Fundamentals Keynote-Investigation of Wet Particle Contact Mechanics

Many industrial applications and natural phenomena consist of mixtures of granular materials and liquids. The inclusion of the liquid forces creates complex contact dynamics. Our understanding of the effect of the liquid is still limited and accurate modelling of these systems is a challenge. In this study, we consider particles coated in thin layers of viscous fluids such that the capillary number is high and viscous forces dominate.

Various models have been proposed to characterise the contact mechanics for particles coated in viscous liquids. Although all based on viscous flow, these models introduce quite different approximations to yield a computationally viable model. Here we present a detailed comparison of the different models with experimental measurements. High-speed imaging and a novel electrical conduction measurement are used to experimentally investigate the particle collision dynamics for linear and oblique collisions. We find that the models can predict the collision outcomes accurately, however they require the inclusion of an empirically fitted, non-physical parameter. It appears that this parameter arises from an overestimate of the viscous forces estimated by the models. The talk concludes with some suggestions regarding how the viscous force models could be improved to better replicate the experimental results.