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On the manipulation of flow and acoustic fields of a blunt trailing edge aerofoil by serrated leading edges.
J Acoust Soc Am. 2020 Jun; 147(6):3932.JA

Abstract

This paper employs serrated leading edges to inject streamwise vorticity to the downstream boundary layer and wake to manipulate the flow field and noise sources near the blunt trailing edge of an asymmetric aerofoil. The use of a large serration amplitude is found to be effective to suppress the first noise source-bluntness-induced vortex shedding tonal noise-through the destruction of the coherent eigenmodes in the wake. The second noise source is the instability noise, which is produced by the interaction between the boundary layer instability and separation bubble near the blunt edge. The main criterion needed to suppress this noise source is related to a small serration wavelength because, through the generation of more streamwise vortices, it would facilitate a greater level of destructive interaction with the separation bubble. If the leading edge has both a large serration amplitude and wavelength, the interaction between the counter-rotating vortices themselves would trigger a turbulent shear layer through an inviscid mechanism. The turbulent shear layer will produce strong hydrodynamic pressure fluctuations to the trailing edge, which then scatter into broadband noise and transform into a trailing edge noise mechanism. This would become the third noise source that can be identified in several serrated leading edge configurations. Overall, a leading edge with a large serration amplitude and small serration wavelength appears to be the optimum choice to suppress the first and second noise sources and, at the same time, avoid the generation of the third noise source.

Authors+Show Affiliations

Department of Mechanical and Aerospace Engineering, Brunel University London, Uxbridge, UB8 3PH, United Kingdom.Department of Mechanical and Aerospace Engineering, Brunel University London, Uxbridge, UB8 3PH, United Kingdom.Institute of Sound and Vibration Research, University of Southampton, Southampton, SO17 1BJ, United Kingdom.Institute of Sound and Vibration Research, University of Southampton, Southampton, SO17 1BJ, United Kingdom.Fluids and Thermal Engineering Group, University of Nottingham, Nottingham, NG7 2RD, United Kingdom.Fluids and Thermal Engineering Group, University of Nottingham, Nottingham, NG7 2RD, United Kingdom.School of Mathematics, Computer Science and Engineering, City University London, London, EC1V 0HB, United Kingdom.School of Mathematics, Computer Science and Engineering, City University London, London, EC1V 0HB, United Kingdom.Faculty of Aerospace Engineering, Technion Israel Institute of Technology, Israel.

Pub Type(s)

Journal Article

Language

eng

PubMed ID

32611165

Citation

Hasheminejad, Seyed Mohammad, et al. "On the Manipulation of Flow and Acoustic Fields of a Blunt Trailing Edge Aerofoil By Serrated Leading Edges." The Journal of the Acoustical Society of America, vol. 147, no. 6, 2020, p. 3932.
Hasheminejad SM, Chong TP, Lacagnina G, et al. On the manipulation of flow and acoustic fields of a blunt trailing edge aerofoil by serrated leading edges. J Acoust Soc Am. 2020;147(6):3932.
Hasheminejad, S. M., Chong, T. P., Lacagnina, G., Joseph, P., Kim, J. H., Choi, K. S., Omidyeganeh, M., Pinelli, A., & Stalnov, O. (2020). On the manipulation of flow and acoustic fields of a blunt trailing edge aerofoil by serrated leading edges. The Journal of the Acoustical Society of America, 147(6), 3932. https://doi.org/10.1121/10.0001377
Hasheminejad SM, et al. On the Manipulation of Flow and Acoustic Fields of a Blunt Trailing Edge Aerofoil By Serrated Leading Edges. J Acoust Soc Am. 2020;147(6):3932. PubMed PMID: 32611165.
* Article titles in AMA citation format should be in sentence-case
TY - JOUR T1 - On the manipulation of flow and acoustic fields of a blunt trailing edge aerofoil by serrated leading edges. AU - Hasheminejad,Seyed Mohammad, AU - Chong,Tze Pei, AU - Lacagnina,Giovanni, AU - Joseph,Phillip, AU - Kim,Jung-Hoon, AU - Choi,Kwing-So, AU - Omidyeganeh,Mohammad, AU - Pinelli,Alfredo, AU - Stalnov,Oksana, PY - 2020/7/3/entrez SP - 3932 EP - 3932 JF - The Journal of the Acoustical Society of America JO - J. Acoust. Soc. Am. VL - 147 IS - 6 N2 - This paper employs serrated leading edges to inject streamwise vorticity to the downstream boundary layer and wake to manipulate the flow field and noise sources near the blunt trailing edge of an asymmetric aerofoil. The use of a large serration amplitude is found to be effective to suppress the first noise source-bluntness-induced vortex shedding tonal noise-through the destruction of the coherent eigenmodes in the wake. The second noise source is the instability noise, which is produced by the interaction between the boundary layer instability and separation bubble near the blunt edge. The main criterion needed to suppress this noise source is related to a small serration wavelength because, through the generation of more streamwise vortices, it would facilitate a greater level of destructive interaction with the separation bubble. If the leading edge has both a large serration amplitude and wavelength, the interaction between the counter-rotating vortices themselves would trigger a turbulent shear layer through an inviscid mechanism. The turbulent shear layer will produce strong hydrodynamic pressure fluctuations to the trailing edge, which then scatter into broadband noise and transform into a trailing edge noise mechanism. This would become the third noise source that can be identified in several serrated leading edge configurations. Overall, a leading edge with a large serration amplitude and small serration wavelength appears to be the optimum choice to suppress the first and second noise sources and, at the same time, avoid the generation of the third noise source. SN - 1520-8524 UR - https://www.unboundmedicine.com/medline/citation/32611165/On_the_manipulation_of_flow_and_acoustic_fields_of_a_blunt_trailing_edge_aerofoil_by_serrated_leading_edges L2 - https://doi.org/10.1121/10.0001377 DB - PRIME DP - Unbound Medicine ER -
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