The University of Southampton
University of Southampton Institutional Repository

Unsteady dynamics and organized structures from DNS over an idealized building canopy (In special issue: Urban Climatology ICUC6)

Unsteady dynamics and organized structures from DNS over an idealized building canopy (In special issue: Urban Climatology ICUC6)
Unsteady dynamics and organized structures from DNS over an idealized building canopy (In special issue: Urban Climatology ICUC6)
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.
dns, coherent structures, turbulent organized structures, urban canopy
1943-1953
Coceal, Omduth
c89d9de1-c311-4203-b6ea-b72eb48fa4f9
Dobre, Adrian
0217d643-b8e7-413b-acfb-6d2b92dc93b4
Thomas, T.G.
bccfa8da-6c8b-4eec-b593-00587d3ce3cc
Coceal, Omduth
c89d9de1-c311-4203-b6ea-b72eb48fa4f9
Dobre, Adrian
0217d643-b8e7-413b-acfb-6d2b92dc93b4
Thomas, T.G.
bccfa8da-6c8b-4eec-b593-00587d3ce3cc

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).

Record type: Article

Abstract

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.

Text
unsteady_dynamics_and_organized_structures_from_DNS_over_an_idealized_building_canopy.pdf - Version of Record
Download (1MB)

More information

Published date: 5 July 2007
Keywords: dns, coherent structures, turbulent organized structures, urban canopy
Organisations: Aerodynamics & Flight Mechanics

Identifiers

Local EPrints ID: 48207
URI: http://eprints.soton.ac.uk/id/eprint/48207
PURE UUID: 5dc8797e-17bf-44a6-9751-f4156c6ec956

Catalogue record

Date deposited: 19 Dec 2008
Last modified: 16 Dec 2019 19:18

Export record

Altmetrics

Contributors

Author: Omduth Coceal
Author: Adrian Dobre
Author: T.G. Thomas

University divisions

Download statistics

Downloads from ePrints over the past year. Other digital versions may also be available to download e.g. from the publisher's website.

View more statistics

Atom RSS 1.0 RSS 2.0

Contact ePrints Soton: eprints@soton.ac.uk

ePrints Soton supports OAI 2.0 with a base URL of http://eprints.soton.ac.uk/cgi/oai2

This repository has been built using EPrints software, developed at the University of Southampton, but available to everyone to use.

We use cookies to ensure that we give you the best experience on our website. If you continue without changing your settings, we will assume that you are happy to receive cookies on the University of Southampton website.

×