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The Stability of Swirling Jets
Published online by Cambridge University Press: 25 April 2016
Abstract
The stability of a swirling cylindrical jet of compressible fluid is examined by performing a normal mode analysis and numerically solving the eigenvalue problem. Perturbations of the form f(r)exp[i(ωt-mϕ-kz)] are considered, where f is any fluid variable. Instabilities which are characteristic of both a non-swirling (top-hat) jet and a Rankine vortex are investigated for a particular axial wavenumber.
The vortex instabilities are weak, and are found to remain weak when axial flow is present. The jet instabilities are much stronger, but axial flow is a stabilizing influence. The positive helicity (km > 0) non-axisymmetric modes (m ≠ 0) are stabilized by a small component of azimuthal flow. The axisymmetric mode (m = 0) and the negative helicity non-axisymmetric modes persist in rapidly swirling jets, but with a greatly reduced growth rate.
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- Copyright © Astronomical Society of Australia 1989
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