Wing shielding of high-velocity jet and shock-associated noise with cold and hot flow jets

Glahn, U. Von; Groesbeck, D.; Wagner, J. M.

doi:10.2514/6.1976-547

Cited by 7 publications

(5 citation statements)

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“…Whether the aircraft are powered by turbofan or open-rotor engines, the noise reduction goals are unlikely to be met without exploiting the propulsion-airframe integration that will reduce the noise emitted towards the community. The advent of the Hybrid Wing-Body (HWB) airplane 1 , with the engines mounted over the wing, has reinvigorated the engine overthe-wing (OTW) concept for noise shielding, an area of active research in the 1970s [2][3][4] . The HWB design allows sufficient planform area for shielding of both the forward-emitting turbomachinery sources and the aft-emitting jet noise sources.…”

Section: Introductionmentioning

confidence: 99%

Jet Noise Shielding for Advanced Hybrid Wing-Body Configuration

Papamoschou

Mayoral

2011

49th AIAA Aerospace Sciences Meeting Including the New Horizons Forum and Aerospace Exposition

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We present an experimental study of jet noise shielding with an advanced design for the Hybrid Wing-Body airplane. The design, called N2AEXTE, features an extended trailing edge over its predecessor, the N2A. Static acoustic tests were conducted at a scale factor of 90 with realistic exhaust conditions of a bypass ratio 10 nozzle. The acoustic data show cumulative (downward +sideline) EPNL reductions of up to 10 dB with the nozzle at its nominal position and up to 13 dB with the nozzle traversed upstream by one fan diameter. These reductions are 2-3 dB better than with the basic N2A design. Redistribution of the jet noise source and incorporation of inboard vertical fins are essential elements for achieving those reductions. Devices used to alter the jet noise source comprised aggressive chevrons, a porous wedge fan flow deflector, and their combination. Two shapes for the vertical fins were tested-a nominal design and an alternate design featuring longer chord and shorter height. The alternate fin design offered slight noise benefits.

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Section: Introductionmentioning

confidence: 99%

Jet Noise Shielding for Advanced Hybrid Wing-Body Configuration

Papamoschou

Mayoral

2011

49th AIAA Aerospace Sciences Meeting Including the New Horizons Forum and Aerospace Exposition

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“…The data shown are for a 9.5 cm diameter nozzle operated with a nominal pressure ratio of 2.75 (ref. 10). Screech tones are generally omni-directional so that screech-tone data obtained a4 one directivity angle are similar to those; at different angles.…”

Section: Backgroun1?mentioning

confidence: 96%

New interpretations of shock-associated noise with and without screech

Glahn

1980

The Journal of the Acoustical Society of America

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SUMMARYAnomalous trends in present convergent nozzle (Mach 1) shock-associated noise analyses and predictions, with parttoular znphasis on the roles of screech and ,jet temperature, are discussed. Experimentally measured values of shock-associated noise are usedto reassess data trends, including both frequency and sound pressure level. The data used Includes model-scale o% nozzles, varying in nominal diameter from 5 cm to 13 cm, and Cull-scale engine nozzles up to 48 cm. All data were obtained at static conditions. From this sM reassessment of the measured data, now empirical methods for the prediction of shock-associated noise are developed. Separate procedures are presented for screech-free and screech-contaminated shock-asnociatod noise. In the present approach, shock-associated noise spectra are developed from considerations thatInclude the peak sound pressure Level and its frequency, the loan frequency sound pressure level slope, and the high frequency ;sound pressure level, slape or roll-off; the latter is shown to vary with directivity angle.

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“…1,2 These calculations showed extremely high efficiency of the engine noise shielding. It gave a stimulus to a works which was dedicated to the search of the general arrangement for airplanes with airframe structures shielding noise of the aviation engine.…”

Section: Introductionmentioning

confidence: 97%

Airframe Shielding of Noncompact Aviation Noise Sources: Theory and Experiment

Ostrikov¹,

Denisov²

2015

21st AIAA/CEAS Aeroacoustics Conference

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In the present work we investigate the effect of noncompactness of aviation noise sources on airframe shielding. Performed experimental results showed what shielding effect is very sensitive to the type of source and geometrical features of the shielding surface. For example, the features of rotor tonal noise and rotor broadband noise shielding are differed. In the present work we seek for the theoretical methods for correct predicting of shielding effect for noncompact sources, Fresnel/Kirchhoff methods and Geometry Theory of Diffraction (GTD) are under consideration together with some exact solutions. GTD shows the optimal results as compared with other theories for calculating shielding efficiency in the case of noncompact sources calculation. If GTD is applied to shielding effect for noncompact sources generating rotating azimuthal modes (fan tonal noise), then some interesting features are appeared such as the loss of symmetry, the strong dependence of shielding field on the number of azimuthal mode, existence of directions, in which sound emission is considerably amplified.

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Wing shielding of high-velocity jet and shock-associated noise with cold and hot flow jets

Cited by 7 publications

References 0 publications

Jet Noise Shielding for Advanced Hybrid Wing-Body Configuration

Jet Noise Shielding for Advanced Hybrid Wing-Body Configuration

New interpretations of shock-associated noise with and without screech

Airframe Shielding of Noncompact Aviation Noise Sources: Theory and Experiment

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