Impacts of cross-ventilation on the air quality in street canyons with different building arrangements

The effect of cross-ventilation in buildings on air quality within street canyons is evaluated by employing computational fluid dynamic (CFD) models. The impacts of the airflow entering the canyons through the upstream building windows on flow field and pollutant distribution were investigated in both regular and staggered canyons, and the influences of window-opening-percentage (WOP) for different street width to building height aspect ratios (AR) was studied. The numerical results show that the airflow through the windows of the upstream building can destroy the primary vortex and leads to a new flow pattern within the canyon. When the WOP is increased from 0 to 10%, the ability of the flow for pollutant dilution and dispersion can be improved. This causes the' pollutant concentrations decreased by 23% to 27% in the street. And these reductions are greater for staggered arrangements than that for regular arrangements. The influences of the WOP on air flow inside the canyon decrease with increasing the AR. A limiting aspect ratio exists, beyond which the flow structure and the pollutant concentration in the canyon will not be changed no matter what the WOP is. (C) 2016 Elsevier Ltd. All rights reserved.