The University of Southampton
University of Southampton Institutional Repository

Effect of roughness on wall-bounded turbulence

Effect of roughness on wall-bounded turbulence
Effect of roughness on wall-bounded turbulence
Direct numerical simulation of turbulent incompressible plane-channel flow between a smooth wall and one covered with regular three-dimensional roughness elements is performed. While the impact of roughness on the mean-velocity profile of turbulent wall layers is well understood, at least qualitatively, the manner in which other features are affected, especially in the outer layer, has been more controversial. We compare results from the smooth- and rough-wall sides of the channel for three different roughness heights of h += 5.4, 10.8, and 21.6 for Re ? of 400, to isolate the effects of the roughness on turbulent statistics and the instantaneous turbulence structure at large and small scales. We focus on the interaction between the near-wall and outer-layer regions, in particular the extent to which the near-wall behavior influences the flow further away from the surface. Roughness tends to increase the intensity of the velocity and vorticity fluctuations in the inner layer. In the outer layer, although the roughness alters the velocity fluctuations, the vorticity fluctuations are relatively unaffected. The higher-order moments and the energy budgets demonstrate significant differences between the smooth-wall and rough-wall sides in the processes associated with the wall-normal fluxes of the Reynolds shear stresses and turbulence kinetic energy. The length scales and flow dynamics in the roughness sublayer, the spatially inhomogeneous layer within which the flow is directly influenced by the individual roughness elements, are also examined. Alternative mechanisms involved in producing and maintaining near-wall turbulence in rough-wall boundary layers are also considered. We find that the strength of the inner/outer-layer interactions are greatly affected by the size of the roughness elements.
1386-6184
463-492
Bhaganagar, K.
2d3d055b-c904-4341-b76e-f7b88ae47a19
Kim, J.
21f4bbd0-f650-4fb1-b35c-664a18c05dcd
Coleman, G.
ea3639b9-c533-40d7-9edc-3c61246b06e0
Bhaganagar, K.
2d3d055b-c904-4341-b76e-f7b88ae47a19
Kim, J.
21f4bbd0-f650-4fb1-b35c-664a18c05dcd
Coleman, G.
ea3639b9-c533-40d7-9edc-3c61246b06e0

Bhaganagar, K., Kim, J. and Coleman, G. (2004) Effect of roughness on wall-bounded turbulence. Flow Turbulence and Combustion, 72, 463-492. (doi:10.1023/B:APPL.0000044407.34121.64).

Record type: Article

Abstract

Direct numerical simulation of turbulent incompressible plane-channel flow between a smooth wall and one covered with regular three-dimensional roughness elements is performed. While the impact of roughness on the mean-velocity profile of turbulent wall layers is well understood, at least qualitatively, the manner in which other features are affected, especially in the outer layer, has been more controversial. We compare results from the smooth- and rough-wall sides of the channel for three different roughness heights of h += 5.4, 10.8, and 21.6 for Re ? of 400, to isolate the effects of the roughness on turbulent statistics and the instantaneous turbulence structure at large and small scales. We focus on the interaction between the near-wall and outer-layer regions, in particular the extent to which the near-wall behavior influences the flow further away from the surface. Roughness tends to increase the intensity of the velocity and vorticity fluctuations in the inner layer. In the outer layer, although the roughness alters the velocity fluctuations, the vorticity fluctuations are relatively unaffected. The higher-order moments and the energy budgets demonstrate significant differences between the smooth-wall and rough-wall sides in the processes associated with the wall-normal fluxes of the Reynolds shear stresses and turbulence kinetic energy. The length scales and flow dynamics in the roughness sublayer, the spatially inhomogeneous layer within which the flow is directly influenced by the individual roughness elements, are also examined. Alternative mechanisms involved in producing and maintaining near-wall turbulence in rough-wall boundary layers are also considered. We find that the strength of the inner/outer-layer interactions are greatly affected by the size of the roughness elements.

Text
22687.pdf - Version of Record
Restricted to Repository staff only
Request a copy

More information

Published date: 2004
Organisations: Engineering Sciences

Identifiers

Local EPrints ID: 22687
URI: https://eprints.soton.ac.uk/id/eprint/22687
ISSN: 1386-6184
PURE UUID: ef72fcf0-6aaf-4480-8765-d8e2cbafefa6

Catalogue record

Date deposited: 17 Mar 2006
Last modified: 19 Jul 2019 19:11

Export record

Altmetrics

Contributors

Author: K. Bhaganagar
Author: J. Kim
Author: G. Coleman

University divisions

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 https://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.

×