Abstract
Large-eddy simulation (LES) coupled with a Lagrangian particle tracking was performed, and the particle deposition and dispersion in turbulent channel flows were investigated. Different test cases with particle Stokes numbers varying from St = 2 to St = 100 were considered in a fully developed turbulent channel flow at a friction Reynolds number of Reτ = 180. The Dynamic Smagorinsky model was used to model the sub-grid scale fluctuations of carrier flow. In the first set of simulations, the effects of sub-grid scale fluctuations in LES were not considered on the Lagrangian particles. Instead, the velocity of carrier flow seen by particles was simply taken as the fluid filtered velocity. Next, direct numerical simulations (DNS) for the same test cases were performed to clarify the importance of sub-grid scale fluctuations seen by the Lagrangian particles. To clarify the differences, the predicted deposition velocities predicted by both LES and DNS methods were compared with the available data in the literature. Deposition velocities predicted by LES were significantly less than those predicted by DNS, especially for the cases with lower particle Stokes numbers. In addition to the deposition velocity, the particle dispersion was also significantly affected by the sub-grid scale fluctuations in the channel. To shed light on differences between particle dispersion for different cases, time and space averaged particle concentrations were evaluated and compared. Finally, the particle mean and fluctuating velocity profiles for different cases were reported.
