Upstream-travelling acoustic jet modes as a closure mechanism for screech

Abstract : Experimental evidence is provided to demonstrate that the upstream-travelling waves in two jets screeching in the A1 & A2 modes are not freestream acoustic waves but rather waves with support within the jet. Proper Orthogonal Decomposition is used to educe the coherent fluctuations associated with jet screech from a set of randomly sampled velocity fields. A streamwise Fourier transform is then used to isolate components with positive and negative phase speeds. The component with negative phase speed is shown, by comparison with a vortex-sheet model, to resemble the upstream-travelling jet wave first studied by Tam & Hu (1989). It is further demonstrated that screech tones are only observed over the frequency range where this upstream-travelling wave is propagative.
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Submitted on : Wednesday, November 6, 2019 - 2:40:00 PM
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Daniel Edgington-Mitchell, Vincent Jaunet, Peter Jordan, Aaron Towne, Julio Soria, et al.. Upstream-travelling acoustic jet modes as a closure mechanism for screech. Journal of Fluid Mechanics, Cambridge University Press (CUP), 2018, 855, pp.R1. ⟨10.1017/jfm.2018.642⟩. ⟨hal-02351577⟩



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