Linking of pedestrian spaces to optimize outdoor air ventilation and quality in tropical high-density urban areas

Pedestrian spaces in cities allow a large number of outdoor activities. However, they are vulnerable to vehicular pollutants. This study aims to investigate how pedestrian spaces should be linked to optimize wind conditions and air quality in tropical cities. Numerical simulations are conducted to evaluate various upwind-to-downwind linking patterns in urban areas with three levels of high-density. The results suggest that wind velocity and pollutant concentration can be effectively optimized by adjusting their linking patterns even without compromising building density. However, wind velocity and pollutant concentration are not always inversely related. Key findings are achieved: 1) expanding pedestrian spaces particularly those at the upwind of a vehicle road introduces more prevailing wind which improves both air ventilation and quality in most scenarios; 2) offsetting pedestrian spaces at the upwind/downwind of a vehicle road generates more displacement (i.e., span-wise and vertical) flow which enhances pollutant dispersion; 3) diverging pedestrian spaces from the upwind to downwind restricts transmitting pollutants to the downwind; and 4) diversifying urban block configurations with more non-uniform linking patterns improves air quality but is less useful to wind conditions. A better-ventilated pedestrian environment is expected to encourage outdoor activities, promoting sustainable living styles and vibrant mixed-use urban developments.