Novel Three-Dimensional Surface Treatments for Trailing-Edge Noise Reduction

There is an increased emphasis on reducing airframe noise in the last decades. Airframe noise is sound generated by the interaction of a turbulent flow with the aircraft geometry, and significantly contributes to the overall noise production during the landing phase. One examples of airframe noise is the noise generated at a wing's trailing edge, i.e., trailing-edge noise. In this contribution, we numerically explore the local application of riblets for the purpose of trailing-edge noise reduction. Two configurations are studied: i) a clean NACA0012 wing section as a reference, and ii) the same configuration with riblets installed at the wing's aft part. The numerical investigation follows a hybrid computational aeroacoustics approach, where the time-average flow is studied by means of RANS. Noise sources are generated by means of a stochastic approach called Fast Random Particle Mesh method. The results show a deceleration of the flow behind the riblets. Furthermore, the turbulent kinetic energy indicates increased unsteadiness behind the riblets which is shifted away from the wall due to the presence of the riblets. Lastly, the sound sources are investigated by means of the 3D Lamb-vector, which indicates a slight reduction in magnitude near the trailing edge.

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Concave serrations on broadband trailing edge noise reduction

23rd AIAA/CEAS Aeroacoustics Conference ◽

10.2514/6.2017-4174 ◽

2017 ◽

Cited By ~ 2

Author(s):

Daniele Ragni ◽

Francesco Avallone ◽

Wouter C. van der Velden

Keyword(s):

Noise Reduction ◽

Trailing Edge ◽

Trailing Edge Noise

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Benefits of curved serrations on broadband trailing-edge noise reduction

Journal of Sound and Vibration ◽

10.1016/j.jsv.2017.04.007 ◽

2017 ◽

Vol 400 ◽

pp. 167-177 ◽

Cited By ~ 32

Author(s):

F. Avallone ◽

W.C.P. van der Velden ◽

D. Ragni

Keyword(s):

Noise Reduction ◽

Trailing Edge ◽

Trailing Edge Noise

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An experimental investigation of trailing-edge noise reduction due to elasticity

2018 AIAA/CEAS Aeroacoustics Conference ◽

10.2514/6.2018-2802 ◽

2018 ◽

Author(s):

Maurício M. Nilton ◽

Yasir A. Malik ◽

André V. Cavalieri ◽

Leandro D. de Santana ◽

Mauricio V. Donadon ◽

...

Keyword(s):

Experimental Investigation ◽

Noise Reduction ◽

Trailing Edge ◽

Trailing Edge Noise

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Airfoil Trailing Edge Noise Reduction Using a Boundary-Layer Bump

Acta Acustica united with Acustica ◽

10.3813/aaa.919362 ◽

2019 ◽

Vol 105 (5) ◽

pp. 814-826 ◽

Cited By ~ 6

Author(s):

Yuejun Shi ◽

Seongkyu Lee

Keyword(s):

Boundary Layer ◽

Noise Reduction ◽

Suction Side ◽

Reynolds Numbers ◽

Numerical Approach ◽

Trailing Edge ◽

Velocity Deficit ◽

Trailing Edge Noise ◽

Field Noise ◽

High Reynolds

This paper presents a new idea of reducing airfoil trailing edge noise using a small bump in the turbulent boundary layer. First, we develop and validate a new computational approach to predict airfoil trailing edge noise using steady RANS CFD, an empirical wall pressure spectrum model, and Howe's diff raction theory. This numerical approach enables fast and accurate predictions of trailing edge noise, which is used to study the noise reduction from the bump for various airfoil geometries and flow conditions at high Reynolds numbers. Three types of bumps, the suction-side bump, pressure-side bump, and both-side bumps, are studied. The results show that all types of bumps are able to reduce far-field noise up to 10 dB compared to clean airfoils, but their impacts are diff erent in terms of the eff ective frequency range. Also, bumps with four diff erent heights are compared with each other to investigate the eff ect of the height of bumps on noise reduction. It is demonstrated that a bump causes velocity deficit within the boundary layer near the wall. This velocity deficit results in reduced turbulence kinetic energy near the wall, which is responsible for trailing edge noise reduction. Overall, this paper demonstrates the potential of a boundary-layer bump in trailing edge noise reduction and sheds light on the physical mechanism of noise reduction with boundary-layer bumps.

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Uniform flow injection into a turbulent boundary layer for trailing edge noise reduction

Physics of Fluids ◽

10.1063/5.0013461 ◽

2020 ◽

Vol 32 (8) ◽

pp. 085104 ◽

Cited By ~ 2

Author(s):

Máté Szőke ◽

Daniele Fiscaletti ◽

Mahdi Azarpeyvand

Keyword(s):

Boundary Layer ◽

Turbulent Boundary Layer ◽

Noise Reduction ◽

Flow Injection ◽

Uniform Flow ◽

Trailing Edge ◽

Trailing Edge Noise

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Features of owl wings that promote silent flight

Interface Focus ◽

10.1098/rsfs.2016.0078 ◽

2017 ◽

Vol 7 (1) ◽

pp. 20160078 ◽

Cited By ~ 28

Author(s):

Hermann Wagner ◽

Matthias Weger ◽

Michael Klaas ◽

Wolfgang Schröder

Keyword(s):

Noise Reduction ◽

Leading Edge ◽

Aerodynamic Performance ◽

Wing Loading ◽

Trailing Edge ◽

Future Directions ◽

Trailing Edge Noise ◽

Aerodynamic Properties ◽

Morphological Adaptations ◽

Noise Production

Owls are an order of birds of prey that are known for the development of a silent flight. We review here the morphological adaptations of owls leading to silent flight and discuss also aerodynamic properties of owl wings. We start with early observations (until 2005), and then turn to recent advances. The large wings of these birds, resulting in low wing loading and a low aspect ratio, contribute to noise reduction by allowing slow flight. The serrations on the leading edge of the wing and the velvet-like surface have an effect on noise reduction and also lead to an improvement of aerodynamic performance. The fringes at the inner feather vanes reduce noise by gliding into the grooves at the lower wing surface that are formed by barb shafts. The fringed trailing edge of the wing has been shown to reduce trailing edge noise. These adaptations to silent flight have been an inspiration for biologists and engineers for the development of devices with reduced noise production. Today several biomimetic applications such as a serrated pantograph or a fringed ventilator are available. Finally, we discuss unresolved questions and possible future directions.

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