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Strong interactions between two corotating quasi-geostrophic vortices

Published online by Cambridge University Press:  14 November 2007

ROSS R. BAMBREY
Affiliation:
Mathematical Institute, University of St Andrews, North Haugh, St Andrews, Fife KY16 9SS, UK
JEAN N. REINAUD
Affiliation:
Mathematical Institute, University of St Andrews, North Haugh, St Andrews, Fife KY16 9SS, UK
DAVID G. DRITSCHEL
Affiliation:
Mathematical Institute, University of St Andrews, North Haugh, St Andrews, Fife KY16 9SS, UK

Abstract

In this paper we investigate the interaction between two corotating quasi-geostrophic vortices. The initially ellipsoidal vortices are separated horizontally by a distance corresponding to the margin of stability, as determined from an ellipsoidal analysis. The subsequent interaction depends on four parameters: the vortex volume ratio, the vertical centroid separation, and the height-to-width aspect ratios of each vortex. The most commonly observed strong interaction is partial merger, where only part of the weaker vortex is incorporated into the stronger one or cast into filamentary debris. Despite the proliferation of small-scale filamentary structure during many vortex interactions, on average the self-induced vortex energy exhibits an ‘inverse cascade’ to larger scales, broadly consistent with spectral theories of turbulence. Curiously, we observe that a range of intermediate-scale vortices are preferentially sheared out during the interactions, leaving two main populations of large and small vortices.

Type
Papers
Copyright
Copyright © Cambridge University Press 2007

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