Large eddy simulation of particle-laden turbulent flow over a backward-facing step

Two-dimensional particle-laden turbulent flow of an air stream carrying small spheres is simulated over a backward-facing step. Simulation of the continuous phase is performed by the method of large eddy simulation while the particle phase is solved by a Lagrangian method. The simulation is carried out with the flow parameters and geometry of the test section the same as those of the experiment carried out by Fessler and Eaton [J. Fluid Mech. 314 (1999) 97]. Predicted mean velocity profiles of the two phases are in good agreement with available experimental results. Simulation of the gas phase provides evolution details of vortical structures of the backward-facing step flow including rolling up, growing, merging and breaking up of vortices. Simulation also predicts the instantaneous concentration distribution of the particles. The effects of particle Stokes number and the initial two-phase velocity slip on particle distributions are further numerically investigated by introducing spheres of different sizes into the channel flow