Coarse graining Euler-Lagrange simulations of cohesive particle fluidization

Although Euler-Lagrange simulations can be performed with millions of particles, particle coarsening where particles are replaced by parcels is necessary for simulation of large particulate and fluid-particle flows. The present study examines coarsening strategies for cohesive particles, where cohesion arises through either van der Waals interaction or liquid bridges between particles. In the latter case, the dynamics of liquid transfer between particles is also taken into account. Strategies based on matching dimensionless overlap, stress and effective coefficient of restitution are shown to lead to same coarse graining rules, while that based on matching the Bond number yields a different set of rules. Test simulations involving fluidization of cohesive particles reveal that the stress-based coarse graining rules provide better approximation of the average slip velocity between the gas and the particles.