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


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.


Buoyancy dominant flow Buoyancy parameter CFD simulations  Urban street canyons 



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.


  1. 1.
    Allegrini J, Dorer V, Carmeliet J (2013) Wind tunnel measurements of buoyant flows in street canyons. Build Environ 59:315–326CrossRefGoogle Scholar
  2. 2.
    ANSYS Inc. (2012) ANSYS Fluent 14.0 Theory GuideGoogle Scholar
  3. 3.
    Britter RE, Hanna SR (2003) Flow and dispersion in urban areas. Ann Rev Fluid Mech 35(1):469–496CrossRefGoogle Scholar
  4. 4.
    Cai X (2012) Effects of wall heating on flow characteristics in a street canyon. Bound-Lay Meteorol 142(3):443–467CrossRefGoogle Scholar
  5. 5.
    Cai X (2012) Effects of differential wall heating in street canyons on dispersion and ventilation characteristics of a passive scalar. Atmos Environ 51:268–277CrossRefGoogle Scholar
  6. 6.
    Castro IP, Robins AG (1977) The flow around a surface-mounted cube in uniform and turbulent streams. J Fluid Mech 79(02):307–335CrossRefGoogle Scholar
  7. 7.
    Dallman A, Magnusson S, Britter RE, Norford L, Entekhabi D, Fernando HJS (2014) Conditions for thermal circulation in urban street canyons. Build EnvironGoogle Scholar
  8. 8.
    Department of Economic and Social Affairs (UN DESA). (2012) World Urbanization Prospects 2011 highlights. Technology. Accessed 30 Apr 2012
  9. 9.
    Fernando HJS, Zajic D, Di Sabatino S, Dimitrova R, Hedquist B, Dallman A (2010) Flow, turbulence, and pollutant dispersion in urban atmospheres. Phys Fluids 22(5):051301CrossRefGoogle Scholar
  10. 10.
    Kim JJ, Baik JJ (1999) A numerical study of thermal effects on flow and pollutant dispersion in urban street canyons. J Appl Meteorol 38(9):1249–1261CrossRefGoogle Scholar
  11. 11.
    Kim JJ, Baik JJ (2004) A numerical study of the effects of ambient wind direction on flow and dispersion in urban street canyons using the RNG k-\(\varepsilon \) turbulence model. Atmos Environ 38(19):3039–3048CrossRefGoogle Scholar
  12. 12.
    Li XX, Britter RE, Koh TY, Norford L, Liu CH, Entekhabi D, Leung DYC (2010) Large-Eddy simulation of flow and pollutant transport in urban street canyons with ground heating. Bound-Lay Meteorol 137(2):187–204CrossRefGoogle Scholar
  13. 13.
    Li XX, Britter RE, Norford L, Koh TY, Entekhabi D (2012) Flow and pollutant transport in urban street canyons of different aspect ratios with ground heating: Large-Eddy simulation. Bound-Lay Meteorol 142:289–304CrossRefGoogle Scholar
  14. 14.
    Look P, Belcher S, Harrison R (2000) Coupling between air flow in streets and the well-developed boundary layer aloft. Atmos Environ 34(16):2613–2621CrossRefGoogle Scholar
  15. 15.
    Louka P, Vachon G, Sini JF, Mestayer PG, Rosant JM (2002) Thermal effects on the airflow in a street canyon—Nantes’99 experimental results and model simulations. Water Air Soil Pollut 2(5–6):351–364CrossRefGoogle Scholar
  16. 16.
    Oke TR (1988) Street design and urban canopy layer climate. Energy Build 11(1):103CrossRefGoogle Scholar
  17. 17.
    Park SB, Baik JJ, Raasch S, Letzel MO (2012) A Large-Eddy simulation study of thermal effects on turbulent flow and dispersion in and above a street canyon. J Appl Meteorol Climatol 51(5):829–841CrossRefGoogle Scholar
  18. 18.
    Richards PJ, Hoxey RP (1993) Appropriate boundary conditions for computational wind engineering models using the \(k-\epsilon \) turbulence model. J Wind Eng Ind Aerodyn 46–47:145–153CrossRefGoogle Scholar
  19. 19.
    Sini JF, Anquetin S, Mestayer PG (1996) Pollutant dispersion and thermal effects in urban street canyons. Atmos Environ 30(15):2659–2677CrossRefGoogle Scholar
  20. 20.
    Solazzo E, Britter RE (2007) Transfer processes in a simulated urban street canyon. Bound-Lay Meteorol 124(1):43CrossRefGoogle Scholar
  21. 21.
    Stull RB (1988) An Introduction to boundary layer meteorology. Springer, Berlin and New YorkCrossRefGoogle Scholar
  22. 22.
    Turner JS (1979) Buoyancy effects in fluids. Cambridge University Press, CambridgeGoogle Scholar

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

Personalised recommendations