Numerical simulation of gas-particle flow in a single-side backward-facing step flow

Particle-laden turbulent flow over a backward-facing step has been investigated by using large eddy simulation for the fluid phase while particle motion is traced by particle track model. Effects of both drag and gravitational forces on particle motion are considered. The simulation is carried out with the flow parameters and geometry of the test section is same as those in the experiment carried out by Fessler and Eaton (J. Fluid Mech. 314 (1999) 97), who measured the two-dimensional flow fields of both phases. Predicted statistical mean properties of the fluid phase with Reynolds number of 18,400 and particle phase with 70 μm copper spheres and 150 μm glass spheres respectively are in good agreement with the experimental results. Simulation also predicts detailed flow fields of both phases and their evolution. Further investigation has been carried out on the dispersion of particles with different Stokes numbers in the turbulent structure of the fluid field. Motion of glass spheres with diameters 2, 20, 50, 100 and 200 μm, respectively, introduced in the fluid field is simulated. The predicted patterns of instantaneous dispersion of particles reveal that the phenomenon of preferential concentration of particles occurs at a certain range of Stokes number. The effects of initial velocity slip between the two phases and the action of gravity on particle dispersion are also investigated.