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Wind and Structures
  Volume 8, Number 6, November 2005 , pages 427-442

Numerical and wind tunnel simulation of pollutantrndispersion in the near wake of buildings
X. Wang and K.F. McNamara

    Numerical and wind tunnel simulations of pollutant dispersion around rectangular obstacles with five aspect ratios have been conducted in order to identify the effects of flow patterns induced by buildings on plume dispersion in the near wake of buildings. An emission from a low source located upwind of obstacles was used in this simulation. The local flow patterns and concentrations around a cubical obstacle were initially investigated using three RANS turbulence models, (the standard k-e, Shear Stress Transport (SST), Reynolds-Stress RSM turbulence model) and also using Large-eddy simulation (LES). The computed concentrations were compared with those measured in the wind tunnel. Among the three turbulence models, the SST model offered the best performance and thus was used in further investigations. The results show, for normal aspect ratios of width to height, that concentrations in the near wake are appreciably affected because of plume capture by the horseshoe vortex and convection by the vertical vortex pairs. These effects are less important for high aspect ratios. Vertical vortex pairs present a strong ability to exchange mass vertically and acts efficiently to reduce ground-level concentrations in the near wake.
Key Words
    dispersion; building effects; horseshoe vortex; vertical vortex pairs; near wake.
Department of Civil Engineering, National University of Ireland, Galway, Ireland

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