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Published October 10, 2019 | public
Journal Article

Spatial stability analysis of subsonic corrugated jets

Abstract

The linear stability of high-Reynolds-number corrugated jets is investigated by solving the compressible Rayleigh equation linearized about the time-averaged flow field. A Floquet ansatz is used to account for periodicity of this base flow in the azimuthal direction. The origin of multiple unstable solutions, which are known to appear in these non-circular configurations, is traced through gradual perturbations of a parametrized base-flow profile. It is shown that all unstable modes are corrugated jet continuations of the classical Kelvin–Helmholtz modes of circular jets, highlighting that the same instability mechanism, modified by corrugations, leads to the growth of disturbances in such flows. It is found that under certain conditions the eigenvalues may form saddles in the complex plane and display axis switching in their eigenfunctions. A parametric study is also conducted to understand how penetration and number of corrugations impact stability. The effect of these geometric properties on growth rates and phase speeds of the multiple unstable modes is explored, and the results provide guidelines for the development of nozzle configurations that more effectively modify the Kelvin–Helmholtz instability.

Additional Information

© 2019 Cambridge University Press. Received 19 September 2018; revised 14 June 2019; accepted 11 July 2019. F.C.L.J. thanks P. Jordan for fruitful discussions that took place during a six-hour wait in Charles de Gaulle airport. This work was supported by the CAPES PDSE programme (process 88881.135043/2016-01).

Additional details

Created:
August 19, 2023
Modified:
October 18, 2023