Discrete element analysis of normal elastic impact of wet particles
The presence of liquids in particulate materials can have a significant effect on their bulk behaviour during processing and handling. It is well recognised that the bulk behaviour of particulate materials is dominated by the interactions between particles. Therefore, a thorough understanding of particle-particle interaction with the presence of liquids is critical in unravelling complex mechanics and physics of wet particulate materials. In the current study, a discrete element method for wet particulate systems was developed, in which a contact model for interactions with pendular liquid bridges between particles of different sizes was implemented. In order to evaluate the accuracy and robustness of the developed DEM, normal elastic impacts of wet particles with a wall were systematically analysed. It was shown that the DEM simulations can accurately reproduce the experimental observations reported in the literature. In addition, the DEM analysis was also in good agreement with the elastohydrodynamic model. It was further demonstrated that the rebound behaviour of wet particles is dominated by the Stokes number. There was a critical Stokes number, below which the particle will stick with the wall. For impacts with a Stokes number higher than the critical Stokes number, the coefficient of restitution increases as the stokes number increases for elastic particles. It was also found that the contact angle and surface tension played an insignificant role in the normal impact of wet particles, while the viscosity of the liquid presented has a dominant effect on the rebound behaviour.
Keywords: DEM, Wet particles, Liquid bridge, Coefficient of restitution, Normal impact