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Three-dimensional stability of an elliptical vortex in a straining field

Published online by Cambridge University Press:  20 April 2006

A. C. Robinson
Affiliation:
Applied Mathematics, California Institute of Technology, Pasadena, California 91125 Present address: Sandia National Laboratories, Albuquerque, New Mexico 87185.
P. G. Saffman
Affiliation:
Applied Mathematics, California Institute of Technology, Pasadena, California 91125

Abstract

The three-dimensional linear stability of a rectilinear vortex of elliptical cross-section existing as a steady state in an irrotational straining field is studied numerically in the case of finite strain. It is shown that the instability predicted analytically for weak strain persists for finite strain and that the weak-strain results continue to be quantitatively valid for finite strain. The dependence of the growth rates of the unstable modes on the strain and the axial-disturbance wavelength is discussed. It is also shown that a three-dimensional instability is always more unstable than a two-dimensional instability in the range of parameters of most interest.

Type
Research Article
Copyright
© 1984 Cambridge University Press

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