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

Author

Listed:
  • Mingjie Zhang

    (School of Architecture and Urban Planning, Nanjing University, 22 Hankou Road, Nanjing 210093, China)

  • Zhi Gao

    (School of Architecture and Urban Planning, Nanjing University, 22 Hankou Road, Nanjing 210093, China
    Joint International Research Laboratory of Eco-Urban Design, Tongji University, Ministry of Education, 1239 Siping Road, Shanghai 200092, China)

  • Xin Guo

    (School of Architecture and Urban Planning, Nanjing University, 22 Hankou Road, Nanjing 210093, China)

  • Jialei Shen

    (Department of Mechanical and Aerospace Engineering, Syracuse University, Syracuse, NY 13210, USA)

Abstract

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 (Q total ) but a higher β value for right-angled intersections. For T-shaped intersections, a larger cross-sectional area for the outflow helps to increase Q total . Oblique-angled intersections, for example, the X-shaped intersection, experience a more significant difference in Q total 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 τ ped * ¯ or τ nwz * ¯ changed obviously. These findings reveal the impact mechanism of intersection configuration on urban local ventilation and pollutant diffusion.

Suggested Citation

  • Mingjie Zhang & Zhi Gao & Xin Guo & Jialei Shen, 2021. "Ventilation and Pollutant Concentration for the Pedestrian Zone, the Near-Wall Zone, and the Canopy Layer at Urban Intersections," IJERPH, MDPI, vol. 18(21), pages 1-23, October.
  • Handle: RePEc:gam:jijerp:v:18:y:2021:i:21:p:11080-:d:661708
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    Citations

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    Cited by:

    1. Qingman Li & Jie Liang & Qun Wang & Yuntong Chen & Hongyu Yang & Hong Ling & Zhiwen Luo & Jian Hang, 2022. "Numerical Investigations of Urban Pollutant Dispersion and Building Intake Fraction with Various 3D Building Configurations and Tree Plantings," IJERPH, MDPI, vol. 19(6), pages 1-34, March.
    2. Bin Zheng & Afang Jin & Shuzhi Zhang & Hao Peng, 2023. "Numerical Simulation of Pollutant Spread in a Double-Deck Viaduct," Sustainability, MDPI, vol. 15(21), pages 1-17, October.

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