A Particle-Water Based Model for Water Retention Hysteresis

TL;DR

This paper introduces a particle-water discrete element model that effectively captures water retention hysteresis in granular media by modeling local contact angle dynamics, achieving high correlation with experimental data without fitting parameters.

Contribution

The novel approach models water movement and hysteresis in granular media through local contact angle evolution, without relying on fitting parameters, improving understanding of water retention behavior.

Findings

Achieved correlation coefficients above 82%, mostly above 90%.

Successfully modeled hysteresis in water retention during wetting and drainage cycles.

Demonstrated the importance of contact angle dynamics in water retention hysteresis.

Abstract

A particle-water discrete element based approach to describe water movement in partially saturated granular media is presented and tested. Water potential is governed by both capillary bridges, dominant at low saturations, and the pressure of entrapped air, dominant at high saturations. The approach captures the hysteresis of water retention during wetting and drainage by introducing the local evolution of liquid-solid contact angles at the level of pores and grains. Extensive comparisons against experimental data are presented. While these are made without the involvement of any fitting parameters, the method demonstrates relative high success by achieving a correlation coefficient of at least 82%, and mostly above 90%. For the tested materials with relatively mono-disperse grain size, the hysteresis of water retention during cycles of wetting and drainage has been shown to arise from the dynamics of solid-liquid contact angles as a function of local liquid volume changes.