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Coaxial scattering of Euler-equation translating V-states via contour dynamics

Published online by Cambridge University Press:  20 April 2006

Edward A. Overman
Affiliation:
Institute for Computational Mathematics and Applications, Department of Mathematics and Statistics, University of Pittsburgh, Pittsburgh, PA 15261
Norman J. Zabusky
Affiliation:
Institute for Computational Mathematics and Applications, Department of Mathematics and Statistics, University of Pittsburgh, Pittsburgh, PA 15261

Abstract

The robustness of localized states that transport energy and mass is assessed by a numerical study of the Euler equation in two space dimensions. The localized states are the translating ‘V-states’ discovered by Deem & Zabusky. These piecewise- constant dipolar (i.e. oppositely-signed ± or ±) vorticity regions are steady translating solutions of the Euler equations. A new adaptive contour-dynamical algorithm with curvature-controlled node insertion and removal is used. The evolution of one V-state, subject to a symmetric-plus-asymmetric perturbation is examined and stable (i.e. non-divergent) fluctuations are observed. For scattering interactions, coaxial head-on (or ± on ±) and head-tail (or & on ±) arrangements are studied. The temporal variation of contour curvature and perimeter after V-states separate indicate that internal degrees of freedom have been excited. For weak interactions we observe phase shifts and the near recurrence to initial states. When two similar, equal-circulation but unequal-area V-states have a head-on interaction a new asymmetric state is created by contour ‘exchange’. There is strong evidence that this is near to a V-state. For strong interactions we observe phase shifts, ‘breaking’ (filament formation) and, for head-tail interactions, merger of like-signed vorticity regions.

Type
Research Article
Copyright
© 1982 Cambridge University Press

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