Particle scale investigation of flow and mixing of wet particles in rotating drums

Granular flow in rotating drums exhibits complex phenomena which are further complicated by the presence of liquids. This paper reviews our recent work on flow of wet particles in rotating drums based on the discrete element method (DEM) simulations. The DEM model was validated by comparing the simulation results with experimental measurements. Particle flow at quasi-static and dynamic states was investigated. In the quasi-static state with the drum rotating at low speeds, wet particle bed failed through avalanche and slow structural change was identified prior to the avalanches. In the dynamic state, flow transited from continuous to avalanche flow with increasing liquid surface tension and a plug flow was developed on the bed surface. Particle mixing in both transverse and axial directions was studied. While cohesion in general reduced transverse mixing, enhanced mixing of wet particles was also observed, which was explained by a theory based on particle circulation period. On the other hand, the axial mixing was well described by Fick s law of diffusion and particle diffusivity decreased with increasing cohesion. A correlation was observed between particle diffusivity and granular temperature.