model and stress field characterization.

Findings

Flow around the intruder resembles perfect fluid streamlines at high drag.

The drag law combines yield force and dynamic term, approximated by a collision model.

Stress fields are well described by the Airy stress function with surface stress data.

Abstract

The drag of an elliptic intruder in a two-dimensional granular environment is numerically studied. The movement parallel to the major axis of the intruder is found to be unstable. The drag law is given by the sum of the yield force and the dynamic term, the latter of which is approximately reproduced by a simple collision model. The flow field around the intruder for sufficiently larger drag force is well fitted by the streamlines obtained from the perfect fluid. The stress fields around the intruder are also investigated when the movement of the intruder is balanced with interactions with the surrounding particles. The Airy stress function is found to well reproduce the stress fields once the stress on the surface of the intruder is given.