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RESTORING ISOTROPIC UNIVERSALITY IN FREELY DECAYING ROTATING TURBULENCE

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We analyse the anisotropy of homogeneous turbulence in a rotating frame. The Zeman scale k_Omega (Zeman, 1994) was introduced to quantify the effect of non-linearity compared to the Coriolis effect, and quantify anisotropy at different scales: at large scales k<<k_Omega the anisotropy created by rotation is dominant, whereas at small scales k_Omega<<k, universal 3D isotropic characteristics of turbulence appear to be restored. We investigate the corresponding phenomenon using Direct Numerical Simulations (DNS) in freely decaying turbulence, varying the rotation rate. We confirm the return to isotropy of the small scales by analyzing the angular power spectrum, the energy transfer and poloidal/toroidal energy modes. The universality is restored at small scales, but for the larger rotation rate case.

Author(s):

DELACHE ALEXANDRE    
Université de Saint-Etienne
France

CAMBON CLAUDE    
CNRS - Ecole Centrale de Lyon
France

GODEFERD Fabien S    
CNRS - Ecole Centrale de Lyon
France