Calibration of a DEM contact model for wet industrial granular materials

TL;DR

This paper develops and calibrates a DEM contact model for wet granular materials, incorporating liquid bridges and migration, validated against experimental flow behavior of powders with different properties.

Contribution

It introduces a framework for calibrating wet contact models using dynamic angle of repose, extending dry models with liquid bridge mechanics and migration effects.

Findings

Model accurately reproduces flow behavior of coarse powders across all liquid contents.

Agreement is limited for fine powders at high liquid contents due to agglomeration.

Dynamic angle of repose is effective for calibration but particle scaling has limitations.

Abstract

This study presents and calibrates a Discrete Element Method (DEM) contact model for wet granular materials in the pendular regime. The model extends a previously calibrated dry contact formulation by incorporating liquid bridges that generate capillary adhesion between particles, while liquid migration is represented through evolving bridge volumes. Two reactor-grade polypropylene powders with different particle size distributions, bulk densities, and surface morphologies are investigated, resulting in distinct wetting behavior. A schematic framework is introduced to relate increasing liquid content to the transition from dry to wet contacts using two key parameters: the minimum liquid film volume and the maximum liquid bridge volume. These parameters are calibrated using dynamic angle of repose measurements from rotating drum experiments. The calibrated model reproduces the experimental flow behavior of both powders: full agreement is obtained for the coarser, more porous powder across all liquid contents, while for the finer, denser powder, agreement is achieved at low to moderate liquid contents. At higher liquid contents, discrepancies arise due to agglomeration effects amplified by particle scaling. These results demonstrate the effectiveness of the dynamic angle of repose as a calibration target and highlight the limitations of particle scaling for strongly cohesive wet granular systems. The proposed framework provides a practical basis for DEM-based modeling of wet powder flow in industrial processes.