Numerical study of ultrafine particles dispersion in the wake of a cylinder

The dynamics of ultrafine particles are strongly dependent to the air flow topology. In this study, the dispersion of carbon nanoparticles in the wake of a cylinder placed in an air flow at Reynolds number of 9300 is numerically investigated. An Eulerian/Lagrangian approach is used to compute the two-phase flow; the carrier phase is predicted through a RANS (Reynolds Averaged Navier-Stokes) model while a particle Lagrangian tracking method provides the trajectory of each nanoparticle. The present numerical investigation allows studying the influence of Brownian and turbulence effects on the nanoparticles dispersion. The main results reveal that (1) The Brownian diffusion tends to concentrate the carbon nanoparticles in the form of a filament at the periphery of the vortices that are generated in the cylinder wake. (2) The turbulence increases the lateral dispersion of the nanoparticles. It disperses them from the edge to the core of the vortices. (3) The highest concentration levels decrease from the near wake of the cylinder to the far wake region while the lateral dispersion increases.