Bluff Body Noise Control Using Perforated Fairings

Boorsma, K.; Zhang, Xin; Molin, Nicolas; Chow, L.C.

doi:10.2514/1.32766

Cited by 50 publications

(24 citation statements)

References 8 publications

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“…It reveals the sides of the lower articulation link fairing being responsible for the perforate noise peak just above f = 10 kHz. This is conform to results in previous literature [8,9], which already showed the shearing flow past the perforate is the cause of most of the noise. A non-dimensional frequency referenced to local velocity and orifice diameter d or can be defined using…”

Section: On-surface Microphonessupporting

confidence: 93%

“…It appears that the stagnation area perforations are responsible for most of the noise decrease, for both the articulation link and undertray fairing. Agreeing with previous experiments using a model geometry similar to the lower articulation link fairing [8,9], most of the perforate noise is emitted from the lower articulation link fairing sides at a Strouhal number of St = 0.33 based on the orifice diameter d or and the local flow velocity.…”

Section: Discussionsupporting

confidence: 70%

“…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. Armed with the lessons learnt from this experiment, aerodynamics and acoustics of a simplified landing gear model have been investigated.…”

Section: Introductionmentioning

confidence: 99%

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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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Section: On-surface Microphonessupporting

confidence: 93%

Section: Discussionsupporting

confidence: 70%

Section: Introductionmentioning

confidence: 99%

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Landing gear noise control using perforated fairings

2009

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“…Such tests are commonly used in studying the aerodynamic noise produced by aircraft landing gear, for example References [47][48][49]. King and Pfizenmaier [50] have performed wind tunnel tests on the noise radiated by cylinders with different cross-sections in studying the aerodynamic noise produced from pantographs.…”

Section: Full Scale Tests On Componentsmentioning

confidence: 99%

Recent developments in the prediction and control of aerodynamic noise from high-speed trains

Thompson

Iglesias

Liu

et al. 2015

International Journal of Rail Transportation

119

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At speeds above 300-350 km/h, the main source of noise from trains is the aerodynamic noise caused by the air flow over the train structure. The sound level increases with train speed at a rate of between 60 and 80 times the logarithm of the speed so that, as speeds increase further, the noise increases dramatically. The main aerodynamic noise is produced by the air flow passing over the pantograph, the train nose, the bogie region and cavities such as the pantograph recess and the inter-coach gap. Experimental and numerical methods for studying aerodynamic noise are reviewed including the use of microphone arrays, wind tunnels, computational fluid dynamics and semi-empirical methods. Potential mitigation measures that can control aerodynamic noise are also reviewed.

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“…al. [2] performed experimental study to investigate and optimize the effect of different perforated fairing on the noise control at different location. The fairing self-noise is reduced remarkably by breakdown of the vortex shedding process, resulting in a reduction of associated broadband noise level.…”

Section: Qwurgxfwlrqmentioning

confidence: 99%

Vortex shedding control of circular cylinder by perforated shroud in deep water

et al. 2017

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$EVWUDFW The aim of the present study is to control the vortex shedding downstream of a circular cylinder (inner cylinder) by the existence of outer perforated cylinder concentrically located around the inner cylinder in deep water. The flow characteristics downstream of concentrically placed coupled cylinders were investigated quantitatively by the Particle Image Velocimetry (PIV) technique. Diameter of the outer perforated cylinder and inner cylinder were kept constant as Do=100 mm and Di=50 mm. The depthaveraged free-stream velocity was also kept constant as U=100 mm/s which corresponded to the Reynolds number of ReDo=10,000 based on the outer cylinder diameter. Experiments were conducted for six porosities (β = 0.3, 0.4, 0.5, 0.6, 0.7 and 0.8) in order to show the effect of these parameters on the flow control. Maximum values of both Reynolds shear stress, and turbulence kinetic energy, significantly decreased with the existence of outer perforated cylinder and also, the location of peak magnitudes of turbulence statistics occurred at locations further downstream compared to the bare cylinder case. The most effective control was revealed for the porosity of β=0.7. ,QWURGXFWLRQIt is well-known phenomena that flow over a circular cylinder which causes acoustic noise, vibration, fatigue and shortens the life of cylinder. To end this, the flow control around a cylinder has been an attractive topic for more than a century due to its engineering significance and in part due to its tempting simplicity in setting up arrangements in experimental or numerical studies.Ikeda and Takaishi [1] showed that the stable wake shear layers of the perforated cylinder and suppression of Aeolian tone are achieved due to the jets emitted from the holes at regular intervals. Boorsma et. al. [2] performed experimental study to investigate and optimize the effect of different perforated fairing on the noise control at different location. The fairing self-noise is reduced remarkably by breakdown of the vortex shedding process, resulting in a reduction of associated broadband noise level. Zho and Cheng [3] demonstrated that lift reduction of circular cylinder can be achieved by properly choosing the porous material. Kleissl and Georgakis [4] performed experimental study in order to show the effect of modifying bridge cable shape and surface on suppression of the vortex induced vibration. They revealed that shroud cylinder significantly reduced the vortex-induced oscillating lift forces. Yu et al. [5] studied numerically on the steady flow around a porous circular cylinder. They found that contrary to that of the solid cylinder, the recirculating wake develops downstream of or within the porous cylinder, but not from the surface of it.Ozkan et al. [6] expressed that the change in flow characteristics downstream of circular cylinder surrounded by a permeable cylinder in shallow water using particle image velocimetry technique. They observed that the peak magnitude of turbulent kinetic energy and Reynolds stress decrease remark...

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Bluff Body Noise Control Using Perforated Fairings

Cited by 50 publications

References 8 publications

Landing gear noise control using perforated fairings

Landing gear noise control using perforated fairings

Recent developments in the prediction and control of aerodynamic noise from high-speed trains

Vortex shedding control of circular cylinder by perforated shroud in deep water

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