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

Daniel Edgington-Mitchell, Vincent Jaunet, Peter Jordan, Aaron Towne, Julio Soria, Damon Honnery

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22 Citations (Scopus)

Abstract

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.

Original languageEnglish
Article numberR1
Number of pages12
JournalJournal of Fluid Mechanics
Volume855
DOIs
Publication statusPublished - 25 Nov 2018

Keywords

  • compressible flows
  • jet noise
  • shock waves

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