Assessing fluidisation quality of cohesive powders using a combined continuum and discrete model

It has long been recognized that powders show four distinct types of behaviour, i.e., cohesive, aeratable, sand-like and spoutable, when fluidised. These effects are believed to be due to the variation in the relative importance of interparticle cohesive forces, such as van der Waals, capillary and electrostatic, compared with the drag force exerted on particles by a fluidising gas. However, such effects are difficult to quantify experimentally due to difficulties in the force measurements. In recent years, the Combined Continuum and Discrete Model (CCDM) has been developed to study flow of particulates where not only interactions between particle and particle but also particle and fluid are important. In CCDM, the continuum gas flow is solved by local averaged Navier-Stokes equations and the discrete solid flow by Newton's second law of motion based on Discrete Element Method with their coupling by Newton's third law of motion. This paper presents a study of the effect of interparticle cohesive forces on gas fluidisation by means of CCDM.