The impact of urban street layout on local atmospheric environment

The investigation was carried out to reveal the impact of urban street layout on local atmospheric environment through computational fluid dynamics (CFD) numerical simulations using standard k$k$–ε$\epsilon$ turbulence model. Different street canyon configurations are considered and the flow regimes summarized according to the aspect ratio of the leeward building height and the street width H1/W$H1/W$ and the aspect ratio of the leeward building height and the windward building height H1/H2$H1/H2$. Three regimes are defined to denote the vortices and characteristics of pollutant dispersion in street canyons according to the parameters H1/W$H1/W$ and H1/H2$H1/H2$. It is found that the pollutant transport and diffusion is strongly dependent upon the type of flow regime inside the canyon and exchange between canyon and the above roof air. The study indicated that there is a strong influence of the street layout on the wind field and the pollutant dispersion in the street canyon mainly depends on the vortex structure in the canyon. The results are validated against an extensive wind tunnel experimental (Meroney and Rafailidis) Journal of Wind Engineering and Industrial Aerodynamics, 1996;62:37–56; http://www.mi.uni-hamburg.de] and the simulated results concluded by Sini Atmospheric Environment 1996;30:2659–77] and Sang Atmospheric Environment 2002;36:1137–45].