Abstract
A three-dimensional geometrical model was established based on a section of street canyons in the 2nd Ring Road of Wuhan, China, and a mathematical model describing the fluid flow and pollutant dispersion characteristics in the street canyon was developed. The effect of traffic tidal flow was investigated based on the measurement results of the passing vehicles as the pollution source of the CFD method and on the spatial distribution of pollutants under various ambient crosswinds. Numerical investigation results indicated that: (i) in this three-dimensional asymmetrical shallow street canyon, if the pollution source followed a non-uniform distribution due to the traffic tidal flow and the wind flow was perpendicular to the street, a leeward side source intensity stronger than the windward side intensity would cause an expansion of the pollution space even if the total source in the street is equal. When the ambient wind speed is 3 m/s, the pollutant source intensity near the leeward side that is stronger than that near the windward side (R = 2, R = 3, and R = 5) leads to an increased average concentration of CO at pedestrian breathing height by 26%, 37%, and 41%, respectively. (R is the ratio parameter of the left side pollution source and the right side pollution source); (ii) However, this feature will become less significant with increasing wind speeds and changes of wind direction; (iii) the pollution source intensity exerted a decisive influence on the pollutant level in the street canyon. With the decrease of the pollution source intensity, the pollutant concentration decreased proportionally.
Highlights
The recent urbanization process continues to advance all over the world
A three-dimensional geometrical model was established based on a section of the street canyon the 2nd Ring Road geometrical of Wuhan, China, as an apparent trafficbased tidal phenomenon occurscanyon in
The source intensity of the pollutants is typically expressed in kg/(m3 s), which is generally affected by the type of vehicles in the street, the emission rate of these vehicles, and the traffic flow
Summary
The recent urbanization process continues to advance all over the world. The rapid growth of vehicle ownership leads to motor vehicle exhaust emissions being one of the main sources of air pollution in cities [1]. Due to these health-related issues, extensive research on identifying and understanding the physical processes that both drive and influence the near-field pollutant dispersion in urban environments has experienced a substantial progress over the last three decades Most of these studies began with the basic unit of any city—the Street Canyon. The research results in this field are substantial and mature, Lateb et al [26] clearly concluded that “the topic of micro-scale dispersion still requires further investigation to understand the effect of all parameters on wind flow and pollutant dispersion in urban areas” At present, both in large and medium-sized cities, by the influence of urban planning layout and the increasing price of central area land, a new pattern of work unit has formed that focuses on the city center area, while the residential areas are mainly concentrated in peripheral regions.
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
