Unsteady dynamics and organized structures from DNS over an idealized building canopy (In special issue: Urban Climatology ICUC6)
Coceal, Omduth, Dobre, Adrian and Thomas, T.G. (2007) Unsteady dynamics and organized structures from DNS over an idealized building canopy (In special issue: Urban Climatology ICUC6). International Journal of Climatology, 27, (14), 1943-1953. (doi:10.1002/joc.1549).
- Publishers print
A numerical study is performed to elucidate the dominant turbulent processes that occur in urban areas. Comprehensive data from direct numerical simulations (DNS) over idealized three-dimensional arrays of buildings are analysed to study the unsteady and organized aspects of the turbulent flow. The accuracy of the DNS is evaluated by comparing turbulence statistics with a high quality wind-tunnel dataset. The simulation results are studied using flow visualization as well as statistical methods including quadrant analysis, space-time two-point correlations and conditional averaging. Three regimes of the flow are identified. First, the rough wall flow above the buildings has turbulent organized structures that resemble the hairpin vortices and low momentum regions that are well known to occur in the turbulent boundary layer over smooth walls. These hairpin-like vortices contribute dominantly to vertical momentum transport. Secondly, shear layers develop over the tops of the buildings and shed structures that may sometimes impinge upon downstream buildings and drive a robust recirculation within the building canopy. These unsteady canopy-top shear layers and their interaction with the larger eddies above provide important mechanisms for coupling with the flow within the canopy. Thirdly, the flow within the building canopy is the result of complicated interactions between the above and eddies shed off the vertical edges of the buildings, and their distortion caused by impacting buildings. Mean flow patterns around the buildings are important and lead to significant dispersive stresses. Implications for scalar transport and dispersion are briefly discussed.
|Keywords:||dns, coherent structures, turbulent organized structures, urban canopy|
|Subjects:||Q Science > QC Physics|
|Divisions:||University Structure - Pre August 2011 > School of Engineering Sciences
University Structure - Pre August 2011 > School of Engineering Sciences > Aerodynamics & Flight Mechanics
|Date Deposited:||19 Dec 2008|
|Last Modified:||08 Jun 2012 12:18|
|Contributors:||Coceal, Omduth (Author)
Dobre, Adrian (Author)
Thomas, T.G. (Author)
|Date:||5 July 2007|
|RDF:||RDF+N-Triples, RDF+N3, RDF+XML, Browse.|
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