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On the evolution and saturation of instabilities of two-dimensional isolated circular vortices

Published online by Cambridge University Press:  10 June 1999

R. C. KLOOSTERZIEL
Affiliation:
School of Ocean and Earth Science and Technology, University of Hawaii at Manoa, Honolulu, HI 96822, USA
G. F. CARNEVALE
Affiliation:
Scripps Institution of Oceanography, University of California San Diego, La Jolla, CA 92093, USA

Abstract

Laboratory observations and numerical experiments have shown that a variety of compound vortices can emerge in two-dimensional flow due to the instability of isolated circular vortices. The simple geometrical features of these compound vortices suggest that their description may take a simple form if an appropriately chosen set of functions is used. We employ a set which is complete on the infinite plane for vorticity distributions with finite total enstrophy. Through projection of the vorticity equation (Galerkin method) and subsequent truncation we derive a dynamical system which is used to model the observed behaviour in as simple as possible a fashion. It is found that at relatively low-order truncations the observed behaviour is qualitatively captured by the dynamical system. We determine what the necessary ingredients are for saturation of instabilities at finite amplitude in terms of wave–wave interactions and feedback between various azimuthal components of the vorticity field.

Type
Research Article
Copyright
© 1999 Cambridge University Press

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