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| Titel |
An experimental investigation on elliptical instability of a strongly asymmetric vortex pair in a stable density stratification |
| VerfasserIn |
B. Cariteau, J.-B. Flór |
| Medientyp |
Artikel
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| Sprache |
Englisch
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| ISSN |
1023-5809
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| Digitales Dokument |
URL |
| Erschienen |
In: Nonlinear Processes in Geophysics ; 13, no. 6 ; Nr. 13, no. 6 (2006-11-20), S.641-649 |
| Datensatznummer |
250011873
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| Publikation (Nr.) |
 copernicus.org/npg-13-641-2006.pdf |
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| Zusammenfassung |
| We investigate the elliptical instability of a strongly asymmetric vortex
pair in a stratified fluid, generated by the acceleration and deceleration of
the rotation of a single flap. The dominant parameter is the Froude number,
Fr=U/(NR), based on the maximum azimuthal velocity, U, and
corresponding radius, R, of the strongest vortex, i.e. the principal vortex,
and buoyancy frequency N. For Fr>1, both vortices are elliptically
unstable while the instability is suppressed for Fr<1. In an asymmetric
vortex pair, the principal vortex is less – and the secondary vortex more –
elliptical than the vortices in an equivalent symmetric dipolar vortex. The
far more unstable secondary vortex interacts with the principal vortex and
increases the strain on the latter, thus increasing its ellipticity and its
instability growth rate. The nonlinear interactions render the elliptical
instability more relevant. An asymmetric dipole can be more unstable than an
equivalent symmetric dipole. Further, the wavelength of the instability is
shown to be a function of the Froude number for strong stratifications
corresponding to small Froude numbers, whereas it remains constant in the
limit of a homogenous fluid. |
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