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

Daniel Edgington-Mitchell | Zendy; Vincent Jaunet | Zendy; Peter Jordan | Zendy; Aaron Towne | Zendy; Julio Soria | Zendy; Damon Honnery | Zendy

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

Author(s) -

Daniel Edgington-Mitchell,

Vincent Jaunet,

Peter Jordan,

Aaron Towne,

Julio Soria,

Damon Honnery

Publication year - 2018

Publication title -

journal of fluid mechanics

Language(s) - English

Resource type - Journals

SCImago Journal Rank - 1.72

H-Index - 226

eISSN - 1469-7645

pISSN - 0022-1120

DOI - 10.1017/jfm.2018.642

Subject(s) - jet (fluid) , physics , vortex , upstream (networking) , acoustics , mechanics , fourier transform , phase (matter) , engineering , telecommunications , quantum mechanics

Experimental evidence is provided to demonstrate that the upstream-travelling waves in two jets screeching in the A1 and A2 modes are not free-stream 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 (J. Fluid Mech., vol. 201, 1989, pp. 447–483). 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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