Large eddy simulation of turbulent particle-laden flows: effects of sub-grid scale fluctuations on dispersion and deposition of particles

Large-eddy and direct numerical simulations (LES/DNS) coupled with Lagrangian particle tracking were performed to study the effects of sub-grid scale (SGS) fluctuations on the dispersion and deposition of particles. A total of eight cases with particle Stokes numbers ranging from St=2 to St=100 with friction Reynolds numbers of Re_τ = 180 and Re_τ = 360 were considered. First, the fluid velocity seen by particles was assumed to be the LES filtered velocity. Then, particle deposition and dispersion with this assumption were compared with direct numerical simulation (DNS) results at the same condition to clarify the effect of SGS fluctuations. Considerable differences in deposition and dispersion of particles were observed, especially for the particles with lower Stokes number and higher friction Reynolds number.

Then, SGS fluctuations were modeled and added to the filtered velocities in the Lagrangian equations of particles. The accuracy of the proposed model was assessed by comparing the LES and DNS results on the particle mean and fluctuating velocity profiles, particle concentration, and particle deposition velocities. The particle deposition velocities for different cases were also validated against the experimental data.