The University of Southampton
University of Southampton Institutional Repository

The critical Reynolds number for rough-wall boundary layers

The critical Reynolds number for rough-wall boundary layers
The critical Reynolds number for rough-wall boundary layers
Rough-wall boundary layers become aerodynamically smooth if the ‘roughness Reynolds number’ Re*=u*z0/? becomes sufficiently small. Conventional wisdom is that Re* should exceed at least two and perhaps be as much as five before viscous effects are insignificant. This criterion is assessed for the types of rough wall commonly used in laboratory simulations of atmospheric boundary layers—arrays of sharp-edged obstacles with significant separation between each obstacle. It is demonstrated that for such surfaces the roughness length z0 remains constant for falling roughness Reynolds numbers down to at least Re*=1. Viscous effects are shown to change the near-wall Reynolds stresses only for Re* below similar values, so that z0-scaling (rather than scaling based on ?/u*) remains appropriate down to at least Re*=1. One of the practical implications of this result is that wind-tunnel simulations of atmospheric boundary layers can be successful at lower wind speeds (or with smaller roughness elements) than previously supposed.
0167-6105
41-54
Snyder, William
23664694-f462-4cba-a9f7-52c9a632fde3
Castro, Ian P.
66e6330d-d93a-439a-a69b-e061e660de61
Snyder, William
23664694-f462-4cba-a9f7-52c9a632fde3
Castro, Ian P.
66e6330d-d93a-439a-a69b-e061e660de61

Snyder, William and Castro, Ian P. (2002) The critical Reynolds number for rough-wall boundary layers. Journal of Wind Engineering and Industrial Aerodynamics, 90 (1), 41-54. (doi:10.1016/S0167-6105(01)00114-3).

Record type: Article

Abstract

Rough-wall boundary layers become aerodynamically smooth if the ‘roughness Reynolds number’ Re*=u*z0/? becomes sufficiently small. Conventional wisdom is that Re* should exceed at least two and perhaps be as much as five before viscous effects are insignificant. This criterion is assessed for the types of rough wall commonly used in laboratory simulations of atmospheric boundary layers—arrays of sharp-edged obstacles with significant separation between each obstacle. It is demonstrated that for such surfaces the roughness length z0 remains constant for falling roughness Reynolds numbers down to at least Re*=1. Viscous effects are shown to change the near-wall Reynolds stresses only for Re* below similar values, so that z0-scaling (rather than scaling based on ?/u*) remains appropriate down to at least Re*=1. One of the practical implications of this result is that wind-tunnel simulations of atmospheric boundary layers can be successful at lower wind speeds (or with smaller roughness elements) than previously supposed.

This record has no associated files available for download.

More information

Published date: 2002

Identifiers

Local EPrints ID: 22168
URI: http://eprints.soton.ac.uk/id/eprint/22168
ISSN: 0167-6105
PURE UUID: 17a3da92-54e5-4ff6-8d4c-81b72ae628a5

Catalogue record

Date deposited: 20 Mar 2006
Last modified: 15 Mar 2024 06:35

Export record

Altmetrics

Contributors

Author: William Snyder
Author: Ian P. Castro

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.

×