11.5
Large-eddy simulation of pollutant transport in the urban canopy layer over 2D idealized street canyons
Colman C.C. Wong, The University of Hong Kong, Hong Kong, Hong Kong SAR, Hong Kong; and C. H. Liu
Computational fluid dynamics (CFD) is an effective means for the modelling of flow and air pollutant transport in the atmospheric boundary layer (ABL). There are numerous studies concerning the flow structure and pollutant transport above smooth surface as well as arrays of buildings. The studies focusing on the flow over two-dimensional (2D) street canyons are rather limited, which, however could affect the pollutant transport substantially. In this study, large‐eddy simulation (LES) with the one-equation subgrid‐scale (SGS) model is adopted to investigate the flow structure and the pollutant transport in the urban canopy layer (UCL) over idealized 2D street canyon. The two point autocorrelation of streamwise velocity Ruu(δx) in the streamwise direction attains a value of 0.1 at a separation δx which is less than half the domain size, suggesting that the current LES domain size is merely large enough covering the most significant energy-carrying scales. The preliminary results show that even with the re-circulating flow within the street canyons, the pollutant distribution above the roof level follows fairly close the Gaussian shape. Only the roof-level pollutant profiles exhibit mild dissimilarities compared with the Gaussian plume. The Gaussian Plume model therefore should be applied with caution in these regions.
Session 11, Urban Canopy and Roughness Sublayers II
Thursday, 5 August 2010, 3:30 PM-5:00 PM, Crestone Peak I & II
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