Effect of Uniform Chevrons on Cruise Shockcell Noise

Bultemeier, Eric; Ganz, Ulrich; Premo, John; Nesbitt, Eric

doi:10.2514/6.2006-2440

Cited by 15 publications

(7 citation statements)

References 4 publications

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“…Several fan nozzles are tested on engine 3 in an attempt to reduce shock-associated noise in cruise flight. Mengle et al [21,23] and Bultemeier et al [22] have shown recently that fan chevrons may reduce shock noise in cruise by up to 5 dB in the low frequencies on the external fuselage skin. They have also shown a sensitivity of reduction efficiency on the fan chevron design and the engine operating conditions.…”

Section: Low-noise Fan Nozzles 331 Acoustic Resultsmentioning

confidence: 99%

“…Besides, the use of chevrons to reduce the BBSAN component in high-bypass-ratio jets is reported in several studies [19,20]. The noise reduction potential of different chevron concepts on fan and core nozzles has also been qualified in flight tests in cruise conditions [21,22,23]. The mechanisms by which chevrons affect BBSAN has not been fully clarified.…”

Section: Introductionmentioning

confidence: 99%

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Understanding and Reduction of Cruise Jet Noise at Aircraft Level

Huber

Bulté

Laurendeau³

et al. 2014

International Journal of Aeroacoustics

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Within the LINFaN research project, Airbus and Rolls-Royce have jointly investigated the acoustic impact of supersonic jet noise on the fuselage of an Airbus A340 equipped with Rolls-Royce Trent 500 engines in cruise conditions. The main results are presented in this paper. The influence of chevron fan nozzles designed to reduce cruise jet noise on the rear fuselage is investigated. The characterization of both the acoustic field and the aerodynamic flow is carried out. The acoustic data are obtained from a microphone array on the rear fuselage. After specific data de-noising, the acoustic spectra radiated on the fuselage by only the right inner engine are estimated. Beamforming acoustic maps are also computed to localize the jet noise sources. Besides, the supersonic jet flows are characterized by RANS CFD approach. For the baseline round nozzle, the acoustic results show the presence of two distinct broadband shock-associated noise contributions on the fuselage. The first pattern is observed in the far aft section of the fuselage for Strouhal numbers based on the jet mixing diameter and velocity between St = 4 and 6. The other pattern, around St = 1, radiates preferably forward. In addition, the high frequency source is located between 4 and 5 mixed jet diameters past the secondary nozzle exhaust plane, while the low frequency source is located farther downstream between 7 and 8 mixed jet diameters. Shock-associated noise is usually associated with the interaction between shock cells and turbulent shear-layers. We postulate that the high-frequency noise component results from the interaction between the shock-cells in the secondary flow and the inner shear-layer, while the low-frequency component is due to the interaction between shock cells and the outer shear-layer. This interpretation is consistent with two observations. The first observation is a strong modification of the measured high frequency noise when the engine is pushed to high power. At

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Section: Low-noise Fan Nozzles 331 Acoustic Resultsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Understanding and Reduction of Cruise Jet Noise at Aircraft Level

Huber

Bulté

Laurendeau³

et al. 2014

International Journal of Aeroacoustics

View full text Add to dashboard Cite

show abstract

“…Data are only shown for observation angles and chevron configurations where BBSN is a dominant feature in the acoustic spectra (and, therefore, are not shown for the P12L15W20 chevron at M fe ¼1.23). Low-penetration chevrons 23 where baseline BBSN levels are only slightly above those of the broadband noise and all high-penetration chevrons increase high-frequency broadband noise in frequency ranges near those for those of BBSN. All highpenetration chevrons reduce peak BBSN levels for small inlet angles (less than 851).…”

Section: Acousticsmentioning

confidence: 95%

“…8 and 9 indicate that a reasonable approximation of chevron-acoustic performance for overexpanded jets operated with simulated flight streams can be made through experiments made with static flight conditions. Previous investigations with subsonic jets showed forward flight had a significant impact on chevron-noise-reduction characteristics [23].…”

Section: Acousticsmentioning

confidence: 99%

“…Studies have shown the addition of chevrons decreases shock-cell spacing [20,21] (and, therefore, increases the peak shock-noise frequency) and impacts shock-cell strength as a result of short wavelength waves (compression and expansion) generated at the chevron trailing edges interacting with the shock-cell structure produced by the jet underexpansion [22]. Alterations of the shock cells can lead to reduced shock-associated noise [23,24] although reports of increased shock associated noise are also found in the literature [25]. High-penetration chevrons have been shown to produce greater BBSN reduction than streamlined chevrons [26].…”

Section: Introductionmentioning

confidence: 97%

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