Environmental Fluid Mechanics

, Volume 5, Issue 5, pp 393–413 | Cite as

Upstream Turbulence Effect on Pollution Dispersion

  • Ijaz M. Khan
  • Richard R. Simons
  • Anthony J. Grass


Experiments have been carried out to investigate turbulence at and above roof-level in an urban environment, and to predict the behaviour of street pollution from experiments using dye dispersion, for different roughness conditions and bed geometries. The flow in the boundary layer above an idealised urban environment has been simulated in a laboratory water flume. Comparisons have been made for the same model street canyon with and without the presence of upstream roughness. In the tests reported here, model street canyons were aligned perpendicular to the flow direction, and velocity measurements made within and above the model street canyons using a laser Doppler velocimeter (LDV). Flow visualisation techniques have also been used to confirm the gross flow features from streak images. Turbulence generated from the upstream roughness has a significant effect on the turbulence production and dispersion behaviour of the dye simulating pollution in street canyons.


flow pattern internal boundary layer pollution dispersion sudden change in bed roughness surface roughness turbulence 



height of upstream slat of the immediate large scale roughness


height of downstream slat of the immediate large scale roughness


flow depth in the water flume


hyperbolic hole


height of upstream slat of the model street canyon


height of tall downstream slat of the model street canyon


roughness element height


gap distance between immediate large scale roughness slats


gap distance between roughness slats of immediate large scale roughness and model street canyon


gap distance between the roughness slats of model street canyon


instantaneous stream wise velocity


fluctuating stream wise velocity component


root mean square value for U


local mean stream wise velocity


bed shear velocity


instantaneous vertical velocity


fluctuating vertical velocity component

\(\sqrt{\overline{w^{\prime2}}} \)

root mean square value for W


local mean vertical velocity


vertical distance from the roof level of roughness element for various positions where LDV measurements were made


vertical distance from the wall to the roof level of the roughness element for various positions where LDV measurements were made


roughness length scale


vertical distance from the effective origin of mean velocity profile


Reynolds stress


stream wise position at roof-level between the roughness elements


origin correction shift


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Copyright information

© Springer 2006

Authors and Affiliations

  • Ijaz M. Khan
    • 1
  • Richard R. Simons
    • 2
  • Anthony J. Grass
    • 2
  1. 1.Department of Chemical EngineeringThe University of BirminghamEdgbastonUK
  2. 2.Civil and Environmental Engineering DepartmentUniversity College LondonLondonUK

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