Using the DEM-CFD method to predict Brownian particle deposition in a constricted tube

Modelling of the agglomeration and deposition on a constricted tube collector of colloidal size particles immersed in a liquid is investigated using the discrete element method（DEM）.The ability of this method to represent surface interactions allows the simulation of agglomeration and deposition at the particle scale.The numerical model adopts a mechanistic approach to represent the forces involved in colloidal suspensions by including near-wall drag retardation,surface interaction and Brownian forces.The model is implemented using the commercially available DEM package EDEM 2.3R,so that results can be replicated in a standard and user-friendly framework.The effects of various particle-to-collector size ratios,inlet fluid flow-rates and particle concentrations are examined and it is found that deposition efficiency is strongly dependent on the inter-relation of these parameters.Particle deposition and re-suspension mechanisms have been identified and analyzed thanks to EDEM's post processing capability.One-way coupling with computational fluid dynamics（CFD） is considered and results are compared with a twoway coupling between EDEM 2.3R and FLUENT 12.1R.It is found that two-way coupling requires circa 500% more time than one-way coupling for similar results.