Computational Fluid Dynamics Simulation of Concentration Distributions from a Point Source in the Urban Street Canyons

Air pollution in big city areas resulting from exhaust emissions is a major urban problem. Often traffic pollution excess controls air pollution management decisions. There are a number of elaborate predictive models of pollutant dispersion and diffusion that address the effects of variable shapes of city buildings on pollutant concentrations, but few are fully validated. This paper presents ventilation behavior in different street canyon configurations. To evaluate dispersion in a model urban street canyon, a series of tests with various street canyon aspect ratios $(B∕H)$ are presented. Physical modeling in wind tunnels and numerical modeling can be used for dispersion simulation when investigating air quality. The flow and dispersion of gases emitted by a point source located between two buildings inside of the urban street canyons were determined by the prognostic model FLUENT using the four differences closure approximation [standard $\kappa \text{-}\epsilon$ , RNG $\kappa \text{-}\epsilon$ , Reynolds-stress, and large eddy simulation (LES)] and Fire Dynamics Simulator, LES methodology. Calculations are compared against fluid modeling in an industrial wind tunnel at Colorado State University. These buildings were arranged in various symmetric configurations with different separation distances and different numbers of surrounding buildings. The objective of this paper was to develop reliable computer models for the bluff body flow and transport of pollutants or chemical and biological agents in urban environments.