Impact of building façade geometrical details on pollutant dispersion in street canyons

The present study investigates the impact of building façade geometrical details on pollutant transport mechanism in long street canyons. Large-eddy simulations (LES), extensively validated with experiments, are performed for four cases: (i) canyon without balconies, (ii) balconies at both windward and leeward façades, only (iv) façade. results show that can strongly affect wind flow field dispersion most significant is observed two cases façade, which obstruct airflow from penetrating deep into bottom canyon. presence façades increase area-weighted mean concentration vertical center plane inside by 80% 106%, respectively, reduce exchange velocity (Ue) 46% 54%, respectively. analysis convective turbulent mass fluxes indicates mainly decreases contribution to Ue, while smaller.