Bulldozing an immersed granular material in a confined channel

TL;DR

This paper introduces a reduced-order continuum model for the bulldozing of immersed granular materials in a confined channel, capturing complex interactions among grains, fluid, and walls, validated through experiments.

Contribution

The paper develops a novel coupled thin-film continuum model for immersed granular bulldozing, integrating fluid and granular dynamics with experimental validation.

Findings

Model captures wall friction and viscous stresses effects

Numerical simulations explore different interaction scenarios

Experimental results validate model predictions

Abstract

The motion of an immersed granular material in a channel is characterised by complex interactions among the grains, between the grains and the permeating liquid, and between the grains and the channel walls. Here, we develop a reduced-order continuum model for the bulldozing of an immersed, sedimented granular material by a piston in a channel. In our continuum approach, the granular pile and the overlying fluid layer evolve as a system of coupled thin films. We model the granular phase as a dense, porous, visco-plastic material that experiences Coulomb-like friction with the walls. Conservation of mass and momentum under a thin-film approximation leads to an elliptic equation for the velocity of the grains that is coupled with an evolution equation for the height of the granular pile. We solve our model numerically for a variety of different scenarios to explore the interactions between wall friction, internal viscous-like stresses, and fluid flow above and through the pile. We complement our numerical results with a series of experiments that provide insight into the validity and limitations of the model.