On the effects of subgrid dispersion in large-eddy simulation of particle-laden turbulent channel flow bounded by rough walls*

Particle-laden turbulent flows observed in many engineering and environmental applications are usually bounded by rough walls. In such flows, the wall roughness affects the particle-turbulence interactions by altering the dynamics of the wall-bounded turbulence. The Eulerian-Lagrangian (EL) point-particle approach is a popular computational strategy for the study of such flows, where the dispersed particles are tracked in a Lagrangian manner, and the continuous carrier phase is evolved in the Eulerian frame. In this study, the EL framework is used to perform a large-eddy simulation (LES) of particle-laden turbulent flow bounded by rough walls under dilute suspension conditions. A particular emphasis of this study is on examining the effects of subgrid dispersion modeling on the statistics of the dispersed and carrier phases. The assessment is carried out by considering periodic turbulent channel flow at frictional Reynolds number of 180 with particles of different inertia under the one-way coupled regime and comparing LES results with results from reference direct numerical simulations. To assess the effects of subgrid dispersion while performing LES, three different models are considered, namely, a no-model approach, a random walk model, and an approximate deconvolution model.