P. Mejean

Modelling the transport and dispersion of pollutants in street canyons

The transport and dispersion of pollutants in a street canyon, and the intersection between two streets, have been studied using wind-tunnel experiments and numerical simulations. The study of the street canyon demonstrates the importance of the geometry of the canyon (aspect ratio, asymmetry) in determining both the topology of the flow and the concentration distribution; the flow is also very sensitive to wind direction. The study of the street intersection shows how the intersection influences the flow and dispersion in the adjoining streets. This work has been used to develop new and practical models for flow and dispersion in city streets; these models are compared here with the results from wind-tunnel experiments and numerical simulations.

Measurements and CFD simulations of flow and dispersion in urban geometries

Dispersion in urban areas is determined by transport and mixing processes within the street network and ventilation into the external atmosphere. In order to improve the understanding of the exchange mechanisms within the urban canopy, wind tunnel and numerical investigations have been performed on two idealised typical urban configurations, the street intersection and the square. The numerical simulations were compared to the experimental values, in order to evaluate the reliability of the numerical approach in simulating local flow patterns and study the influence of the geometrical layout on mass and momentum exchange mechanisms.