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Flow mechanisms and flow capacity in idealized long-street city models
KTH Research School University of Gävle, Department of Indoor Environment.
(KTH Research School University of Gävle, Department of Indoor Environment.
2010 (English)In: Building and Environment, ISSN 0360-1323, E-ISSN 1873-684X, Vol. 45, no 4, 1042-1053 p.Article in journal (Refereed) Published
Abstract [en]

It is an open question whether a street network of a city has a certain flow capacity characterizing the flow that can pass through the street network. It s our hypothesis that at least the simple street network has a certain flow capacity. With the purpose of exploring this we studied numerically and experimentally the flow capacity in some idealized long-street models continuously lined with buildings and exposed to a parallel approaching wind. The height of all the models is the same (H = 69 mm). Three groups of models were studied: models with the same uniform street width (W=H) but different lengths (L = 21.7H, 43.5H, 72.5H); models with the same length (L = 43.5H) but different uniform width (W = H, 2H. 4H); and models with a change of width at half distance, L/2. In the last of the three cases, the width of the upstream half was always the same (W1 = H), but there was a wider (W2 = 1.25H, 1.5H, 2H) or narrower (W2 = 0.75H, 0.5H) downstream half. We normalized flow rates by a reference flow rate equal to the flow rate through an opening far upstream with the same area as the windward entry. The normalized flow rate through the windward entry was about 1.0 in all cases. For a sufficiently long-street models, a flow balance is established, creating a fully developed region with a constant horizontal flow (flow capacity) and zero vertical mean velocity. The street length does not affect the flow capacity but as expected the width of the street affects the flow capacity.

Place, publisher, year, edition, pages
2010. Vol. 45, no 4, 1042-1053 p.
Keyword [en]
CFD simulation, Wind tunnel, Long streets, Aspect ratio, Flow rate, Total energy density
National Category
Building Technologies
URN: urn:nbn:se:kth:diva-101039DOI: 10.1016/j.buildenv.2009.10.014ISI: 000273945300030ScopusID: 2-s2.0-71649098131OAI: diva2:547651

QC 20120828

Available from: 2012-08-28 Created: 2012-08-22 Last updated: 2012-08-28Bibliographically approved

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Sandberg, MatsClaesson, Leif
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