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Which scales are more anisotropic in rotating turbulence?

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Basic scaling arguments suggest that anisotropy in rotating turbulence is more pronounced at large scales. However, some
experiments and simulations have revealed a stronger anisotropy at small scales, close to either the Zeman or the Kolmogorov scale.
Using particle image velocimetry measurements of decaying grid turbulence under rotation, we propose that the relevant Rossby number
which governs the scale of maximum anisotropy should be constructed on the two inviscid invariants of rotating turbulence, energy and
helicity. This new Rossby number allows us to explain the concentration of anisotropy at small scales observed in our experiments.

Author(s):

Pierre-Philippe Cortet    
Laboratoire FAST, CNRS, Université Paris-Sud, UPMC
France

Frédéric Moisy    
Laboratoire FAST, CNRS, Université Paris-Sud, UPMC
France