Projectile interactions in granular impact cratering

TL;DR

This paper investigates how granular media mediate interactions between impacting objects and container boundaries, revealing boundary effects on penetration depth and effective repulsion between objects during impact cratering.

Contribution

It provides new experimental evidence on boundary-mediated interactions in granular impact cratering, highlighting effects of container boundaries and object interactions.

Findings

Bottom boundary influences penetration depth at low drop heights.

Side walls cause less penetration and induce repulsion.

Two balls dropped side-by-side also repel each other.

Abstract

We present evidence for the interactions between a ball and the container boundaries, as well as between two balls, that are mediated by the granular medium during impact cratering. The presence of the bottom boundary affects the final penetration depth only for low drop heights with shallow filling, in which case, surprisingly, the penetration becomes deeper. By contrast the presence of the side wall causes less penetration and also an effective repulsion. Repulsion is also found for two balls dropped side-by-side.