TY - JOUR
T1 - Upstream-travelling acoustic jet modes as a closure mechanism for screech
AU - Edgington-Mitchell, Daniel
AU - Jaunet, Vincent
AU - Jordan, Peter
AU - Towne, Aaron
AU - Soria, Julio
AU - Honnery, Damon
PY - 2018/11/25
Y1 - 2018/11/25
N2 - 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.
AB - 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.
KW - compressible flows
KW - jet noise
KW - shock waves
UR - http://www.scopus.com/inward/record.url?scp=85054993131&partnerID=8YFLogxK
U2 - 10.1017/jfm.2018.642
DO - 10.1017/jfm.2018.642
M3 - Article
AN - SCOPUS:85054993131
SN - 0022-1120
VL - 855
JO - Journal of Fluid Mechanics
JF - Journal of Fluid Mechanics
M1 - R1
ER -