Research On LES Of Turbulent Flow Over A Backward-facing Step And Particle Dispersion In Flow Fields

A general computer code has been developed for large eddy simulation(LES) of turbulent flow over a backward-facing step in a two-dimensinal duct. For LES, the standard Smagorinsky sub-grid scale model and SIMPLER algorithm are applied to wind field simulation of backstep flow. For low Reynolds number, it is shown that the eddy coherent structures evolving in spatially with time increasing were visualized. The change of the reattachment length with different length of the step and different entrance conditions, is also obtained. We also analyse the flow field characteristics with high Reynolds number. And comparison with experiment data is performed.On this base, the particle movement is simulated by orbital method. Based on research of wind field in large-eddy structure, it reveals the movement of particles and their dispersion in large-eddy structure. The study shows that, the dispersion process of small particles is dominated by the large eddy structure. Thus their distribution can trace the large eddy structures spatially. Due to the difference of pressure between the edge and the center of a large eddy structure, particles tend to congregate at the edge of large eddies. In contrast, the distribution of large particles mainly governed by inertia are relatively insensitive to large eddy. With high inflow velocity, large particles keep their motion in the direction of initial momentum.The useful results obtained lay the foundation for research gas-solid interaction under the micro framework.