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The autonomous cycle of near-wall turbulence

Published online by Cambridge University Press:  25 June 1999

JAVIER JIMÉNEZ
Affiliation:
School of Aeronautics, Universidad Politécnica, 28040 Madrid, Spain Centre for Turbulent Research, Stanford University, Stanford, CA 94305, USA
ALFREDO PINELLI
Affiliation:
School of Aeronautics, Universidad Politécnica, 28040 Madrid, Spain

Abstract

Numerical experiments on modified turbulent channels at moderate Reynolds numbers are used to differentiate between several possible regeneration cycles for the turbulent fluctuations in wall-bounded flows. It is shown that a cycle exists which is local to the near-wall region and does not depend on the outer flow. It involves the formation of velocity streaks from the advection of the mean profile by streamwise vortices, and the generation of the vortices from the instability of the streaks. Interrupting any of those processes leads to laminarization. The presence of the wall seems to be only necessary to maintain the mean shear. The generation of secondary vorticity at the wall is shown to be of little importance in turbulence generation under natural circumstances. Inhibiting its production increases turbulence intensity and drag.

Type
Research Article
Copyright
© 1999 Cambridge University Press

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