A comparison of two-fluid model, dense discrete particle model and CFD-DEM method for modeling impinging gas-solid flows

Gas-solid flows have been numerically investigated by various multiphase models, none of which is suitable for all the problems encountered in industries. Different multiphase models have been chosen by different researchers to meet their specific requirements; therefore, it is highly desirable to have a comprehensive understanding of the merits and drawbacks of these models. In this study, three existing multiphase models, including a two-fluid model (TFM), a dense discrete particle model (DDPM) and a combined computational fluid dynamics and discrete element model (CFD-DEM) method, are compared by simulating the flow patterns of impinging particle jet in a channel. Depending on the solid concentration used, the particle jets can either merge into a single jet or cross through each other (particle trajectory crossing effect) when they are impinging. The TFM and the DDPM methods have the advantage of less computational demanding compared to the CFD-DEM method, with the cost of more uncertainties. Using the simulation results obtained from the CFD-DEM method as the benchmark data, it was shown that (i) the TFM fails to predict the well-known particle trajectory crossing effect in any cases as in previous studies (Desjardins et al., Journal of Computational Physics 2008, 227, 2514-2539) but can reproduce the merging cases reasonably well; (ii) the DDPM fails to predict the cases where the two particle jets are emerging due to the over-simplified treatment of particle-particle interactions, highlighting the requirement of a proper way to represent the realistic particle-particle interactions and the importance of volume exclusion effect (the particles cannot overlap) in dense gas-solid flows; and (iii) quantitative comparisons show there are major differences between the results predicted by the three models, highlighting the requirement of further improvement of DDPM and TFM. (C) 2014 Elsevier B.V. All rights reserved.