Laboratoire de Mécanique des Fluides et d'Acoustique - UMR 5509

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Laboratoire de Mécanique des Fluides et d’Acoustique
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Accueil > Équipes > Turbulence & Instabilités > Publications T&I et posters doctorants > Publications T&I 2021

Article dans Phys. Rev. E (2021)

Spontaneous generation and reversal of helicity in anisotropic turbulence

Wesley Agoua, Benjamin Favier, Alexandre Delache, Antoine Briard & Wouter Bos

Spontaneous generation and reversal of helicity in anisotropic turbulence

Helicity plays an important role in spectacular geophysical phenomena such as hurricanes or the generation of the terrestrial magnetic field. The present investigation shows how helicity can be created in a statistically homogeneous but anisotropic flow, driven by buoyancy. If the flow is close enough to a two-dimensional limit, spontaneous symmetry breaking leads to the generation of mean helicity. In particular, we explain these observations by identifying a simple linear mechanism, the relevance of which is illustrated by simulations of unstably stratified turbulence in a conducting fluid on which a magnetic field is imposed. Finally it is shown that the self-organized state displays dynamical reversals of the sign of the mean helicity.

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