Darcy-Reynolds forces during intrusion into granular-fluid beds

TL;DR

This study experimentally investigates how a sphere intrudes into fluid-saturated granular beds, testing the applicability of Darcy-Reynolds theory across different particle sizes and viscosities, revealing both consistencies and limitations of the theory.

Contribution

The paper provides experimental validation of Darcy-Reynolds theory for granular-fluid intrusion and identifies viscosity ranges where the theory's predictions hold or break down.

Findings

Consistent intruder dynamics with Darcy-Reynolds theory for varied particle sizes.

Experimental results align with the theory for limited viscosity ranges.

For high viscosities, forces decrease contrary to theoretical predictions.

Abstract

We experimentally study intrusion into fluid-saturated granular beds by a free-falling sphere, varying particle size and fluid viscosity. We test our results against Darcy-Reynolds theory, where the deceleration of the sphere is controlled by Reynolds dilatancy and the Darcy flow resistance. We find the observed intruder dynamics are consistent with Darcy-Reynolds theory for varied particle size. We also find that our experimental results for varied viscosity are consistent with Darcy-Reynolds theory, but only for a limited range of the viscosity. For large viscosities, observed forces begin to decrease with increasing viscosity, in contrast with the theoretical prediction.