On the axisymmetric stability of heated supersonic round jets

We perform an inviscid, spatial stability analysis of supersonic, heated round jets with the mean properties assumed uniform on either side of the jet shear layer, modelled here via a cylindrical vortex sheet. Apart from the hydrodynamic Kelvin–Helmholtz (K—H) wave, the spatial growth rates of the a...

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Bibliographic Details
Published in:Proceedings of the Royal Society. A, Mathematical, physical, and engineering sciences Mathematical, physical, and engineering sciences, 2016-04, Vol.472 (2188), p.1-19
Main Author: Samanta, Arnab
Format: Article
Language:English
Subjects:
Acoustic instability
Acoustic modes
Acoustics
Compressibility
Coupled mode theory
Mach number
Shear layers
Sound
Triangles
Vortex sheets
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Summary:We perform an inviscid, spatial stability analysis of supersonic, heated round jets with the mean properties assumed uniform on either side of the jet shear layer, modelled here via a cylindrical vortex sheet. Apart from the hydrodynamic Kelvin–Helmholtz (K—H) wave, the spatial growth rates of the acoustically coupled supersonic and subsonic instability waves are computed for axisymmetric conditions (m = 0) to analyse their role on the jet stability, under increased heating and compressibility. With the ambient stationary, supersonic instability waves may exist for any jet Mach number Mj ≥ 2, whereas the subsonic instability waves, in addition, require the core-to-ambient flow temperature ratio Tj/T0 > 1. We show, for moderately heated jets at Tj/T0 > 2, the acoustically coupled instability modes, once cut on, to govern the overall jet stability with the K—H wave having disappeared into the cluster of acoustic modes. Sufficiently high heating makes the subsonic modes dominate the jet near-field dynamics, whereas the supersonic instability modes form the primary Mach radiation at far field.
ISSN:1364-5021