Hostname: page-component-586b7cd67f-rcrh6 Total loading time: 0 Render date: 2024-11-24T11:40:00.288Z Has data issue: false hasContentIssue false
  • English
  • Français

Aerofoil broadband noise reductions through double-wavelength leading-edge serrations: a new control concept

Published online by Cambridge University Press:  14 September 2018

P. Chaitanya Open the ORCID record for P. Chaitanya [Opens in a new window] ,
P. Joseph ,
S. Narayanan  and
J. W. Kim Open the ORCID record for J. W. Kim [Opens in a new window]
P. Chaitanya*
Affiliation:
University of Southampton, Southampton SO17 1BJ, UK
P. Joseph
Affiliation:
University of Southampton, Southampton SO17 1BJ, UK
S. Narayanan
Affiliation:
University of Southampton, Southampton SO17 1BJ, UK
J. W. Kim
Affiliation:
University of Southampton, Southampton SO17 1BJ, UK
*
†Email address for correspondence: [email protected]
Get access Rights & Permissions [Opens in a new window]

Abstract

Aerofoils operating in a turbulent flow generate broadband noise by scattering vorticity into sound at the leading edge. Previous work has demonstrated the effectiveness by which serrations, or undulations, introduced onto the leading edge, can substantially reduce broadband leading-edge noise. All of this work has focused on sinusoidal (single-wavelength) leading-edge serration profiles. In this paper, a new leading-edge serration geometry is proposed which provides significantly greater noise reductions compared to the maximum noise reductions achievable by single-wavelength serrations of the same amplitude. This is achieved through destructive interference between different parts of the aerofoil leading edge, and therefore involves a fundamentally different noise reduction mechanism from conventional single-wavelength serrations. The new leading-edge serration profiles simply comprise the superposition of two single-wavelength components of different wavelength, amplitude and phase with the objective of forming two roots that are sufficiently close together and separated in the streamwise direction. Compact sources located at these root locations then interfere, leading to less efficient radiation than single-wavelength geometries. A detailed parametric study is performed experimentally to investigate the sensitivity of the noise reductions to the profile geometry. A simple model is proposed to explain the noise reduction mechanism for these double-wavelength serration profiles and shown to be in close agreement with the measured noise reduction spectra. The study is primarily performed on flat plates in an idealized turbulent flow. The paper concludes by introducing the double-wavelength serration on a 10 % thick aerofoil, where near-identical noise reductions are obtained compared to the flat plate.

JFM classification

Acoustics: Acoustics Acoustics: Aeroacoustics Acoustics: Noise control
Type
JFM Papers
Information
Journal of Fluid Mechanics , Volume 855 , 25 November 2018 , pp. 131 - 151
Check for updates
Copyright
© 2018 Cambridge University Press 

Access options

Get access to the full version of this content by using one of the access options below. (Log in options will check for institutional or personal access. Content may require purchase if you do not have access.)

