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Large-eddy simulation for flow and dispersion in urban streets

By Zheng-Tong Xie and Ian P. Castro


Large-eddy simulations (LES) with our recently developed inflow approach (Xie &amp;<br/>Castro, 2008a) have been used for flow and dispersion within a genuine city area -<br/>the DAPPLE site, located at the intersection of Marylebone Rd and Gloucester Pl<br/>in Central London. Numerical results up to second-order statistics are reported for<br/>a computational domain of 1.2km (streamwise) x 0.8km (lateral) x 0.2km (in full<br/>scale), with a resolution down to approximately one meter in space and one second<br/>in time. They are in reasonable agreement with the experimental data. Such a comprehensive<br/>urban geometry is often, as here, composed of staggered, aligned, square<br/>arrays of blocks with non-uniform height and non-uniform base, street canyons and<br/>intersections. Both the integrative and local effect of flow and dispersion to these<br/>geometrical patterns were investigated. For example, it was found that the peaks<br/>of spatially averaged urms, vrms, wrms and &lt; u0w0 &gt; occurred neither at the mean<br/>height nor at the maximum height, but at the height of large and tall buildings. It<br/>was also found that the mean and fluctuating concentrations in the near-source field<br/>is highly dependent on the source location and the local geometry pattern, whereas<br/>in the far field (e.g. &gt;0.1km) they are not. In summary, it is demonstrated that<br/>full-scale resolution of around one meter is sufficient to yield accurate prediction of<br/>the flow and mean dispersion characteristics and to provide reasonable estimation<br/>of concentration fluctuation

Topics: GE, QC, TA
Year: 2009
OAI identifier:
Provided by: e-Prints Soton

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