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Pulsating turbulence in a marginally unstable stratified shear flow

Published online by Cambridge University Press:  01 June 2017

W. D. Smyth Open the ORCID record for W. D. Smyth [Opens in a new window] ,
H. T. Pham ,
J. N. Moum  and
S. Sarkar Open the ORCID record for S. Sarkar [Opens in a new window]
W. D. Smyth*
Affiliation:
College of Earth, Ocean and Atmospheric Sciences, Oregon State University, Corvallis, OR 97330, USA
H. T. Pham
Affiliation:
Department of Mechanical and Aerospace Engineering, University of California, San Diego, CA 92093, USA
J. N. Moum
Affiliation:
College of Earth, Ocean and Atmospheric Sciences, Oregon State University, Corvallis, OR 97330, USA
S. Sarkar
Affiliation:
Department of Mechanical and Aerospace Engineering, University of California, San Diego, CA 92093, USA
*
†Email address for correspondence: smythw@oregonstate.edu
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Abstract

We describe a simple model for turbulence in a marginally unstable, forced, stratified shear flow. The model illustrates the essential physics of marginally unstable turbulence, in particular the tendency of the mean flow to fluctuate about the marginally unstable state. Fluctuations are modelled as an oscillatory interaction between the mean shear and the turbulence. The interaction is made quantitative using empirically established properties of stratified turbulence. The model also suggests a practical way to estimate both the mean kinetic energy of the turbulence and its viscous dissipation rate. Solutions compare favourably with observations of fluctuating ‘deep cycle’ turbulence in the equatorial oceans.

JFM classification

Geophysical and Geological Flows: Air/sea interactions Turbulent Flows: Shear layer turbulence Turbulent Flows: Stratified turbulence
Type
Papers
Information
Journal of Fluid Mechanics , Volume 822 , 10 July 2017 , pp. 327 - 341
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Copyright
© 2017 Cambridge University Press 

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