Footnotes

‡

Present address: IIT(ISM), Dhanbad, Jharkhand, India 826004

References

Amiet, R. K. 1975 Acoustic radiation from an airfoil in a turbulent stream. J. Sound Vib. 41 (4), 407–420.Google Scholar
Ayton, L. & Chaitanya, P. 2018 Analytic solutions for reduced leading-edge noise aerofoils. In 24th AIAA/CEAS Aeroacoustics Conference. AIAA Paper 2018–3284.Google Scholar
Cannard, M., Joseph, P., Chaitanya, P. & Kim, J.-W. 2018 Numerical investigation into slitted leading-edge profiles for reducing interaction noise. In International Congress on Sound and Vibration.Google Scholar
Chaitanya, P. & Joseph, P. 2018 Slitted leading edge profiles for the reduction of turbulence–aerofoil interaction noise. J. Acoust. Soc. Am. 143 (6), 3494–3504.Google Scholar
Chaitanya, P., Joseph, P. & Ayton, L. 2018 On the superior performance of leading edge slits over serrations for the reduction of aerofoil interaction noise. In 24th AIAA/CEAS Aeroacoustics Conference. AIAA Paper 2018–3121.Google Scholar
Chaitanya, P., Joseph, P., Narayanan, S., Vanderwel, C., Turner, J., Kim, J. W. & Ganapathisubramani, B. 2017 Performance and mechanism of sinusoidal leading edge serrations for the reduction of turbulence–aerofoil interaction noise. J. Fluid Mech. 818, 435–464.Google Scholar
Chaitanya, P., Narayanan, S., Joseph, P. & Kim, J. W.2016 Leading edge serration geometries for significantly enhanced leading edge noise reductions. In 22nd AIAA/CEAS Aeroacoustics Conference. AIAA Paper 2016-2736.Google Scholar
Chong, T. P., Joseph, P. F. & Davies, P. O. A. L. 2008 A parametric study of passive flow control for a short, high area ratio 90° curved diffuser. J. Fluids Engng 130 (11), 111104.Google Scholar
Chong, T. P., Vathylakis, A., McEwen, A., Kemsley, F., Muhammad, C. & Siddiqi, S. 2015 Aeroacoustic and aerodynamics performance of an aerofoil subjected to sinusoidal leading edges. In 21st AIAA/CEAS Aeroacoustics Conference.Google Scholar
Clair, V., Polacsek, C., Garrec, T. L., Reboul, G., Gruber, M. & Joseph, P. 2013 Experimental and numerical investigation of turbulence–airfoil noise reduction using wavy edges. AIAA J. 51 (11), 2695–2713.Google Scholar
Gea-Aguilera, F., Gill, J. R., Angland, D. & Zhang, X. 2017 Wavy leading edge airfoils interacting with anisotropic turbulence. In 23rd AIAA/CEAS Aeroacoustics Conference. AIAA Paper 2017-3370.Google Scholar
Hersh, A. S., Soderman, P. T. & Hayden, R. E. 1974 Investigation of acoustic effets of leading edge serrations on airfoils. J. Aircraft 11 (4), 197–202.Google Scholar
Hinze, J. O. 1975 Turbulence, 2nd edn. McGraw-Hill.Google Scholar
Kim, J. W., Haeri, S. & Joseph, P. F. 2016 On the reduction of aerofoil–turbulence interaction noise associated with wavy leading edges. J. Fluid Mech. 792, 526–552.Google Scholar
Lau, A. S. H., Haeri, S. & Kim, J. W. 2013 The effect of wavy leading edges on aerofoil–gust interaction noise. J. Sound Vib. 332, 6234–6253.Google Scholar
Lyu, B. & Azarpeyvand, M. 2017 On the noise prediction for serrated leading edges. J. Fluid Mech. 826, 205–234.Google Scholar
Mish, P. F.2003 An experimental investigation of unsteady surface pressure on single and multiple airfoils. PhD thesis, Virginia Polytechnic Institute and State University.Google Scholar
Moreau, S. & Roger, M. 2007 Competing broadband noise mechanisms in low speed axial fans. AIAA J. 45 (1), 48–57.Google Scholar
Narayanan, S., Chaitanya, P., Haeri, S., Joseph, P., Kim, J. W. & Polacsek, C. 2015 Airfoil noise reductions through leading edge serrations. Phys. Fluids 27 (2), 025109.Google Scholar
Roach, P. E. 1987 The generation of nearly isotropic turbulence by means of grids. Heat Fluid Flow 8 (2), 82–92.Google Scholar
Roger, M. & Moreau, S. 2010 Extensions and limitations of analytical airfoil broadband noise models. Intl J. Aeroacoust. 9 (3), 273–305.Google Scholar
Roger, M., Schram, C., Santana, C. & De, L. 2013 Reduction of airfoil turbulence–impingement noise by means of leading-edge serrations and/or porous materials. In AIAA/CEAS Aeroacoustics Conference, Berlin, Germany.Google Scholar
Sanjose, M., Jaiswal, P., Arroyo, C. P., Moreau, S., Towne, A., Lele, S. K. & Mann, A. 2017 Laminar boundary layer instability noise. In 23rd AIAA/CEAS Aeroacoustics Conference.Google Scholar
Turner, J., Kim, J. W., Chaitanya, P. & Joseph, P.2016 Towards understanding aerofoils with dual-frequency wavy leading edges interacting with vortical disturbances. In 22nd AIAA/CEAS Aeroacoustics Conference. AIAA Paper 2016-2951.Google Scholar
Turner, J. M. & Kim, J. W. 2017 Aeroacoustic source mechanisms of a wavy leading edge undergoing vortical disturbances. J. Fluid Mech. 811, 582–611.Google Scholar