CFD study of the gas-particle flow in a horizontal duct: the impact of the solids wall boundary conditions

摘要

The Johnson-Jackson boundary conditions are included in the twoPhaseEulerFoam solver of OpenFOAM-2.2.x in order to consider the wall-friction effect on the movement of particles. A straight conveying line using Johnson-Jackson boundary conditions is simulated. The results show that the particles' velocity at the wall is in better agreement with the experimental results [1], compared to the results of the original solver neglecting wall-friction. However, the model is valid only for a specific adjusted value of the specularity coefficient. Thus, Johnson-Jackson model is revisited based on the work of Li and Benyahia [2], To improve the accuracy of the granular temperature contribution, a new boundary condition, which incorporates sliding and non-sliding collisions, proposed by Schneiderbauer et al. [3], is included in the solver. The velocity profiles of the particles, using the latter boundary conditions, are compared to that of the Johnson-Jackson cases as well as the experimental results. It appears that the boundary conditions of Schneiderbauer et al. [3] yield better agreement with experimental data since these are based on the physical properties and incorporate the coulomb limit to particle-wall collision. Furthermore, based on the experimental study of Sommerfeld and Kussin [1], wall-roughness appears to be an important factor for the transfer of tangential momentum in vertical direction. Accordingly, wall-roughness and shadow effect [4] are studied in order to propose a new model for including wall-roughness in TFM simulations. Finally, the proposed model is implemented in twoPhaseEulerFoam, and the effect of this phenomenon on the particle's velocity profile is studied. The results show that wall-roughness has a strong effect on rebound and redispersion of the particles and accordingly changes the particles' concentration in the section of conveying line significantly.