Flight Test Investigation of Add-On Treatments to Reduce Aircraft Airframe Noise

Piet, Jean Francois; Davy, Renaud; Elias, G.; Siller, H.; Chow, L.C.; Seror, Christelle; Laporte, Florent

doi:10.2514/6.2005-3007

Cited by 36 publications

(15 citation statements)

References 2 publications

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“…Several studies about noise reduction effects by such large streamlined aerodynamic fairings around bogie have been conducted by wind tunnel test and flight test [14][15][16][17][18][19][20][21][22][23][24][25] . Several studies have also evaluated fairings using elastic membrane 17 , porous surface 19,21,22 , and slotted surface 21 for the noise reduction effect, instead of fairings using solid surface.…”

Section: Introductionmentioning

confidence: 99%

Numerical Simulation of a Two-Wheel Main Landing Gear with Low-Noise Fairings around Tire-Axle Region

Murayama

Yokokawa

Yamamoto

et al. 2012

18th AIAA/CEAS Aeroacoustics Conference (33rd AIAA Aeroacoustics Conference)

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The purpose of this paper is computational investigation of flowfield and noise reduction mechanism with low noise fairings for noise from tire-axle region of a two-wheel main landing gear. In this study, two types of fairing concepts around the bogie using solid surface and porous surface are investigated. The noise reduction effects and the directivity characteristics are shown by far-field noise measurements in the wind tunnel and numerical simulations. The changes of flow structure by two types of fairings around the bogie are clarified by steady-state and unsteady CFD computations. By the computations, it is clarified where to modify the geometries to improve both types of fairings. Through the computations, the design knowledge to search for noise reduction techniques and low noise design around tire-axle region of two-wheel type landing gears is obtained. NomenclatureC P = pressure coefficient t = computational time step FW-H = Ffowcs Williams and Hawkings K mp = 1.126 for kneeling gear; = 1.0 otherwise L Aircraft = representative length of aircraft L m = extended length of main landing gear [in] L Model = representative length of wind tunnel testing model N l = ultimate landing load factor N mss = number of main gear shock struts N mw = number of main wheels OASPL = overall sound pressure level R Aircraft = distance to evaluation location of far field noise at aircraft-scale R Model = distance to evaluation location of far field noise at model-scale Re = Reynolds number RTRI = Large-Scale Anechoic Wind Tunnel in Railway Technical Research Institute SPL = sound pressure level T = free-stream temperature U inf = free-stream velocity U Aircraft = aircraft speed U Model = free-stream velocity of wind tunnel test VR = variable resolution V stall = stall speed W l = landing design gross weight [lb]

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Section: Introductionmentioning

confidence: 99%

Numerical Simulation of a Two-Wheel Main Landing Gear with Low-Noise Fairings around Tire-Axle Region

Murayama

Yokokawa

Yamamoto

et al. 2012

18th AIAA/CEAS Aeroacoustics Conference (33rd AIAA Aeroacoustics Conference)

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“…As an alternative approach to wind-tunnel testing, a direct measure of landing-gear noise, and indeed the assessment of applied lownoise treatments [11], has been attempted by source localization techniques and flyover measurements using microphone arrays [12].…”

Section: Introductionmentioning

confidence: 99%

“…In addition, given the distance from the arrays to the landing gear, the low spatial resolution does not allow for analysis on a component basis nor does the aperture allow for low-frequency analysis. Challenges also arise from different and louder noise sources overlapping the frequency range of interest, although tests have been performed with aircraft engines operating at minimum idle reduced thrust (N1 20%) [11] to increase the signal-to-noise ratio.…”

Section: Introductionmentioning

confidence: 99%

Noise Characterization of a Full-Scale Nose Landing Gear

Bennett

Neri

Kennedy

2018

Journal of Aircraft

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This paper presents experimental results from a nose landing-gear test campaign. A highly detailed model of the nose section of a 90-seat configuration green regional aircraft concept was built and tested in an aeroacoustic open-jet wind tunnel at full scale. All of the landing-gear components, fixtures, and small details and associated structures such as the complete wheel bay, bay doors, and hydraulic dressings were included at full scale. This paper focuses on one element of the testing: that of component noise assessment. The dressings, wheels, torque link, steering pinion, bay doors, and then the main strut and drag stay were removed in succession, and an acoustic evaluation was performed at a range of velocities from M 0.12 to M 0.19. In addition, hub caps were installed on the wheels, and their performance as a low-noise treatment is presented and assessed for efficacy. The landing gear, doors, and bay generated most noise in the frequency range between 120 and 400 Hz, but appreciable noise above the baseline was measured up to 10 kHz. The low-to midfrequency aerodynamic noise was found to scale with V 6 , as usual; however, the spectra at high frequencies collapsed perfectly when scaled to V 7 , confirming the fact that high-frequency noise is radiated from the turbulent flow surrounding small features. The total noise output of the landing-gear assembly differs from that of the sum of the components in isolation due to installation effects. The research in this paper studied these effects and the influence of the components on each other.

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“…Bleeding air through the fairing results in a redistribution of the air flow. Flight tests using perforated fairings have been conducted before and demonstrated a noise decrease [4,5]. The aim of the present research is to investigate and optimize the noise reduction potential by perforating these fairings.…”

Section: Introductionmentioning

confidence: 99%

Landing gear noise control using perforated fairings

2009

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Landing gears of commercial aircraft make an important contribution to total aircraft noise in the approach configuration. Using fairings to shield components from high speed impingement reduces noise. Furthermore, perforating these fairings has been confirmed by flight tests to further enable noise reduction. Following an earlier fundamental study of the application of perforated fairings, a study has been performed to investigate and optimize the benefits of bleeding air through landing gear fairings. By means of wind tunnel tests, an aerodynamic and acoustic survey has been performed on a simplified generic main landing gear to explore the influence of (perforated) fairings on the lower part of the gear. The results show that for this specific case, the application of impermeable fairings reduces noise in the mid-and high frequency range by shielding sharp edged components from high velocity impingement. However, below 1 kHz the noise is shown to increase significantly. Application of the perforations is shown to diminish this low frequency increase whilst maintaining the reduction in the mid-and high frequency range. The aerodynamic and acoustic measurements point in the direction of the separated flow of the fairings interacting with the downstream gear components responsible for the low frequency noise increase. Bleeding of the air through the fairings reduces the large scale turbulence in the proximity of these components and hence diminishes the low frequency noise increase.

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Flight Test Investigation of Add-On Treatments to Reduce Aircraft Airframe Noise

Cited by 36 publications

References 2 publications

Numerical Simulation of a Two-Wheel Main Landing Gear with Low-Noise Fairings around Tire-Axle Region

Numerical Simulation of a Two-Wheel Main Landing Gear with Low-Noise Fairings around Tire-Axle Region

Noise Characterization of a Full-Scale Nose Landing Gear

Landing gear noise control using perforated fairings

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