Pattern formation of frictional fingers in a gravitational potential

TL;DR

This paper investigates the formation and alignment of finger-like patterns in a granular-liquid mixture under gravity, combining experiments, analytical modeling, and simulations to understand the underlying mechanisms.

Contribution

It introduces an analytical model explaining finger alignment due to competition between granular stresses and hydrostatic pressure, supported by simulations and pattern analysis.

Findings

Transition from vertical to horizontal finger alignment with tilt angle and density

Analytical model matches experimental and simulation results

Insights into dyke formation patterns in geological contexts

Abstract

Aligned finger structures, with a characteristic width, emerges during the slow drainage of a liquid/granular mixture in a tilted Hele-Shaw cell. A transition from vertical to horizontal alignment of the finger structures is observed as the tilting angle and the granular density are varied. An analytical model is presented, demonstrating that the alignment properties is the result of the competition between fluctuating granular stresses and the hydrostatic pressure. The dynamics is reproduced in simulations. We also show how the system explains patterns made during dyke formations.