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Evolution and dynamics of shear-layer structures in near-wall turbulence

Published online by Cambridge University Press:  26 April 2006

Arne V. Johansson
Affiliation:
Department of Mechanics, Royal Institute of Technology, S-100 44 Stockholm, Sweden
P. Henrik Alfredsson
Affiliation:
Department of Mechanics, Royal Institute of Technology, S-100 44 Stockholm, Sweden Present address: Department of Gasdynamics, Royal Institute of Technology, S-10044 Stockholm, Sweden.
John Kim
Affiliation:
NASA Ames Research Center, Moffet Field, CA 94035, USA

Abstract

Near-wall flow structures in turbulent shear flows are analysed, with particular emphasis on the study of their space–time evolution and connection to turbulence production. The results are obtained from investigation of a database generated from direct numerical simulation of turbulent channel flow at a Reynolds number of 180 based on half-channel width and friction velocity. New light is shed on problems associated with conditional sampling techniques, together with methods to improve these techniques, for use both in physical and numerical experiments. The results clearly indicate that earlier conceptual models of the processes associated with near-wall turbulence production, based on flow visualization and probe measurements need to be modified. For instance, the development of asymmetry in the spanwise direction seems to be an important element in the evolution of near-wall structures in general, and for shear layers in particular. The inhibition of spanwise motion of the near-wall streaky pattern may be the primary reason for the ability of small longitudinal riblets to reduce turbulent skin friction below the value for a flat surface.

Information

Type
Research Article
Copyright
© 1991 Cambridge University Press

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