Instabilities of a columnar vortex in a stratified fluid
Résumé
In this paper, we show that the presence of a vertical density gradient can
destabilise a Gaussian vortex in two different ways. First, when the vortex axis is
slightly tilted with respect to the vertical and if its Froude number is larger than one,
the vortex exhibits strong axial flows inside a critical layer, which lead to a violent
three-dimensional instability. Second, when the vortex axis is vertical, the vortex is
weakly unstable by emission of internal gravity waves. Theoretical predictions for
both instabilities are compared with experimental evidences.
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