Application of hydrodynamic lubrication in discrete element method (DEM) simulations of wet bead milling chambers

Fine grinding in wet stirred media mills is a key operation numerous industrial processes. During milling, beads (typically millimetre scale) collide with each other under rapid agitation. These collisions transfer energy into the surrounding medium, feed stream comprising premixed slurry (a suspension of micron-sized particles), leading to reduced particle size. Numerical simulation provides an opportunity gain mechanistic insight by modelling influences media, agitator speed and rheology on breakage. The multiphase nature milling necessitates models that account for both solid feed. Established fluid-particle coupled methods are principle capable doing this, but need resolve large hydrodynamic lubrication forces between near-contacting demands extremely high fluid field resolution, proliferating size cost. To address this challenge, Discrete Element Method (DEM) lab scale mill presented which bead-bead interaction includes pairwise addition frictional contact forces. model accounts effects simplified yet physically well-motivated way, circumventing computational cost fully fluid-resolved model. A systematic calibration against laboratory presented, thereafter good estimation empirical power draw across full range rotation speeds considered viscosities. differences dissipation modes local distribution along chamber examined extreme viscosity condition, revealing most due inter-particle acting tangentially (shearing rolling) while highly energetic (impact torsion), relying free flows inter-bead mobility, relatively unimportant.