Abstract
A comparison between numerical simulations and wind tunnel modelling has been performed to examine the variation with streamwise aspect ratio (width/height, W/H) of the mean flow patterns in a street canyon. For this purpose a two-dimensional (2-D) cavity was subjected to a thick turbulent boundary layer flow perpendicular to its principal axis. Five different test cases, W/H = 0.3, 0.5, 0.7, 1.0 and 2.0, have been studied experimentally with flow measurements taken using pulsed-wire anemometry. The results show that the skimming flow regime, with a large vortex in the canyon, occurred for all the cases investigated. For the cavities with W/H ≤ 0.7 a weaker secondary circulation developed beneath the main vortex. The narrower the canyon, the smaller the wind speed close to the cavity ground, giving increasingly poor ventilation qualities. The corresponding numerical results were obtained with the Computational Fluid Dynamics (CFD) code CHENSI that uses the standard k-ε model. The intercomparison showed good agreement in terms of the gross features of the mean flow for all the geometries examined, although some detailed differences were observed.
This is a preview of subscription content, log in via an institution to check access.
Similar content being viewed by others
References
Assimakopoulos, V., ApSimon, H., Sahm, P. and Moussiopoulos, N.: 2000, ‘Effects of Street Canyon Geometry on the Dispersion Characteristics in Urban Areas’, Proceedings of the 16th IMACS World Congress, 21–25 August 2000, Lausanne, Switzerland.
Berkowicz, R., Hertel, O., Larsen, S. E., Sorensen, N. N. and Nielsen, M.: 1997, Modelling Traffic Pollution in Streets, NERI, Roskilde, Denmark.
Castro, I. P. and Cheun, B. S.: 1982, ‘The measurement of Reynolds stresses with a pulsed-wire anemometer’, J. Fluid Mech. 118, 41–58.
Dabberdt, W. F. and Hoydysh, W. G.: 1991, ‘Street canyon dispersion: Sensitivity to block shape and entrainment’, Atmosph. Environ. 25A, 1143–1153.
DePaul, F. T. and Sheih, C. M.: 1986, ‘Measurements of wind velocities in a street canyon’, Atmosph. Environ. 20, 555–559.
Hanjàlic, R. and Launder, B. E.: 1972, ‘A Reynolds stress model of turbulence and its application to thin shear flows’, J. Fluid Mech. 52, 609–638.
Hirt, C. W., Nichols, B. D. and Romero, N. C.: 1975, ‘Sola: A Numerical Solution for Transient Fluid Flows’, Report LA5852, Los Alamos Laboratory, University of California, Los Alamos Scientific Laboratory, New Mexico 87544, U.S.A.
Hunt, A.: 1981, ‘Scale Effects on Wind Tunnel Measurements of Surface Pressures on Model Buildings’, ‘Designing with the Wind, CSTB, Nantes, France.
Hunter, L. J., Johnson, G. T. and Watson, I. D.: 1992, ‘An investigation of three-dimensional characteristics of flow regimes within the urban canyon’, Atmosph. Environ. 26B, 425–432.
Jensen, M.: 1958, ‘The model law phenomena in natural wind’, Ingenioren 2,4.
Johnson, G. T. and Hunter, L. J.: 1999, ‘Some insights into typical urban canyon airflows’, Atmosph. Environ. 33, 3991–3999.
Kastner-Klein, P. and Plate, E.J.: 1999, ‘Wind tunnel study of concentration fields in street canyon’, Atmosph. Environ. 33, 3973–3979.
Kovar-Panskus, A., Moulinneuf, L., Savory, E., Abdelqari, A., Sini, J.-F., Rosant, J.-M., Robins, A. and Toy, N.: 2002, ‘A wind tunnel investigation of the influence of solar-induced wall-heating on the flow regime within a simulated urban street canyon’, Water, Air, and Soil Pollut., this issue.
Launder, B. E. and Spalding, D. B.: 1974, ‘The numerical computation of turbulent flows’, Comp. Meth. Appl. Mech. Eng. 3, 269–289.
Liedtke, J., Leitl, B. and Schatzmann, M.: 1999, ‘Dispersion in a street canyon: comparison of wind tunnel experiments with field measurements’, in P. M. Borrel and P. Borrel (eds), Proc. of Eurotrac Symposium' 98, WIT Press, Southampton, pp. 806–810.
Leitl, B., Chauvet, C. and Schatzmann, M.: 2001, ‘Effects of Geometrical Simplifications and Ideal-ization on the Accuracy of Microscale Dispersion Modelling’, Extended abstract for the 3rd International Conference on Urban Air Quality, 19–23 March 2001, Loutraki, Greece.
M.I.H.U.: 2001, Internet database, available at University of Hamburg, funded by the Umweltbundes-amt: http://www.mi.uni-hamburg.de/cedval/categoryB.htm#B1–5.
Nakamura, Y. and Oke, T. R.: 1988, ‘Wind, temperature and stability conditions in an E–W-oriented canyon’, Atmosph. Environ. 22, 2691–2700.
Oke, T. R.: 1987, Boundary Layer Climates, 2nd ed., Routledge, New York.
Pavageau, M., Rafailidis, S. and Schatzmann, M.: 1996, ‘A Comprehensive Experimental Databank for the Verification of Urban Car Emission Dispersion Models’, Proceedings of the 4th Workshop on Harmonisation within Atmospheric Dispersion Modelling for Regulatory Purposes, 6–9 May 1996, Ostende.
Rafailidis, S.: 1997, ‘Influence of building area density and roof shape on the wind characteristics above a town’, Bound. Layer Meteor. 85, 255–271.
Sahm, P., Louka, P., Ketzel, M., Guilloteau E. and Sini, J. F.: 2002, ‘Intercomparison of numerical urban dispersion models-Part I: Street canyon and single building configurations’, Water, Air and Soil Pollut., this issue.
Scaperdas, A.: 2000, ‘Modelling Air Flow and Pollutant Dispersion at Urban Canyon Intersections’, Ph.D. Thesis, University of London.
Sini, J.-F., Anquetin, S. and Mestayer, P.: 1996, ‘Pollutant dispersion and thermal effects in urban street canyons’, Atmosph. Environ. 30, 2659–2677.
Theurer, W.: 1994, ‘Ausbreitung bodennaher Emissionen in komplexen Bebauungen’, Mitteilungen, Heft 45, Institut für Hydrologie und Wasserwirtschaft, Universität Karlsruhe, Germany.
Author information
Authors and Affiliations
Corresponding author
Rights and permissions
About this article
Cite this article
Kovar-Panskus, A., Louka, P., Sini, JF. et al. Influence of Geometry on the Mean Flow within Urban Street Canyons – A Comparison of Wind Tunnel Experiments and Numerical Simulations. Water, Air, & Soil Pollution: Focus 2, 365–380 (2002). https://doi.org/10.1023/A:1021308022939
Issue Date:
DOI: https://doi.org/10.1023/A:1021308022939