Large eddy simulation of turbulent gas-solid flows in a vertical channel and evaluation of second-order models

Large eddy simulation (LES) has been used for prediction of the particle-laden turbulent flow in a vertical channel. Calculations were performed at a Reynolds number based on friction velocity and channel half-width of 180. Subgrid-scale stresses in the fluid were closed using the Lagrangian dynamic eddy viscosity model. Particle motion was governed by drag. Particle-particle collisions were neglected and the fluid was not modified by the presence of the particles. Results for a particle density ratio of 2118 are presented in this paper, statistics of the dispersed phase were obtained from the trajectories of 250 000 particles. The simulation results were used to perform an a priori evaluation of closure model assumptions in the two-fluid model of Simonin (1991). In general, there is good agreement between LES results and closure assumptions used for the unknown terms in the particle kinetic stress and fluid-particle covariance transport equations. Turbulent momentum transfer from the fluid in the particle kinetic stress equation is accurately predicted. In the fluid-particle covariance equation the greatest discrepancies in closure of the momentum transfer term occur in the near-wall region, indicating the model used for the fluid turbulent time scale must be improved. Closure models for triple correlation transport of the kinetic stress and fluid-particle covariance are also reasonable.