Elliptical Instability in Rotating Von-Karman Street
Abstract
Clouds often reveal a meso-scale vortex shedding in the wake of mountainous islands. Unlike the classical bi-dimensional Von-Karman street, these observed vortex street are affected by the earth rotation and vertical stratification. Theses effects could induce a selective destabilisation of anticyclonic vortices. It is well known that inertial instability (also called centrifugal instability) induce a three-dimensional destabilisation of anticyclonic structures when the absolute vorticity is larger than the local Coriolis parameter. However, we have shown, by the mean of laboratory experiments, that it is a different type of instability which is mainly responsible for asymmetric rotating Von-Karman street. A serie of experiments were performed to study the wake of a cylinder in a rotating fluid, at medium Reynolds number and order one Rossby number. We have shown that the vertical structure of unstable anticyclonic vortices is characteristic of an elliptical instability. Besides, unlike the inertial instability, the vertical unstable wavelength depends on the Rossby number.
- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2001
- Bibcode:
- 2001AGUFMNG42A0403S
- Keywords:
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- 3220 Nonlinear dynamics;
- 3329 Mesoscale meteorology;
- 3379 Turbulence