Effect of trailing edge serration-flow misalignment on airfoil noise emissions

León, Carlos Arce; Martinez, R. Merino; Ragni, Daniele; Avallone, Francesco; Scarano, Fulvio; Pröbsting, Stefan; Snellen, Mirjam; Simons, Dick G.; Madsen, Jesper

doi:10.1016/j.jsv.2017.05.035

Cited by 62 publications

(43 citation statements)

References 35 publications

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“…The beamforming results were normalized by the integrated array response for a point source in the center of the integration area, also known as Point Spread Function (PSF). This way, more physical results are obtained, not conditioned by the assumption that only point sources are present [24,[29][30][31][32].…”

Section: Iiia Methods For the Wind-tunnel Experimentsmentioning

confidence: 99%

Comparing flyover noise measurements to full-scale nose landing gear wind tunnel experiments for regional aircraft

Martinez

Neri

Snellen

et al. 2017

23rd AIAA/CEAS Aeroacoustics Conference

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The noise emissions of the nose landing gear of a full-scale model tested in a wind tunnel, and of three regional aircraft types in flyover measurements are compared in this contribution. The geometries of the nose landing gears in all cases were similar. Microphone arrays and beamforming algorithms were used to determine the sound emissions of the nose landing gears. A good agreement was found between the overall trends of the frequency spectra in all cases. Moreover, the expected 6 th power law with the flow velocity was confirmed for both experiments. On the other hand, strong tonal peaks (at around 2200 Hz) were only found for the flyover tests. As the frequencies of the tones do not depend on the aircraft velocity, they are thought to be caused by cavities found in structural components of the nose landing gear. Removing these tones would cause overall noise reductions up to 2 dB in the frequency range examined. It is, therefore, recommended to further investigate this phenomenon, to include cavity-noise estimations in the current noise prediction models, and to eliminate such cavities where possible.

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Section: Iiia Methods For the Wind-tunnel Experimentsmentioning

confidence: 99%

Comparing flyover noise measurements to full-scale nose landing gear wind tunnel experiments for regional aircraft

Martinez

Neri

Snellen

et al. 2017

23rd AIAA/CEAS Aeroacoustics Conference

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“…Another common technique that is used is trailing edge serrations. This has been extensively researched and have shown positive aeroacoustic results in both the laminar boundary layer case (Chong et al, 2010) and turbulent boundary layer case (Arce León et al, 2017).…”

Section: Introductionmentioning

confidence: 99%

An aeroacoustic investigation into the effect of self-oscillating trailing edge flaplets

Talboys

Geyer

Brücker

2019

Journal of Fluids and Structures

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The aeroacoustics of a NACA 0012 aerofoil with an array of self-oscillating flexible flaplets attached on the trailing edge has been investigated at low to moderate chord based Reynolds number (50,000 -350,000) and at geometric angles of attack from α g = 0 • -20 • . When the aerofoil is untripped, tonal peaks are observed on the baseline aerofoil. When the passive flaplets are attached to the pressure side of the aerofoil, the tonal peak is removed. If the flaplets are then placed on the suction side, the tonal peak is reduced, but not removed. It is therefore hypothesised that the flaplets on the pressure side modifies the laminar separation bubble situated on the pressure side of the aerofoil, a key mechanism for tonal noise. Throughout all cases, both tripped and untripped, a low frequency (0.1 kHz -0.6 kHz) noise reduction and a slight increase at higher frequencies (>2 kHz) is seen. This gives an average overall sound pressure level (OSPL) reduction of 1.5 -2 dB for the flaplets affixed to the pressure side. The cases where the tonal noise component is removed an OSPL reduction of up to 20 dB can be seen.

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“…Strong streamwise vortical structures have been observed originating from the serration edges, and increased turbulence activity has been measured at the pressure side near them [4]. The turbulent structures near the edges are therefore significantly modified and are vastly different on the upper and lower serration sides.…”

Section: Discussionmentioning

confidence: 99%

“…In [15], for example, single microphones were used to characterize the noise directivity. A wide frequency range was presented, from around 20 to 20 × 10 4 Hz, while the range where noise reduction was observed was found to be case dependent, typically ranging from around 200 Hz to a Strouhal number-dependent upper limit [15].…”

Section: Introductionmentioning

confidence: 99%

Acoustic Emissions of Semi-Permeable Trailing Edge Serrations

et al. 2017

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The trailing edge of a NACA 0018 airfoil is modified through the attachment of serrations with different degrees of permeability. Acoustic beamforming is used to inspect the turbulent boundary layer-trailing edge noise emissions from the unmodified and serrated trailing edges. Different freestream velocities and angles of attack are investigated. The serration permeability is prescribed by having slits cut into the solid surface of the serrations in two different configurations. The results indicate that a certain benefit in noise reduction is obtained from a mixed solid/slitted configuration, while a fully slitted configuration loses most of the noise reduction performance.

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Effect of trailing edge serration-flow misalignment on airfoil noise emissions

Cited by 62 publications

References 35 publications

Comparing flyover noise measurements to full-scale nose landing gear wind tunnel experiments for regional aircraft

Comparing flyover noise measurements to full-scale nose landing gear wind tunnel experiments for regional aircraft

An aeroacoustic investigation into the effect of self-oscillating trailing edge flaplets

Acoustic Emissions of Semi-Permeable Trailing Edge Serrations

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