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Article

Ventilation and Pollutant Concentration for the Pedestrian Zone, the Near-Wall Zone, and the Canopy Layer at Urban Intersections

by 1, 2,1,*, 1 and 3
1
School of Architecture and Urban Planning, Nanjing University, 22 Hankou Road, Nanjing 210093, China
2
Joint International Research Laboratory of Eco-Urban Design, Tongji University, Ministry of Education, 1239 Siping Road, Shanghai 200092, China
3
Department of Mechanical and Aerospace Engineering, Syracuse University, Syracuse, NY 13210, USA
*
Author to whom correspondence should be addressed.
Academic Editor: Chunrong Jia
Int. J. Environ. Res. Public Health 2021, 18(21), 11080; https://doi.org/10.3390/ijerph182111080
Received: 14 August 2021 / Revised: 7 October 2021 / Accepted: 19 October 2021 / Published: 21 October 2021
To gain further insight into the ventilation at urban street intersections, this study conducted 3D simulations of the ventilation at right- and oblique-angled intersections under eight wind directions by using the Reynolds-averaged Navier–Stokes (RANS) κ-ε turbulence model. The divergent responses of ventilation and pollution concentration for the pedestrian zone (ped), the near-wall zone (nwz), and the canopy layer to the change in intersection typology and wind direction were investigated. The flow characteristics of the intersections, taken as the air flow hub, were explored by employing indices such as the minimum flow ratio (β) between horizontal openings. The results show that oblique wind directions lead to a lower total volumetric flow rate (Qtotal) but a higher β value for right-angled intersections. For T-shaped intersections, a larger cross-sectional area for the outflow helps to increase Qtotal. Oblique-angled intersections, for example, the X-shaped intersection, experience a more significant difference in Qtotal but a steady value of β when the wind direction changes. The vertical air-exchange rate for the intersection was particularly significant when the wind directions were parallel to the street orientation or when there was no opening in the inflow direction. The spatially averaged normalized pollutant concentration and age of air (τ*¯) for the pedestrian zone and the canopy layer showed similar changing trends for most of the cases, while in some cases, only the τped*¯ or τnwz*¯ changed obviously. These findings reveal the impact mechanism of intersection configuration on urban local ventilation and pollutant diffusion. View Full-Text
Keywords: intersections typology; CFD simulations; pedestrian ventilation; near-wall concentration; volumetric flow rate; age of air intersections typology; CFD simulations; pedestrian ventilation; near-wall concentration; volumetric flow rate; age of air
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MDPI and ACS Style

Zhang, M.; Gao, Z.; Guo, X.; Shen, J. Ventilation and Pollutant Concentration for the Pedestrian Zone, the Near-Wall Zone, and the Canopy Layer at Urban Intersections. Int. J. Environ. Res. Public Health 2021, 18, 11080. https://doi.org/10.3390/ijerph182111080

AMA Style

Zhang M, Gao Z, Guo X, Shen J. Ventilation and Pollutant Concentration for the Pedestrian Zone, the Near-Wall Zone, and the Canopy Layer at Urban Intersections. International Journal of Environmental Research and Public Health. 2021; 18(21):11080. https://doi.org/10.3390/ijerph182111080

Chicago/Turabian Style

Zhang, Mingjie, Zhi Gao, Xin Guo, and Jialei Shen. 2021. "Ventilation and Pollutant Concentration for the Pedestrian Zone, the Near-Wall Zone, and the Canopy Layer at Urban Intersections" International Journal of Environmental Research and Public Health 18, no. 21: 11080. https://doi.org/10.3390/ijerph182111080

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