Modeling and analysis of flow regimes in hydraulic conveying of coarse particles

Different flow regimes may take place during hydraulic conveying but are not fully understood. This paper presents a numerical study of the horizontal hydraulic conveying of coarse particles by means of the combined approach of computational fluid dynamics (CFD) for the liquid phase and discrete element method (DEM) for particles. The validity of the model is first verified by comparing the measured and predicted radial profiles of solid volume fraction under different operational conditions. On this basis, the model is used to predict the flow regime transition and the corresponding pressure characteristics as the conveying speed increases keeping a constant feed solid volume fraction. It is observed that the flow regimes transit from the stationary-bed flow, through the moving-bed flow, and finally, to the heterogeneous-suspension flow, which is consistent with the experimental observation in the literature. The numerical results are analyzed in detail in terms of flow and force structures. A new phase diagram in terms of the forces acting on particles is proposed to identify flow regimes and their transition. Based on the simulation data, correlations are formulated to predict the pressure drop of the horizontal hydraulic conveying considered.