Numerical simulation of particle–particle adhesion by dynamic liquid bridge

Abstract

In powder handling processes treating wet powders (e.g. wet granulation, coating, and drying), a liquid bridge formed between particles is not static but dynamic due to continuous motion of the particles. Therefore, understanding of a particle–particle adhesion by such a dynamic liquid bridge is an important issue. We here conducted a numerical simulation of the particle–particle adhesion by the dynamic pendular liquid bridge. A computational fluid dynamics (CFD) approach with a constrained interpolation profile (CIP) method was applied to simulate a gas–liquid two phase flow, while a particle motion was calculated by taking into account the dynamic liquid bridge. To verify the simulation results, the following verifications were conducted; (i) wetting behavior of a droplet on a curved surface, (ii) static liquid bridge force between two particles, and (iii) rupture behavior of a liquid bridge with free falling of a particle. As a result, validity of the simulation results was confirmed. The particle–particle adhesion through a droplet on a particle surface was then simulated. In particular, effect of a collision velocity on a wet restitution coefficient was investigated. A velocity criterion for the particle adhesion was determined from the simulation results and compared with that estimated from an analytical model proposed by Ennis et al (1991).