Influence of avenue trees on traffic pollutant dispersion in asymmetric street canyons: Numerical modeling with empirical analysis

• Published in: Transportation research. Part D, Transport and environment Transport and environment, 2018-12, Vol.65, p.784-795
• Main Authors: Sun, Daniel(Jian), Zhang, Ying
• Format: Article
• Language: English
• Subjects: Computational Fluid Dynamics (CFD) simulation; Low-carbon transportation; Street canyons; Traffic pollutant; Urban traffic
• ISSN: 1361-9209; 1879-2340
• DOI: 10.1016/j.trd.2017.10.014

•Effects of avenue trees on traffic pollutant dispersion were investigated.•Simulation model for estimation pollutant concentration was developed using FLUENT.•Different wind directions and velocities are considered with and without tree scenarios.•Avenue trees increase CO concentration and human exposure in asymmetric street canyons. The dispersion of traffic-related pollutants in urban street canyons is of importance for the health and quality of lives. To reveal the inherent principle, researchers have performed a lot of investigations; many dispersion phenomena have also been assessed during recent years. However, the presence of avenue trees in street canyons and their capacity for pollutant dispersion remains partly addressed. In this study, we investigated the effects of avenue trees in urban street canyons on traffic pollutant dispersion. The dispersion of CO concentration in asymmetric street canyons was simulated under varied situations. The computational results showed a good agreement with the experimental data, and the numerical model was validated to be adequate for investigating the pollutant dispersion in street canyons. Then, the numerical simulations were extended to explore the impacts of the effects of avenue trees on CO dispersion; the results indicated that avenue trees generally increase CO concentrations in asymmetric street canyons. When the wind direction is perpendicular to the street axis, a terraced building raises pollutant concentrations at the windward wall and reduces concentration at the leeward wall on the pedestrian levels. Findings of this study are expected to provide significant insight into urban road design and strategy making for avenue tree planting, particularly under the existing worldwide sustainable low-carbon urban development.