RANS simulation of pollutant dispersion in atmospheric boundary layer: Application of anisotropic concentration model and diffusivity limiter

Abstract

This study proposes an anisotropic concentration diffusivity model in the Reynolds-averaged Navier-Stokes equations and the Eulerian dispersion model. The proposed model combines models to consider the turbulent anisotropic and near-source limited diffusivity based on generalized gradient-diffusion hypothesis and travel time. The proposed model and conventional isotropic models were applied to predict the pollutant dispersion in an atmospheric boundary layer from an elevated source. The predicted concentration profile and plume half-width were validated with an existing wind tunnel experiment. Both proposed model and the isotropic model using the diffusivity limiter accurately predicted the mean concentration profiles at the central vertical plane. However, the equivalent turbulent Schmidt number in the proposed model were different in each direction. The proposed model predicted counter-gradient turbulent diffusion in the streamwise direction.