Effects of wind direction and building array arrangement on airflow and contaminant distributions in the central space of buildings

Buildings are physical obstacles that diminish the benefits of wind by creating turbulence and reducing airflow velocities in urban settings. Particularly in the inner garden or amenities situated at the pedestrian level in the central space of a group of buildings, the efficiency of pollutant dispersion determines air quality and outdoor health. In this study, the effects of incident wind angles on wind velocity and pollutant distribution inside the central space of two building arrays arranged in ‘L’ and ‘U’ shapes were examined using computational fluid dynamics simulations. The ‘L’-shaped array performed better than the ‘U’-shaped array by forming a smaller low-wind-velocity (LWV) zone in the central space of the buildings (34.9%–76.11 % of the total space). The ‘L’-shaped array performed best at an incident wind angle of 225°, in which the LWV zone covered only 34.52 % of the central space. A 90° incident angle produced the largest LWV zone (81.80 %) for the ‘U’-shaped array. The ‘L’-shaped array generally distributed pollutants better than the ‘U’-shaped array. However, the ‘U’-shaped array with a 180° wind angle had a smaller high pollutant concentration area than the ‘L’-shaped array with a wind angle of 225° (K_c > 218.5 covering only 0.37 %). The worst vertical dispersion corresponded to a 135° wind angle for the ‘L’-shaped array, which recorded the highest K_c at the mid-level of the building. In conclusion, the appropriate selection of building array designs and their orientations allows for the most effective use of wind flow to enhance ventilation and pollutant dispersion.