Computational Fluid Dynamics Simulation of the Influence of Street Interface Density on Natural Ventilation and Pollutants Diffusion in Urban Streets

Objectives Prior to the advent of low-carbon travel, the air pollution arising from vehicle exhaust emissions within the urban canopy layer has remained a significant challenge in the governance of urban atmospheric environments.

Methods This paper presents a series of three-dimensional physical models representing typical urban streets, with varying street interface density (SID). The models employ the computational fluid dynamics (CFD) simulations to assess the impact of SID on airflow patterns and pollutant dispersion. Metrics such as air exchange rate, purging flow rate, average residence time, and pollutant concentration in pedestrian areas are utilized to evaluate the natural ventilation performance and pollutant diffusion capacity across urban streets with different SIDs.

Results The findings illustrate that the CFD simulation approach is an effective means of elucidating the intricate details of airflow and pollutant dispersion within urban street spaces. A reduction in SID on both sides of urban streets has been demonstrated to enhance natural ventilation and air quality. Notably, a decrease in the upstream SID has a more pronounced effect on improving air quality compared to that of the downstream. The arrangement of buildings adjacent to urban streets significantly impacts the overall ventilation performance and pollutant dispersion capacity under different SIDs, with a critical upstream SID value of approximately 0.8.

Conclusions The proposed CFD simulation method can facilitate a comprehensive understanding of airflow and pollutant dispersal mechanisms, thereby enabling more scientific planning and design control of urban street spaces. Furthermore, it helps to provide proactive strategies for residents residing near urban streets to cope with traffic-related air pollution risks.