Weijun Li1, Yuanping He1,2, Yunwei Zhang1, Qingxiang Shui1, Xinyi Wu1, Chuck Wah. Yu1,3, Zhaolin Gu 1

Department of Earth and Environmental Sciences, Xi’an Jiaotong University, Xi’an, 710049, China
Department of Architecture and Civil Engineering, City University of Hong Kong, Kowloon Tong, HKSAR, Hong Kong
International Society of the Built Environment (ISBE), Milton Keynes, MK7 8HQ, UK



Download Citation: ||https://doi.org/10.4209/aaqr.2019.06.0322 

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Cite this article:

Li, W., He, Y., Zhang, Y., Shui, Q., Wu, X., Yu, C.W. and Gu, Z. (2020). Numerical Study of the Composite Effects of Uneven Street Canyons and Time-varying Inflows on the Air Flows and Pollutant Dispersion. Aerosol Air Qual. Res., https://doi.org/10.4209/aaqr.2019.06.0322


HIGHLIGHTS

  • Acquiring appropriate time-varying condition from measured wind velocity data.
  • A new scheme solving the time-series flow fields under time-varying inflows.
  • Uneven building layouts improving the removal efficiency of pollutants.
  • Time-varying inflow improving the removal efficiency of pollutants.
  • The composite effects are not the simply additive of the two factors.
 

ABSTRACT


The dispersion behavior of pollutants in realistic street canyons is dominated by the pattern of airflow, which is closely linked to the building layout and air inflow at the street canyon boundary. The individual effects of either uneven building layouts or time-varying inflows on the airflow pattern and pollutant dispersion in street canyons, but not the combined effect, has been investigated previously. In this study, four street canyon models, including one even and three uneven models with different occupying ratios of high-rise buildings, were numerically studied using large-eddy simulation under the conditions of a steady inflow and time-varying inflows. Results showed that both the uneven building layouts and time-varying inflow condition enhanced the strength of airflow and pollutant removal efficiency inside the street canyon. However, the composite effects of these factors were not simply additive. The airflow in the even street canyon under the steady inflow condition, usually taken as the benchmark, was observed to have the worst pollutant removal efficiency. Under the time-varying inflow condition, the height of pollutant dispersion was not restricted by relatively tall high-rise buildings during the inflow in the valley because of the induced updrafts. The pattern of the pollutant isoconcentration plane and time-series curves of normalized pollutant concentrations in the even and uneven street canyon models exhibited fluctuant features under time-varying inflow condition.


Keywords: Airflow pattern; Large-eddy simulation; Pollutant dispersion; Time-varying inflow; Uneven building layouts.


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5-Year Impact Factor: 2.827


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