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Inviscid evolution of stretched vortex arrays

Published online by Cambridge University Press:  21 April 2006

D. I. Pullin
Affiliation:
Department of Mechanical Engineering, University of Queensland, St Lucia, 4067, Australia
P. A. Jacobs
Affiliation:
Department of Mechanical Engineering, University of Queensland, St Lucia, 4067, Australia

Abstract

The nonlinear evolution of an array of pairs of inviscid counter-rotating vortices, subjected to an applied stretching strain field, has been studied numerically using the contour-dynamics method. The array configuration is effectively the Corcos-Lin model of streamwise vortices in the braid region of a nominally two-dimensional mixing layer. For each individual vortex the simulations elucidate the strong interaction between the vortex self-induction, the vorticity amplification of the stretching strain, and the local in-plane strain applied by all other members of the array. When the initial vorticity distribution is modelled by a non-uniform piece-wise-constant vorticity field defined over a nested set of non-intersecting contours, the dynamical evolution reveals fine structure consisting of strong vortex roll-up accompanied by trailing, filament-like spiral vortex sheets, and the presence of tertiary instabilities. It is shown by a particular example that these features are largely absent in an equivalent computation in which array members are modelled by the commonly used uniform-vortex approximation.

Type
Research Article
Copyright
© 1986 Cambridge University Press

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