Numerical investigation of the effect of sub-grid scale eddies on the dispersed particles by LES/FDF model

An LES/FDF model was developed by the authors to investigate the SGS effect on the particle motion in the gas-particle two-phase plane wake flow. The simulation results of dispersion rate for different particles were compared with the results without using the FDF model. It was shown that the large eddy structure is the dominant factor influencing the particle diffusion in space for small particles (small Stokes-number particles), but for intermediate or large diameter particles, the influence of the sub-grid scale eddies on the dispersion rate is in the same order as that of the large eddies. The sub-grid scale eddies increase the particle dispersion rate in most time, but sometimes they decrease the dispersion rate. The sub-grid scale particle dispersion rate is decided not only by the intensity of sub-grid scale eddies and the Stokes number of the particles, but also by the large eddy structure of the flow field. For the particles in isotropic turbulence, the dispersion rate decreases as the particle diameter increases.