Linear and nonlinear mechanisms of sound radiation by instability waves in subsonic jets


Suponitsky, Victoria, Sandham, Neil D. and Morfey, Christopher L. (2010) Linear and nonlinear mechanisms of sound radiation by instability waves in subsonic jets. Journal of Fluid Mechanics, 658, 509-538. (doi:10.1017/S0022112010002375).

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Description/Abstract

Linear and nonlinear mechanisms of sound generation in subsonic jets are investigated by numerical simulations of the compressible Navier–Stokes equations. The main goal is to demonstrate that low-frequency waves resulting from nonlinear interaction between primary, highly amplified, instability waves can be efficient sound radiators in subsonic jets. The current approach allows linear, weakly nonlinear and highly nonlinear mechanisms to be distinguished. It is demonstrated that low-frequency waves resulting from nonlinear interaction are more efficient in radiating sound when compared to linear instability waves radiating directly at the same frequencies. The results show that low-frequency sound radiated predominantly in the downstream direction and characterized by a broadband spectral peak near St = 0.2 can be observed in the simulations and described in terms of the nonlinear interaction model. It is also shown that coherent low-frequency sound radiated at higher angles to the jet axis (θ = 60°–707°) is likely to come from the interaction between two helical modes with azimuthal wavenumbers n = ±1. High-frequency noise in both downstream and side-line directions seems to originate from the breakdown of the jet into smaller structures

Item Type: Article
ISSNs: 0022-1120 (print)
1469-7645 (electronic)
Keywords: aeroacoustics, jet noise, nonlinear instability
Subjects: T Technology > TL Motor vehicles. Aeronautics. Astronautics
Divisions: University Structure - Pre August 2011 > School of Engineering Sciences > Aerodynamics & Flight Mechanics
ePrint ID: 168473
Date Deposited: 30 Nov 2010 10:00
Last Modified: 27 Mar 2014 19:19
Projects:
Jet noise from instability mode interactions
Funded by: EPSRC (EP/E032028/1)
Led by: Neil David Sandham
17 September 2007 to 16 February 2011
URI: http://eprints.soton.ac.uk/id/eprint/168473

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