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Vorticity organization in the outer layer of turbulent channels with disturbed walls

Published online by Cambridge University Press:  30 October 2007

OSCAR FLORES
Affiliation:
School of Aeronautics, Universidad Politécnica de Madrid, 28040 Madrid, Spain
JAVIER JIMÉNEZ
Affiliation:
School of Aeronautics, Universidad Politécnica de Madrid, 28040 Madrid, Spain Center for Turbulence Research, Stanford University, Stanford, CA 94305, USA
JUAN C. DEL ÁLAMO
Affiliation:
MAE Department, University of California San Diego, La Jolla, CA 92093, USA

Abstract

The vortex clusters in the turbulent outer region of rough- and smooth-walled channels, and their associated velocity structures, are compared using data from numerical experiments at friction Reynolds numbers Reτ ≤ 674. The results indicate that the roughness of the wall does not affect their properties, particularly the existence of wall-detached and wall-attached populations, and the self-similar size distribution of the latter. The average flow field conditioned to the attached clusters reveals similar conical structures of low streamwise velocity for the rough- and smooth-walled cases, which eventually grow into the global modes previously identified from spectral analysis. We conclude that the vortex clusters of the turbulent outer region either originate away from the wall, or quickly forget their origin, in agreement with Townsend's similarity hypothesis.

Type
Papers
Copyright
Copyright © Cambridge University Press 2007

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