Simple Model for Wet Granular Materials with Liquid Clusters

TL;DR

This paper introduces a simple phenomenological model for wet granular materials that captures the transition from liquid bridges to clusters, explaining the non-monotonic shear stress behavior with increasing liquid content.

Contribution

The model accounts for many-particle interactions via liquid clusters and bridges, providing insights into the shear stress maximum in wet granular media.

Findings

Shear stress peaks at an optimal liquid content.

Liquid clusters reduce the liquid-gas interface as content increases.

Model explains transition from pendular to funicular states.

Abstract

We propose a simple phenomenological model for wet granular media to take into account many particle interaction through liquid in the funicular state as well as two-body cohesive force by a liquid bridge in the pendular state. In the wet granular media with small liquid content, liquid forms a bridge at each contact point, which induces two-body cohesive force due to the surface tension. As the liquid content increases, some liquid bridges merge, and more than two grains interact through a single liquid cluster. In our model, the cohesive force acts between the grains connected by a liquid-gas interface. As the liquid content increases, the number of grains that interact through the liquid increases, but the liquid-gas interface may decrease when liquid clusters are formed. Due to this competition, our model shows that the shear stress has a maximum as a function of the liquid-content.