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Turbulent/non-turbulent interfaces in wakes in stably stratified fluids

Published online by Cambridge University Press:  16 May 2016

Tomoaki Watanabe*
Affiliation:
Department of Mechanical Engineering, University of Washington, Seattle, WA 98195, USA Department of Aerospace Engineering, Nagoya University, Nagoya 464-8603, Japan
James J. Riley
Affiliation:
Department of Mechanical Engineering, University of Washington, Seattle, WA 98195, USA
Stephen M. de Bruyn Kops
Affiliation:
Department of Mechanical and Industrial Engineering, University of Massachusetts Amherst, Amherst, MA 01003-9284, USA
Peter J. Diamessis
Affiliation:
School of Civil and Environmental Engineering, Cornell University, Ithaca, NY 14853, USA
Qi Zhou
Affiliation:
Department of Applied Mathematics and Theoretical Physics, University of Cambridge, Cambridge CB3 0WA, UK
*
Email address for correspondence: [email protected]

Abstract

We report on a study, employing direct numerical simulations, of the turbulent/non-turbulent interface of a wake in a stably stratified fluid. It is found that thresholds for both enstrophy and potential enstrophy are needed to identify the interface. Using conditional averaging relative to the location of the interface, various quantities of interest are examined. The thickness of the interface is found to scale with the Kolmogorov scale. From an examination of the Ozmidov and Kolmogorov length scales as well as the buoyancy Reynolds number, it is found that the buoyancy Reynolds number decreases and becomes of order 1 near the interface, indicating the suppression of the turbulence there by the stable stratification. Finally the overall rate of loss of energy due to internal wave radiation is found to be comparable to the overall rate of loss due to turbulent kinetic energy dissipation.

Type
Rapids
Copyright
© 2016 Cambridge University Press 

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