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Turbulent Structure of a Simplified Urban Fluid Flow Studied Through Stereoscopic Particle Image Velocimetry
2018 (English)In: Boundary-layer Meteorology, ISSN 0006-8314, E-ISSN 1573-1472, Vol. 166, no 2, p. 239-268Article in journal (Refereed) Published
Abstract [en]

Stereoscopic particle image velocimetry was used to provide a three-dimensional characterization of the flow around a simplified urban model defined by a 5 by 7 array of blocks, forming four parallel streets, perpendicular to the incoming wind direction corresponding to a zero angle of incidence. Channeling of the flow through the array under consideration was observed, and its effect increased as the incoming wind direction, or angle of incidence (AOI), was changed from to , , and . The flow between blocks can be divided into two regions: a region of low turbulence kinetic energy (TKE) levels close to the leeward side of the upstream block, and a high TKE area close to the downstream block. The centre of the arch vortex is located in the low TKE area, and two regions of large streamwise velocity fluctuation bound the vortex in the spanwise direction. Moreover, a region of large spanwise velocity fluctuation on the downstream block is found between the vortex legs. Our results indicate that the reorientation of the arch vortex at increasing AOI is produced by the displacement of the different TKE regions and their interaction with the shear layers on the sides and top of the upstream and downstream blocks, respectively. There is also a close connection between the turbulent structure between the blocks and the wind gusts. The correlations among gust components were also studied, and it was found that in the near-wall region of the street the correlations between the streamwise and spanwise gusts were dominant for all four AOI cases. At higher wall-normal positions in the array, the correlation decreased with increasing AOI, whereas the coefficient increased as AOI increased, and at all three correlations exhibited relatively high values of around 0.4.

Place, publisher, year, edition, pages
SPRINGER , 2018. Vol. 166, no 2, p. 239-268
Keywords [en]
Arch vortex, Atmospheric boundary layer, Coherent structures, Stereoscopic particle image velocimetry, Urban-type flow
National Category
Fluid Mechanics and Acoustics
Identifiers
URN: urn:nbn:se:kth:diva-222172DOI: 10.1007/s10546-017-0303-9ISI: 000422982900004Scopus ID: 2-s2.0-85032657127OAI: oai:DiVA.org:kth-222172DiVA, id: diva2:1180901
Note

QC 20180207

Available from: 2018-02-07 Created: 2018-02-07 Last updated: 2018-02-07Bibliographically approved

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  • apa
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