Dispersion of particles in wall-bounded particle-laden turbulent flows with high wall permeability

Abstract

A series of numerical simulations were performed to investigate the distribution and deposition properties of particles in turbulent flows bounded by permeable walls using the Large Eddy Simulation (LES) with a Lagrangian trajectory approach. The wall permeation speeds were taken from 10−4 to 10−2 of the bulk velocity. The directions of the permeation speed were the same at both walls, and they were inward on one wall but outward on the other wall to reserve the fluid mass. Particles with Stokes number (respecting viscous time scale) around 0.1, 1 and 10 were released in the fully developed turbulent channel flow. The particle–particle interaction and the retroaction from particles to the fluid were neglected. The fluid-phase turbulence statistical properties and particle's transport characteristics by vortexes were then analyzed in details. If the wall permeation exists, the turbulence intensities will be depressed close to the outward permeable wall but increased near the inward permeable wall. Not influenced by the wall permeation, the suspended particles with St+ ∼O(1) tend to accumulate in the less vortical zones away from the wall, while those particles in the flow regions near the outward permeable wall will distribute disregarding of the vorticity. The turbulence structures near the outward permeable wall are found to exert promotional effects on the particle deposition rate, but such effects are different for particles with various Stokes number. A distribution tendency of streamwise streaks for the deposited particles is also found on the wall imposed by the high outward permeation speed and the clustering deposition pattern is more obvious with increasing particle Stokes number.