The University of Southampton
University of Southampton Institutional Repository
Warning ePrints Soton is experiencing an issue with some file downloads not being available. We are working hard to fix this. Please bear with us.

Outer layer turbulence intensities in smooth- and rough-wall boundary layers

Outer layer turbulence intensities in smooth- and rough-wall boundary layers
Outer layer turbulence intensities in smooth- and rough-wall boundary layers
Clear differences in turbulence intensity profiles in smooth, transitional and fully rough zero-pressure-gradient boundary layers are demonstrated, using the diagnostic plot introduced by Alfredsson, Segalini & Örlü (Phys. Fluids, vol. 23, 2011, p. 041702) – u?/U versus U/Ue, where u? and U are the local (root mean square) fluctuating and mean velocities and Ue is the free stream velocity. A wide range of published data are considered and all zero-pressure-gradient boundary layers yield outer flow u?/U values that are roughly linearly related to U/Ue, just as for smooth walls, but with a significantly higher slope which is completely independent of the roughness morphology. The difference in slope is due largely to the influence of the roughness parameter (?U+ in the usual notation) and all the data can be fitted empirically by using a modified form of the scaling, dependent only on ?U/Ue. The turbulence intensity, at a location in the outer layer where U/Ue is fixed, rises monotonically with increasing ?U/Ue which, however, remains of O(1) for all possible zero-pressure-gradient rough-wall boundary layers even at the highest Reynolds numbers. A measurement of intensity at a point in the outer region of the boundary layer can provide an indication of whether the surface is aerodynamically fully rough, without having to determine the surface stress or effective roughness height. Discussion of the implication for smooth/rough flow universality of differences in outer-layer mean velocity wake strength is included
0022-1120
119-131
Castro, Ian P.
66e6330d-d93a-439a-a69b-e061e660de61
Segalini, Antoni
99c2765e-2f5e-43f3-a2f2-ef0572052bad
Alfredsson, Henrik
e3e00627-5498-4862-911e-ec78105e8f16
Castro, Ian P.
66e6330d-d93a-439a-a69b-e061e660de61
Segalini, Antoni
99c2765e-2f5e-43f3-a2f2-ef0572052bad
Alfredsson, Henrik
e3e00627-5498-4862-911e-ec78105e8f16

Castro, Ian P., Segalini, Antoni and Alfredsson, Henrik (2013) Outer layer turbulence intensities in smooth- and rough-wall boundary layers. Journal of Fluid Mechanics, 727, 119-131. (doi:10.1017/jfm.2013.252).

Record type: Article

Abstract

Clear differences in turbulence intensity profiles in smooth, transitional and fully rough zero-pressure-gradient boundary layers are demonstrated, using the diagnostic plot introduced by Alfredsson, Segalini & Örlü (Phys. Fluids, vol. 23, 2011, p. 041702) – u?/U versus U/Ue, where u? and U are the local (root mean square) fluctuating and mean velocities and Ue is the free stream velocity. A wide range of published data are considered and all zero-pressure-gradient boundary layers yield outer flow u?/U values that are roughly linearly related to U/Ue, just as for smooth walls, but with a significantly higher slope which is completely independent of the roughness morphology. The difference in slope is due largely to the influence of the roughness parameter (?U+ in the usual notation) and all the data can be fitted empirically by using a modified form of the scaling, dependent only on ?U/Ue. The turbulence intensity, at a location in the outer layer where U/Ue is fixed, rises monotonically with increasing ?U/Ue which, however, remains of O(1) for all possible zero-pressure-gradient rough-wall boundary layers even at the highest Reynolds numbers. A measurement of intensity at a point in the outer region of the boundary layer can provide an indication of whether the surface is aerodynamically fully rough, without having to determine the surface stress or effective roughness height. Discussion of the implication for smooth/rough flow universality of differences in outer-layer mean velocity wake strength is included

Text
RWBL_DiagF.pdf - Author's Original
Download (780kB)

More information

Published date: July 2013
Organisations: Aerodynamics & Flight Mechanics Group

Identifiers

Local EPrints ID: 354304
URI: http://eprints.soton.ac.uk/id/eprint/354304
ISSN: 0022-1120
PURE UUID: 5e9accbc-53df-45f0-b77b-6791ea71c935

Catalogue record

Date deposited: 08 Jul 2013 08:53
Last modified: 20 Nov 2021 15:03

Export record

Altmetrics

Contributors

Author: Ian P. Castro
Author: Antoni Segalini
Author: Henrik Alfredsson

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.

×