Transmission of sound through a two-dimensional shielding jet

Cowan, S.; Crouch, Robert W.

doi:10.2514/6.1973-1002

Cited by 15 publications

(4 citation statements)

References 1 publication

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“…New concepts such as asymmetric or beveled nozzles have been investigated [10,11] to create asymmetric flow fields that modify shock structures and shear layer mixing. Thermal acoustic fluid shielding [12,13,14], involving addition of a second heated stream on the nozzle perimeter to trap high frequency noise generation inside the jet plume, has also been investigated. Recent studies using this concept routed engine bypass air to a semi-annular fluid shield on the underside of the engine [5].…”

Section: Motivationmentioning

confidence: 99%

Towards Prediction and Control of Large Scale Turbulent Structure Supersonic Jet Noise

Schlinker¹,

Reba²,

Simonich³

et al. 2009

Volume 1: Aircraft Engine; Ceramics; Coal, Biomass and Alternative Fuels; Controls, Diagnostics and Instrumentation; Education;

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In this paper, we report on progress towards developing physics-based models of sound generation by large-scale turbulent structures in supersonic jet shear layers generally accepted to be the source of aft-angle noise. Aside from obtaining better engineering prediction schemes, the development and optimization of long term jet noise reduction strategies based on controlling instability wave generated large-scale turbulence structures in the shear layer can be more successful if based on predictive flow-noise models, rather than on build and test approaches alone. Such models, if successful, may also provide a path by which laboratory scale demonstrations can be more reliably translated to engine scale. Results show that the noise radiated by large-scale structures in turbulent jet shear layers may be modeled using a RANS based PSE method and projected to the far-field using a Kirchhoff surface approach. A key enabler in this procedure is the development of near-field microphone arrays capable of providing the pressure statistics needed to validate the instability wave models. Our framework provides, for the first time, a deterministic model that will allow understanding and predicting noise radiated by large-scale turbulence.

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Section: Motivationmentioning

confidence: 99%

Towards Prediction and Control of Large Scale Turbulent Structure Supersonic Jet Noise

Schlinker¹,

Reba²,

Simonich³

et al. 2009

Volume 1: Aircraft Engine; Ceramics; Coal, Biomass and Alternative Fuels; Controls, Diagnostics and Instrumentation; Education;

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“…. (1) where x 0 is an apparent shift in the flow origin due to nozzle outlet conditions. The axial centre-line velocity decay is given by the expression:…”

Section: Theoretical Considerationsmentioning

confidence: 99%

The flow development in a shielding jet

Baker

1984

Aeronaut. j.

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SummaryThe flow from a high aspect ratio rectangular nozzle has been studied, so as to provide data to aid prediction of the effectiveness of this type of jet flow for acoustic shielding. Flow parameters investigated in both stationary and parallel, coflowing, airstreams, include axial centre-line velocity decay, jet width growth and velocity profile similarity. The existence of significant velocity peaks towards the edge of the jet in the plane of the major axis was observed, together with an unexpected interaction on this jet flow by an adjacent circular and subsonic jet.

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“…The peak jet noise source moves upstream and radiates noise at larger angles to the flow direction. 8 Noise radiation from a source can be shielded by an adjacent jet, as was recognized in the 1970s [9][10][11] where early work focused on engine arrangement studies. The governing mechanisms for shielding are refraction and diffraction of sound by the jet flow.…”

Section: Introductionmentioning

confidence: 97%

Acoustic characteristics of twin jets

Zhang

2002

The Journal of the Acoustical Society of America

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Experiments were conducted to investigate the acoustic characteristics of underexpanded supersonic twin jets in different azimuthal measurement planes. Compared with two independent jets, the twin jets produced additional noise due to the enhanced mixing and entrainment. The larger pressure ratio for switching from the axisymmetric mode to the helical mode led to lower noise levels at 90 degrees than for two independent jets. For pressure ratios greater than 5.00, the noise reduction was due to cessation of screeching of the twin jets while screeching of a single jet was still detected. The apparent shielding phenomenon was measured for the screech helical mode. The screech tone intensities were attenuated largely due to the shielding effects. The noise reductions due to shielding were obtained over a wide range of pressure ratios relative to the sum of two independent jets.

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Transmission of sound through a two-dimensional shielding jet

Cited by 15 publications

References 1 publication

Towards Prediction and Control of Large Scale Turbulent Structure Supersonic Jet Noise

Towards Prediction and Control of Large Scale Turbulent Structure Supersonic Jet Noise

The flow development in a shielding jet

Acoustic characteristics of twin jets

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