A Novel Discrete Element Model for Collisions of Multiple Wet Particles

The collision of wet granular particles occurs in natural phenomena such as avalanches, erosion, and mudslides, as well as in industrial processes like coated pharmaceutical and fertilizer production. Simulations involving multiple wet particles require a model that captures the kinematics and hydrodynamics without being excessively computationally intensive. A novel discrete element model algorithm is presented here, where the relative motion between each pair of neighboring particles is resolved in a rotating polar coordinate system, considering interactions with other nearby particles. During collision, the thin viscous liquid layer between particles exerts lubrication and capillary forces, which are then used in the dynamical equations for the particles to determine their translational and rotational velocities. Initial results for a system of three wetted spheres exhibit a wide variety of collision outcomes, including agglomeration of all three spheres, separation of all three spheres, and separation of one sphere from the remaining pair. A key parameter is the Stokes number, representing the ratio of particle inertia to viscous forces, with separation versus agglomeration occurring at higher Stokes numbers. A generalized framework of equations for a system of an arbitrary number of spheres has been developed, and additional results will be presented for systems of multiple wet spheres.