Particle subgrid scale modeling in hybrid RANS/LES of turbulent channel flow at low to moderate Reynolds number

Particle dispersion in a periodic channel is studied using the elliptic relaxation hybrid RANS/LES (ER-HRL) model. This approach employs a four-equation linear eddy viscosity (LEV) model while in Reynolds Averaged Navier-Stokes (RANS) mode near the wall, and switches to the LES Smagorinsky dynamic model in the outer flow region. We perform a systematic analysis of the dispersion of six sets of particles having Stokes numbers St = 0.2, 1, 5, 15, 25, 125 at shear Reynolds numbers of Reτ=150, 590. To account for the effect of the unresolved scales on particle dispersion, a novel subgrid-scale model (SGS) is proposed based on the wall-normal RMS of the velocity transport equation. The ER-HRL model is validated against DNS and LES databases, with a globally good agreement. For higher Reynolds number i.e. Reτ = 590, the model, with a much coarser grid, outperforms the LES subgrid stochastic acceleration (LES-SSAM) approach.