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On convection velocities in turbulent shear flows

Published online by Cambridge University Press:  28 March 2006

J. A. B. Wills
J. A. B. Wills
Affiliation:
National Physical Laboratory, Teddington, Middlesex
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Abstract

The problem of defining an effective velocity of convection for turbulent fluctuations in a shear flow is considered, and the definitions adopted by various workers are discussed. An experiment in the shear layer of a circular jet has shown that the usual definitions, based on peaks of the space-time correlations of the fluctuations, yield convection velocities whose magnitudes depend on the value of space or time separation chosen. An alternative approach shows that, by considering the turbulent field as a superposition of harmonic travelling waves, a wave-number/velocity spectrum can be defined that lends itself to the definition of a wave-number-dependent convection velocity and an overall convection velocity, both of which have real physical significance. An experimental technique is described for obtaining the spectrum, and results are presented for one position in the shear layer of the jet.

Type
Research Article
Information
Journal of Fluid Mechanics , Volume 20 , Issue 3 , November 1964 , pp. 417 - 432
Copyright
© 1964 Cambridge University Press

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