Impact of Sky Terrace Locations on Pedestrian Ventilation and Air Quality in High-Density Areas Using CFD Simulation

Urban ventilation significantly alleviates heat accumulation, removes air pollution, and provides outdoor thermal comfort for pedestrians in cities. Due to urbanization, a high density of building clusters can block wind flows and decrease wind velocity in the city's inner areas, which leads to uncomfortable conditions and poor air quality. Several urban morphology designs, including increasing open space and reducing the building height and degree of enclosure, could promote natural ventilation for pedestrians in urban areas. However, with the high demand for land and property prices in high-density and compact cities, such design features might not be suitable. Building permeability via sky terraces has been implemented in Hong Kong and Singapore to promote urban ventilation in high-density areas. However, there is little research on how the sky terrace locations and their application in multiple buildings could affect pedestrian wind comfort and air quality. This study investigated the effect of sky terraces of three different heights on improving air ventilation and air pollution dispersion in the central business area of Bangkok, Thailand. The wind environment and age of air were investigated using computational fluid dynamics (CFD) simulation. The results showed that the sky terraces significantly improved the air quality at the pedestrian level, and more areas had higher wind speeds and achieved wind comfort conditions. Lower-level sky terraces impacted the pedestrian wind environment more than upper-level ones. Accelerated wind passage through the bottom-level sky terraces could change local wind patterns, reducing pedestrian wind speed and comfort in some areas. The current study introduces the potential benefits and limited applications of sky terraces in a cluster of high-rise buildings to improve urban ventilation performance in a high-density area.