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Near-surface flows over random (urban) roughness

Near-surface flows over random (urban) roughness
Near-surface flows over random (urban) roughness
Comprehensive sets of vertical mean velocity and turbulence quantities have been obtained at 64 spatial locations within a unit (plan) area of random roughness. The roughness consisted of rectangular blocks arranged in a regular staggered pattern covering 25% of the wall surface. Each element had the same square cross-section in the horizontal but the heights were randomised. The dispersive stress arising in the roughness sublayer from the spatial inhomogeneity in the mean flow profiles was calculated and is shown to be negligible compared with the usual Reynolds stresses. The data are also compared with corresponding data for a uniform-height roughness of the same pattern and total volume. It is shown that the inertial sublayer, although having an upper limit which is almost identical to that of the uniform surface, is much thinner (i.e. the roughness sublayer was much thicker for the random surface than for the uniform surface). We conclude that the inertial sublayer may not exist at all in some urban areas in which the dominant features are high, irregular and heterogeneous roughness elements.
Cheng, H.
de8f13f3-1d85-48b6-a9da-54fa69571688
Castro, I.P.
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Cheng, H.
de8f13f3-1d85-48b6-a9da-54fa69571688
Castro, I.P.
66e6330d-d93a-439a-a69b-e061e660de61

Cheng, H. and Castro, I.P. (2000) Near-surface flows over random (urban) roughness. UWERN Annual Conference 2000. 18 - 20 Dec 2000.

Record type: Conference or Workshop Item (Other)

Abstract

Comprehensive sets of vertical mean velocity and turbulence quantities have been obtained at 64 spatial locations within a unit (plan) area of random roughness. The roughness consisted of rectangular blocks arranged in a regular staggered pattern covering 25% of the wall surface. Each element had the same square cross-section in the horizontal but the heights were randomised. The dispersive stress arising in the roughness sublayer from the spatial inhomogeneity in the mean flow profiles was calculated and is shown to be negligible compared with the usual Reynolds stresses. The data are also compared with corresponding data for a uniform-height roughness of the same pattern and total volume. It is shown that the inertial sublayer, although having an upper limit which is almost identical to that of the uniform surface, is much thinner (i.e. the roughness sublayer was much thicker for the random surface than for the uniform surface). We conclude that the inertial sublayer may not exist at all in some urban areas in which the dominant features are high, irregular and heterogeneous roughness elements.

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More information

Published date: 2000
Venue - Dates: UWERN Annual Conference 2000, 2000-12-18 - 2000-12-20

Identifiers

Local EPrints ID: 21349
URI: http://eprints.soton.ac.uk/id/eprint/21349
PURE UUID: 47cab792-1f65-452a-86d7-410c6775f8bc

Catalogue record

Date deposited: 19 Feb 2007
Last modified: 17 Jul 2017 16:26

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Contributors

Author: H. Cheng
Author: I.P. Castro

University divisions

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