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Effects of rotation on turbulent mixing across a density interface

Published online by Cambridge University Press:  26 April 2006

M. Fleury ,
M. Mory ,
E. J. Hopfinger  and
D. Auchere
M. Fleury
Affiliation:
Institut de Mécanique de Grenoble, Domaine Universitaire, BP 53X, 38041 Grenoble Cédex, Prance Present address: Chesapeake Bay Institute, The Rotunda, 711W, 40th Street, Baltimore, Md 21211, USA.
M. Mory
Affiliation:
Institut de Mécanique de Grenoble, Domaine Universitaire, BP 53X, 38041 Grenoble Cédex, Prance
E. J. Hopfinger
Affiliation:
Institut de Mécanique de Grenoble, Domaine Universitaire, BP 53X, 38041 Grenoble Cédex, Prance
D. Auchere
Affiliation:
Institut de Mécanique de Grenoble, Domaine Universitaire, BP 53X, 38041 Grenoble Cédex, Prance
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Abstract

The effect of rotation on mixing across a density interface is studied experimentally in a two-layer stratified fluid. Mixing is caused by turbulence produced in one of the layers by an oscillating grid. The flow depends on the Richardson number Ri = g′l/u2 and the Rossby number Ro = u/2Ωl. The most important result is the observed decrease of the entrainment rate E in the presence of rotation, when compared with non-rotating experiments. In a certain range of the two parameters, a general entrainment law in the form E = 0.5RoRi−1 is established, whereas the entrainment law in non-rotating conditions is $E = 1.6 Ri^{-\frac{3}{2}}$. Additional information concerning the dynamics of the interface in rotating conditions is provided by interface displacement spectra, showing that rotation favours low-frequency oscillations of the interface, whereas high-frequency oscillations are not modified by rotation. Finally, the role of inertial waves is discussed on the basis of velocity measurements in the non-stirred layer.

Type
Research Article
Information
Journal of Fluid Mechanics , Volume 223 , February 1991 , pp. 165 - 191
Copyright
© 1991 Cambridge University Press

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