Building Simulation

, Volume 12, Issue 2, pp 285–297 | Cite as

Impact of indoor-outdoor temperature differences on dispersion of gaseous pollutant and particles in idealized street canyons with and without viaduct settings

  • Jian Hang
  • Riccardo BuccolieriEmail author
  • Xia Yang
  • Hongyu Yang
  • Francesca Quarta
  • Baomin WangEmail author
Research Article Indoor/Outdoor Airflow and Air Quality


Computational fluid dynamics simulations were performed to investigate flow and pollutant dispersion in a 2D street canyon of aspect ratio H/W = 1. Different from other works, the combination of the presence of viaduct and indoor-outdoor temperature differences ΔT is investigated for different approaching wind velocities. For larger wind velocity (2 m/s, Froude number Fr~3.06–12.24) the typical clockwise vortex leads to higher concentrations of both gas and small particles at the leeward side of the street and in the leeward-side rooms; the vortex is enhanced under large ΔT (20 K) improving the dispersion of pollutants. For smaller velocity (0.5 m/s, Fr~0.19–0.77) the appearance of an anti-clockwise vortex leads to a strong accumulation of gas and particles at the windward side and in the windward-side rooms under low ΔT (5 K); increasing the ΔT raises the dispersion of pollutants with consequent lower concentrations in the rooms (up to an average of 67% with respect to the isothermal case for gaseous pollutants), but accumulation close to the ground level at both windward-side and leeward-side rooms. In the presence of viaduct, together with the main vortex above the viaduct which causes concentrations increasing from low-level to high-level leeward-side rooms, two vortices are generated below it. Still ΔT = 20 K improves the dispersion of pollutants, leading up to a maximum of about 30% lower gaseous concentrations in the rooms. In general, lower concentrations of gas and particles are found for larger velocity, indicating that the mechanical turbulence dominates over the buoyancy effects, which become crucial for smaller velocity. This study confirms previous findings that viaducts may improve pollutant dispersion under large velocity if only one viaduct-level pollutant source exists and indoor-outdoor ΔT conditions can mitigate street air pollution.


computational fluid dynamics (CFD) 2D street canyon indoor-outdoor temperature difference viaduct particle number 


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This research was supported by the National Key R&D Program of China (2016YFC0202206 and 2016YFC0202205); the National Natural Science Foundation of China (No. 51478486) and National Natural Science Foundation—Outstanding Youth Foundation (No. 41622502 ) as well as Science and Technology Program of Guangzhou, China (No. 201607010066 and No. 2014B020216003).


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Copyright information

© Tsinghua University Press and Springer-Verlag GmbH Germany, part of Springer Nature 2018

Authors and Affiliations

  1. 1.School of Atmospheric SciencesSun Yat-sen UniversityGuangzhouChina
  2. 2.Guangdong Province Key Laboratory for Climate Change and Natural Disaster StudiesSun Yat-sen UniversityGuangzhouChina
  3. 3.Dipartimento di Scienze e Tecnologie Biologiche ed AmbientaliUniversity of SalentoLecceItaly

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