Effect of balconies on air quality in deep street canyons

Özet

This study discusses the effect of balconies on the dispersion of vehicular pollutants inside a deep streetcanyon and on the mass transfer rate between the canyon and the above atmosphere. 3D computationalfluid dynamics (CFD) simulations were performed considering the presence of balconies of differentdimensions in a deep street canyon with aspect ratio H/W ¼ 3. The effect of two geometrical parametershas been investigated: the balcony depth and the horizontal distance between two balconies, the othergeometrical parameters remaining constant. CFD simulations have been carried out adopting the scaleadaptive simulation (SAS) model. Results show that the presence of balconies can determine a significantmodification in the flow field inside the street canyon with a less homogeneous dispersion of pollutantsemitted by vehicles circulating in the street and a less effective mass exchange with the above atmosphere.At the present models developed to assess pollutant concentration levels in street canyons do notconsider the presence of balconies. As consequence, an underestimation of real concentration levelscould occur. Therefore, results obtained can give a contribution in the development of more feasible airpollution models in urban areas at local scale, and useful information for design of building facades thatminimize the entrapping of vehicular pollutants at pedestrian level in street canyons.