Numerical simulation of pollutant flow and dispersion in different street layouts

The objective was to simulate the pollutant emissions from vehicle exhausts in a street canyon and to investigate the impact of street canyon geometry including canyon height to width ratio (h/w) and relative height (h₂/h₁) to the flow structure and air pollutant dispersion. The paper reports work on 15 canyon cases, when the validation of the numerical model was evaluated using an extensive wind tunnel experiment (Kastner-Klein and Plate). We found the modified RNG k-ε turbulence model to be the optimum model. The pollutant transport and diffusion greatly depends on the street canyon configuration and the type of flow regimes inside the canyon. We calculated the retention values of 15 canyon cases reflecting the dispersion ability of air pollutants from the sources out to the free stream. The results obtained indicated that the air pollutant retention value is the minimum that is favourable in a street canyon configuration for pollutant dispersion.