Large Eddy Simulations of Particle-Laden Turbulent Channel Flow

A Lattice-Boltzmann based Large-Eddy Simulation (LES) solver is developed to simulate particle-laden turbulent flows. The Smagorinsky model is employed to account for the sub-grid scale stresses. The solver is first assessed for its accuracy in single-phase flows by comparing LES results for a turbulent channel flow with DNS results. Quantitative agreement within 5% of the mean velocity and the turbulent kinetic energy values across the cross-section of the channel, for grid sizes up to 5 times the Kolmogorov length scale, is achieved. Particle-laden flows are then simulated. It is known that when the particle Stokes number is close to unity, particles concentrate near the wall due to turbophoresis. Initial LES show that as the grid size increases, the predicted particle concentration near the wall increases. This is due to the inability of the LES to capture smaller isotropic eddies which cause particle dispersion near the wall. Two methods are adopted to resolve this issue: i) the addition of a random velocity to the filtered LES velocity to mimic random-walk ii) local grid refinement near the wall to capture the smaller eddies. Simulations with the methods show that while they are both capable of addressing the issue, the local refinement is the more robust approach.