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Phillip Joseph - One of the best experts on this subject based on the ideXlab platform.
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leading edge serrations for the reduction of aerofoil Self Noise at low angle of attack pre stall and post stall conditions
International Journal of Aeroacoustics, 2021Co-Authors: Giovanni Lacagnina, Bharathram Ganapathisubramani, Tze Pei Chong, Phillip Joseph, Paruchuri Chaitanya, Junghoon Kim, Tim Berk, Kwingso Choi, Seyed Mohammad Hasheminejad, Oksana StalnovAbstract:This paper addresses the usefulness of leading edge serrations for reducing aerofoil Self-Noise over a wide range of angles of attack. Different serration geometries are studied over a range of Reynolds number (Formula presented.). Design guidelines are proposed that permit Noise reductions over most angles of attack. It is shown that serration geometries reduces the Noise but adversely effect the aerodynamic performance suggesting that a trade-off should be sought between these two considerations. The Self-Noise performance of leading edge serrations has been shown to fall into three angle of attack (AoA) regimes: low angles where the flow is mostly attached, moderate angles where the flow is partially to fully separated, and high angles of attack where the flow is fully separated. Leading edge serrations have been demonstrated to be effective in reducing Noise at low and high angles of attack but ineffective at moderate angles. The Noise reduction mechanisms are explored in each of three angle regimes.
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leading edge serrations for the reduction of aerofoil Self Noise at low angle of attack pre stall and post stall conditions
International Journal of Aeroacoustics, 2021Co-Authors: Giovanni Lacagnina, Bharathram Ganapathisubramani, Tze Pei Chong, Phillip Joseph, Paruchuri Chaitanya, Junghoon Kim, Tim Berk, Kwingso Choi, Seyed Mohammad Hasheminejad, Oksana StalnovAbstract:This paper addresses the usefulness of leading edge serrations for reducing aerofoil Self-Noise over a wide range of angles of attack. Different serration geometries are studied over a range of Rey...
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leading edge serrations for the reduction of aerofoil separation Self Noise
AIAA CEAS Aeroacoustics Conference, 2017Co-Authors: Tze Pei Chong, Phillip Joseph, Giovanni Lacagnina, Seyed Mohammad Hasheminejad, Chaitanya C. Paruchuri, Oksana StalnovAbstract:This paper presents an experimental investigation into the use of LE serrations for the reduction of trailing edge Self-Noise, at least for the NACA-65 aerofoil family. It is shown that the leading edge serrations are able to reduce the Self-Noise in a low frequency range at small and negative angles of attack. The exact mechanism of this reduction is still not completely discovered, but the LE serrations are discovered able to modulate the mean velocity field and turbulent velocity spectrum in that range of frequencies, as well as to dampen the effect of the angle of attack on the pressure field and to reduce its coherence. We emphasise that this paper represents work in progress and further investigations are still necessary in order to completely understand the dynamics behind this reduction.
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performance and mechanism of sinusoidal leading edge serrations for the reduction of turbulence aerofoil interaction Noise
Journal of Fluid Mechanics, 2017Co-Authors: Paruchuri Chaitanya, S Narayanan, Jae Wook Kim, Phillip Joseph, Christina Vanderwel, Jacob M Turner, Bharathram GanapathisubramaniAbstract:This paper presents the results of a detailed experimental investigation into the effectiveness of sinusoidal leading edge serrations on aerofoils for the reduction of the Noise generated by the interaction with turbulent flow. A detailed parametric study is performed to investigate the sensitivity of the Noise reductions to the serration amplitude and wavelength. The study is primarily performed on flat plates in an idealized turbulent flow, which we demonstrate captures the same behaviour as when identical serrations are introduced onto 3D aerofoils. The influence on the Noise reduction of the turbulence integral length-scale is also studied. An optimum serration wavelength is identified whereby maximum Noise reductions are obtained, corresponding to when the transverse integral length-scale is roughly one-forth the serration wavelength. This paper proves that, at the optimum serration wavelength, adjacent valley sources are excited incoherently. One of the most important findings of this paper is that, at the optimum serration wavelength, the sound power radiation from the serrated aerofoil varies inversely proportional to the Strouhal number Sth=fh/U, where f, h and U are frequency, serration amplitude and flow speed, respectively. A simple model is proposed to explain this behaviour. Noise reductions are observed to generally increase with increasing frequency until the frequency at which aerofoil Self-Noise dominates the interaction Noise. Leading edge serrations are also shown to reduce trailing edge Self-Noise. The mechanism for this phenomenon is explored through PIV measurements. Finally, the lift and drag of the serrated aerofoil are obtained through direct measurement and compared against the straight edge baseline aerofoil. It is shown that aerodynamic performance is not substantially degraded by the introduction of the leading edge serrations on the aerofoil.
