DISCRETE PARTICLE SIMULATION OF AGGLOMERATE IMPACT COALESCENCE

This paper describes computer simulations of pendular state wet agglom erates undergoing pair-wise collisions. The simulation method is based upon a 'soft' discrete particle formulation. Each agglomerate compris ed 1000 primary particles with the interparticle interactions modelled as the combination of the solid-solid contact forces and also the for ces developed at discrete liquid bridges between neighbouring particle s. For the range of collisional velocities implemented, the agglomerat es invariably coalesced. The energy dissipated was associated primaril y with the viscous resistance of the fluid and the interparticle frict ion rather than by liquid bridge bond rupture. The structure of the re sultant coalesced agglomerate was highly disordered and depended on th e impact velocity. As the impact velocity approached zero, the agglome rates behaved like two rigid bodies bonded together. When the impact v elocity was increased, the size of the circumscribing sphere of the co alesced agglomerate decreased and reached a minimum value at a critica l velocity above which an increase in the circumscribing sphere size o ccurred due to extensive flattening. An increase in the viscosity of t he interstitial fluid resulted in an increase in the proportion of ene rgy dissipated by viscous resistance and a decrease in the proportion dissipated due to interparticle friction. An increase in the fluid vis cosity also resulted in an increase in the critical impact velocity at which the size of the circumscribing sphere of the coalesced agglomer ate was a minimum. (C) 1998 Elsevier Science Ltd. All rights reserved.