Control of Noise Sources on Aircraft Landing Gear Bogies

Smith, M. G.; Fenech, Benjamin; Chow, L.C.; Molin, Nicolas; Dobrzynski, W.; Seror, Christelle

doi:10.2514/6.2006-2626

Cited by 20 publications

(16 citation statements)

References 2 publications

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“…Two-phase piezoelectric composites, comprised of piezoelectric particles embedded within a continuous polymer matrix, have attracted much attention due to their flexibility and ease of processing, 1,2 and applications to dielectric, [3][4][5] sensing/actuating, [6][7][8][9] energy harvesting, 1,9,10 and acoustic damping [11][12][13] applications. However, these materials suffer from relatively small values of piezoelectric and dielectric properties due to the inherent insulative properties of the polymer matrix phase, [14][15][16][17][18] which is associated with difficulties in the polarization of these materials 19 and contact resistance at the particle/matrix interface.…”

Section: Introductionmentioning

confidence: 99%

Dielectric and piezoelectric properties of percolative three-phase piezoelectric polymer composites

Sundar¹

2016

Journal of Vacuum Science &Amp; Technology B, Nanotechnology and Microelectronics: Materials, Processing, Measurement, and Phen

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Articles you may be interested in Design, fabrication, and properties of 2-2 connectivity cement/polymer based piezoelectric composites with varied piezoelectric phase distribution J. Appl. Phys. 116, 244103 (2014) Three-phase piezoelectric bulk composites were fabricated using a mix and cast method. The composites were comprised of lead zirconate titanate (PZT), aluminum (Al), and an epoxy matrix. The volume fraction of the PZT and Al was varied from 0.1 to 0.3 and 0.0 to 0.17, respectively. The influences of an electrically conductive filler (Al), polarization process (contact and Corona), and Al surface treatment, on piezoelectric and dielectric properties, were observed. The piezoelectric strain coefficient, d 33 , effective dielectric constant, e r , capacitance, C, and resistivity were measured and compared according to polarization process, the volume fraction of constituent phases, and Al surface treatment. The maximum values of d 33 were $3.475 and $1.0 pC/N for corona and contact poled samples, respectively, for samples with volume fractions of 0.40 and 0.13 of PZT and Al (surface treated), respectively. Also, the maximum dielectric constant for the surface treated Al samples was $411 for volume fractions of 0.40 and 0.13 for PZT and Al, respectively. The percolation threshold was observed to occur at an aluminum volume fraction of 0.13. The composites achieved a percolated state for Al volume fractions >0.13 for both contact and corona poled samples. In addition, a comparative time study was conducted to examine the influence of surface treatment processing time of aluminum particles. The effectiveness of the surface treatment, sample morphology and composition was observed with the aid of scanning electron microscope and energy dispersive x-ray spectroscopy images. These images were correlated with piezoelectric and dielectric properties.

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Section: Introductionmentioning

confidence: 99%

Dielectric and piezoelectric properties of percolative three-phase piezoelectric polymer composites

Sundar¹

2016

Journal of Vacuum Science &Amp; Technology B, Nanotechnology and Microelectronics: Materials, Processing, Measurement, and Phen

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“…Recent research on the subject [6,7] has confirmed the flight test results, although the corresponding flow behavior has not been investigated thoroughly. An early study on perforated fairings employing a simplified bluff body geometry [8,9] suggests that breakdown of the large scale flow structures associated with the fairings can be a major benefit, although caution should be exercised to prevent the adverse effect of perforate self-noise.…”

Section: Introductionmentioning

confidence: 63%

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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“…Recent research on the subject 4,5 has confirmed the flight test results, although the corresponding flow behavior has not been investigated. A previous study on perforated fairings employing a simplified bluff body geometry 6 has shown that breakdown of the large scale flow structures associated with the fairings can be a major benefit, although one should be careful to prevent the adverse effect of perforate self-noise.…”

mentioning

confidence: 62%

Perforated Fairings for Landing Gear Noise Control

Boorsma

Zhang

Molin

2008

14th AIAA/CEAS Aeroacoustics Conference (29th AIAA Aeroacoustics Conference)

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I. AbstractLanding 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 a more fundamental study on 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 A340 look alike 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 increase. A sharp noise increase is present in the ground view direction at the 500 Hz centred tertsband for the solid fairing, which is confirmed to originate from the articulation link fairing. The flow around the wheels remains largely unaltered by application of the fairings. Furthermore the application of fairings is shown to suppress vortex shedding from the lower part of the main leg.A study on the effectiveness of perforation location reveals that the stagnation area perforations are responsible for most of the low frequency noise decrease. Both articulation link and undertray fairing contribute to the reduction. Exposing the perforate outside the stagnation area induces perforate self-noise, most significantly on the sides of the lower articulation link fairing. Agreeing with previous studies, the phenomenon scales with the local component of the shearing flow velocity and orifice diameter.

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Control of Noise Sources on Aircraft Landing Gear Bogies

Cited by 20 publications

References 2 publications

Dielectric and piezoelectric properties of percolative three-phase piezoelectric polymer composites

Dielectric and piezoelectric properties of percolative three-phase piezoelectric polymer composites

Landing gear noise control using perforated fairings

Perforated Fairings for Landing Gear Noise Control

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