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Decaying grid turbulence in a rotating stratified fluid

Praud, Olivier and Sommeria, Joël and Fincham, Adam M. Decaying grid turbulence in a rotating stratified fluid. (2006) Journal of Fluid Mechanics, vol. 547 . pp. 389-412. ISSN 0022-1120

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Official URL: http://dx.doi.org/10.1017/S0022112005007068

Abstract

Rotating grid turbulence experiments have been carried out in a stably stratified fluid for relatively large Reynolds numbers (mesh Reynolds numbers up to 18000). Under the combined effects of rotation and stratification the flow degenerates into quasihorizontal motions. This regime is investigated using a scanning imaging velocimetry technique which provides time-resolved velocity fields in a volume. The most obvious effect of rotation is the inhibition of the kinetic energy decay, in agreement with the quasi-geostrophic model which predicts the absence of a direct energy cascade, as found in two-dimensional turbulence. In the regime of small Froude and Rossby numbers, the dynamics is found to be non-dissipative and associated with a symmetric and highly intermittent vertical vorticity field, that displays k(h)(-3) energy spectra. For higher Rossby numbers, fundamental differences with the quasi-geostrophic model are found. A significant decay of kinetic energy, which does not depend on the stratification, is observed. Moreover, in this regime, although both cyclones and anticyclones are initially produced, the intense vortices are only cyclones. For late times the flow consists of an assembly of coherent interacting Structures. Under the influence of both rotation and stratification, they take the form of lens-like eddies with aspect ratio proportional to f/N.

Item Type:Article
Additional Information:Thanks to Cambridge University Press (CUP) editor. The definitive version is available at http://journals.cambridge.org/action/displayAbstract?fromPage=online&aid=371353
Audience (journal):International peer-reviewed journal
Uncontrolled Keywords:
Institution:French research institutions > Centre National de la Recherche Scientifique - CNRS
Other partners > Institut National Polytechnique de Grenoble (FRANCE)
Other partners > Université Joseph Fourier Grenoble 1 - UJF (FRANCE)
Other partners > Université de Grenoble (FRANCE)
Laboratory name:
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Deposited By: Olivier PRAUD

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