Experiments on Shielding of Jet Noise by Airframe Surfaces

Papamoschou, Dimitri; Mayoral, Salvador

doi:10.2514/6.2009-3326

Cited by 29 publications

(13 citation statements)

References 9 publications

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“…The microphone array consists of twenty four 3.2-mm condenser microphones (Bruel & Kjaer, Model 4138). This is a significant enhancement to our previous setup that utilized only eight microphones 5 . For acoustic surveys, the microphones were arranged with twelve on a downward arm (azimuth angle =0 o ) and twelve on a sideline arm (azimuth angle =60 o ).…”

Section: B Aeroacoustic Testingmentioning

confidence: 88%

“…Details of the PNL and EPNL calculation procedure can be found in Ref. 5. The reduction in EPNL (ΔEPNL) is used as a preliminary "figure of merit" in the assessment of jet noise shielding.…”

Section: B Aeroacoustic Testingmentioning

confidence: 99%

“…The HWB design in principle provides sufficient planform area to shield both the forward-emitting turbomachinery noise and the aft-emitting jet noise. Subscale experiments in our laboratory were the first to assess the potential for the HWB planform to shield jet noise 5 . It was found that jet noise shielding was marginal unless the noise source was altered using devices such as chevrons or fan flow deflectors.…”

Section: Introductionmentioning

confidence: 99%

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Effects of Source Redistribution on Jet Noise Shielding

Mayoral

Papamoschou

2010

48th AIAA Aerospace Sciences Meeting Including the New Horizons Forum and Aerospace Exposition

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The potential of jet noise shielding from the Hybrid Wing Body (HWB) airplane is investigated in subscale experiments. The jet nozzle had a bypass ratio 10 and was operated at realistic takeoff exhaust conditions using helium-air mixtures. The shield, fabricated from a thin flat plate, had the generic shape of the HWB planform. Redistribution of the jet noise source is essential for achieving substantial noise reduction. Devices used to alter the jet noise source comprised chevrons (in mild and aggressive configurations) and a number of porous wedge fan flow deflectors. Using the estimated cumulative (downward plus sideline) EPNL reduction as a figure of merit, shielding of the plain nozzle yields a 2.4 dB reduction. Application of the aggressive chevrons increases the reduction to 6.5 dB, while the best wedge configuration improves this figure to 6.9 dB. Combination of wedge and aggressive chevrons yields a benefit of 7.6 dB. Examination of high-definition noise source maps shows a direct link between the insertion loss and the axial location of peak noise source. The aggressive chevrons cause an abrupt contraction of the noise source length at Strouhal number Sr=1.2, while the wedge induces a gradual contraction with increasing frequency. As a result, the insertion loss with the aggressive chevrons is stronger than with the wedge. However, because the wedge is inherently quieter than the chevrons, it gives a slightly better overall benefit. Surveys of the mean flow field show that the wedge, and its combination with chevrons, produces a significant reduction in the potential core length. On the other hand, the chevrons alone induce modest changes in the length of the high-speed region of the jet. Therefore, the mean velocity field by itself cannot provide useful information for inferring the noise source length for these complicated flows.

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Section: B Aeroacoustic Testingmentioning

confidence: 88%

Section: B Aeroacoustic Testingmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Effects of Source Redistribution on Jet Noise Shielding

Mayoral

Papamoschou

2010

48th AIAA Aerospace Sciences Meeting Including the New Horizons Forum and Aerospace Exposition

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“…In the current century, experimental and theoretical investigations were performed for clarifying features of shielding effect. [4][5][6][7][8][9] In particularly, recent experiments showed that the effectiveness of shielding effect is substantially smaller then predicted in some early works. 4,5 In theoretical works the applications of different diffraction methods were under consideration also, however, the shielding effect was mainly considered for point sources.…”

Section: Introductionmentioning

confidence: 99%

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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“…Additionally, the use of an aerospike nozzle would result in configurations that efficiently utilize the entire back area of a rectangular vehicle body to minimize the aftbody base drag. Another advantage of the aerospike nozzle is its low noise generation as has been demonstrated in the aircraft applications using a plug nozzle (Papamoschou and Mayoral, 2009) configuration.…”

Section: Introductionmentioning

confidence: 99%

Conceptual study of supersonic transports employing airframe-integrated advanced nozzle configuration

Takahashi

2017

JFST

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A conceptual study of a supersonic cruise aircraft employing an airframe-integrated linear aerospike propulsion system was conducted based on the evaluation of the thrust performance, propulsion efficiency, cruise performance, and flight attitude characteristics. The thrust performance was evaluated through physics-based performance prediction models established for linear aerospike nozzles by accounting for the freestream effect based on wind tunnel experiments. The airframe geometry was premised to be similar to that of the Concorde but was given only a minor alternation in the span geometry and on-design flight conditions. The airframe configuration, equipped with a boattail integrated upstream of the primary cell nozzle exit of the primary airbreathing engine, enabled the freestream effect to be utilized by increasing the surface pressure of the linear aerospike-type airframe aft-body, thus increasing the total thrust. The boattail configuration is beneficial as it prevents potential thrust loss that is anticipated for transonic flight conditions. The force balance analysis indicated that the proposed conceptual aircraft is feasible in terms of the aerodynamic center location. Results of the feasibility study showed that both the cruise performance and fuel consumption efficiency can be improved by employing the airframe-integrated aerospike propulsion system compared with those of some existing supersonic aircraft. Thus, the minor alternation in airframe design based on the existing supersonic aircraft offers significant improvement in performance and environmental concerns.

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Experiments on Shielding of Jet Noise by Airframe Surfaces

Cited by 29 publications

References 9 publications

Effects of Source Redistribution on Jet Noise Shielding

Effects of Source Redistribution on Jet Noise Shielding

Airframe Shielding of Noncompact Aviation Noise Sources: Theory and Experiment

Conceptual study of supersonic transports employing airframe-integrated advanced nozzle configuration

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