The effect of flight on a turbulent jet: coherent structure eduction and resolvent analysis
Abstract
We study coherent structures in subsonic turbulent jets subject to a flight stream. A thorough characterisation of the effects of a flight stream on the turbulent field was recently performed by Maia et al. (Phys. Rev. Fluids, vol. 8, 2023, 063902) and fluctuation energy attenuations were observed over a broad range of frequencies and azimuthal wavenumbers. The Kelvin–Helmholtz, Orr and lift-up mechanisms were all shown to be weakened by the flight stream. Here we expand upon that study and model the changes in the dynamics of jets in flight using global resolvent analysis. The resolvent model is found to correctly capture the main effects of the flight stream on the dynamics of coherent structures, which are educed from a large-eddy simulation database using spectral proper orthogonal decomposition. Three modifications of note are: the damping of low-frequency streaky/Orr structures that carry most of the fluctuation energy; a degradation of the low-rank behaviour of the jet in frequencies where modal instability mechanisms are dominant; and a rank decrease at very low Strouhal numbers. The latter effect is underpinned by larger gain separations predicted by the resolvent analysis, due to a reduction in the wavelength of associated flow structures. This leads to a clearer relative dominance of streaky structures generated by the lift-up mechanism, despite the fact that the lift-up mechanism has been weakened with respect to the static jet.
Copyright and License
Copyright © 2024, Cambridge University Press
Funding
This work has received funding from the Clean Sky 2 Joint Undertaking (JU) under the European Union's Horizon 2020 research and innovation programme under grant agreement no. 785303. Results reflect only the authors’ view and the JU is not responsible for any use that may be made of the information it contains. The LES studies were performed at Cascade Technologies and were supported in part by NAVAIR SBIR project with computational resources provided by DoD HPCMP. I.A.M. also acknowledges support from the Science Without Borders program through the CNPq grant no. 200676/2015-6.
Additional details
- European Commission
- 785303
- Accepted
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2024-03-18Accepted
- Available
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2024-04-19Published online
- Publication Status
- Published