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Environmental Fluid Mechanics

, Volume 14, Issue 6, pp 1427–1441 | Cite as

On thermally forced flows in urban street canyons

  • S. Magnusson
  • A. Dallman
  • D. Entekhabi
  • R. Britter
  • H. J. S. Fernando
  • L. Norford
Original Article

Abstract

During sunny days with periods of low synoptic wind, buoyancy forces can play a critical role on the air flow, and thus on the dispersion of pollutants in the built urban environments. Earlier studies provide evidence that when a surface inside an urban street canyon is at a higher temperature than that of local ambient air, buoyancy forces can modify the mechanically-induced circulation within the canyons (i.e., gaps between buildings). The aspect ratio of the urban canyon is a critical factor in the manifestation of the buoyancy parameter. In this paper, computational fluid dynamics simulations are performed on urban street canyons with six different aspect ratios, focusing on the special case where the leeward wall is at a greater temperature than local ambient air. A non-dimensional measure of the influence of buoyancy is used to predict demarcations between the flow regimes. Simulations are performed under a range of buoyancy conditions, including beyond those of previous studies. Observations from a field experiment and a wind tunnel experiment are used to validate the results.

Keywords

Buoyancy dominant flow Buoyancy parameter CFD simulations  Urban street canyons 

Notes

Acknowledgments

This research was supported by the Singapore National Research Foundation through the Singapore-MIT Alliance for Research and Technology’s Center for Environmental Sensing and Modeling (CENSAM). During the preparation of this paper, H.J.S. Fernando was supported by National Science Foundation (CMG; Grant # 0934592). The authors would like to thank the two reviewers for their useful comments and suggestions.

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Copyright information

© Springer Science+Business Media Dordrecht 2014

Authors and Affiliations

  • S. Magnusson
    • 1
    • 2
  • A. Dallman
    • 3
  • D. Entekhabi
    • 1
    • 2
  • R. Britter
    • 2
    • 4
  • H. J. S. Fernando
    • 3
  • L. Norford
    • 2
    • 4
  1. 1.Department of Civil- and Environmental Engineering, Parsons LaboratoryMassachusetts Institute of TechnologyCambridgeUSA
  2. 2.Center for Environmental Sensing and ModelingSingapore-MIT Alliance for Research and TechnologySingapore Singapore
  3. 3.Department of Civil- and Environmental Engineering and Earth SciencesUniversity of Notre DameNotre DameUSA
  4. 4.Department of Architecture, Building Technology ProgramMassachusetts Institute of TechnologyCambridgeUSA

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