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performance and mechanism of sinusoidal leading edge serrations for the reduction of turbulence aerofoil interaction Noise
Journal of Fluid Mechanics, 2017Co-Authors: Paruchuri Chaitanya, S Narayanan, Jae Wook Kim, Phillip Joseph, Christina Vanderwel, Jacob M Turner, Bharathram GanapathisubramaniAbstract:This paper presents the results of a detailed experimental investigation into the effectiveness of sinusoidal leading edge serrations on aerofoils for the reduction of the Noise generated by the interaction with turbulent flow. A detailed parametric study is performed to investigate the sensitivity of the Noise reductions to the serration amplitude and wavelength. The study is primarily performed on flat plates in an idealized turbulent flow, which we demonstrate captures the same behaviour as when identical serrations are introduced onto three-dimensional aerofoils. The influence on the Noise reduction of the turbulence integral length scale is also studied. An optimum serration wavelength is identified whereby maximum Noise reductions are obtained, corresponding to when the transverse integral length scale is approximately one-fourth the serration wavelength. This paper proves that, at the optimum serration wavelength, adjacent valley sources are excited incoherently. One of the most important findings of this paper is that, at the optimum serration wavelength, the sound power radiation from the serrated aerofoil varies inversely proportional to the Strouhal number , where , and are frequency, serration amplitude and flow speed, respectively. A simple model is proposed to explain this behaviour. Noise reductions are observed to generally increase with increasing frequency until the frequency at which aerofoil Self-Noise dominates the interaction Noise. Leading edge serrations are also shown to reduce aerofoil Self-Noise. The mechanism for this phenomenon is explored through particle image velocimetry measurements. Finally, the lift and drag of the serrated aerofoil are obtained through direct measurement and compared against the straight edge baseline aerofoil. It is shown that aerodynamic performance is not substantially degraded by the introduction of the leading edge serrations on the aerofoil.
Soogab Lee - One of the best experts on this subject based on the ideXlab platform.
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aeroacoustic analysis of a wind turbine airfoil and blade on icing state condition
Journal of Renewable and Sustainable Energy, 2014Co-Authors: Byeongho Hwang, Seunghoon Lee, Taehyung Kim, Soogab LeeAbstract:An influences of iced airfoils on aerodynamic and aeroacoustic properties were studied to predict of the wind turbine Noise on icing state. In order to validate the aerodynamic performance, the experimental results and iced airfoils, which were studied by Jasinski et al. [“Wind turbine performance under icing state conditions,” AIAA Paper No. 97-0977, 1997], were used. Ice accretions on the two S809 wind turbine airfoils were predicted using the NASA LEWICE code. For analysis of boundary layer properties, the computational fluid dynamics was used when the Reynolds number is 1 × 106. To validate aerodynamic performances, lift coefficients were compared to the experimental result. The aeroacoustic analysis is estimated by summating the Turbulent inflow (TI) Noise and the airfoil Self-Noise. The airfoil Self-Noise is obtained using aerodynamics data such as a boundary layer thickness. Semi-empirical method proposed by Brooks et al. [Airfoil Self-Noise and Prediction (NASA reference publication 1218, 1989)] was used. The TI Noise is a dominant Noise source because of a complicated shape of leading edge on the iced airfoil. For considering leading edge shapes, therefore, TI Noise modeling proposed by Moriarty et al. [“Recent improvement of a semi-empirical aeroacoustic prediction code for wind turbines,” AIAA Paper 2004–3041, 2004; “Prediction of turbulent inflow and trailing-edge Noise for wind turbines,” AIAA Paper 2005–2881, 2005] was used. As a result, lift coefficients of the iced airfoils matched well experimental data by Jasinski et al. The sound pressure level was increased 2–4 dB from the clean airfoils. The analysis of wind turbine blades on icing state was conducted using the same method. The NREL Phase VI rotor was used as the baseline. Ice accretions on the two wind turbine blades were predicted using the LEWICE code. The overall sound pressure level was increased up to 2.6 dB from the clean wind turbine blade.
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aerodynamic and aeroacoustic analysis of a wind turbine airfoil on icing state condition
AFORE, 2013Co-Authors: Byeongho Hwang, Taehyung Kim, Soogab LeeAbstract:The influences of iced airfoils on aerodynamic and aeroacoustic properties were studied. In order to validate the aerodynamic performance, the experimental results and iced airfoils which were studied by W. J. Jasinski et al were used. Ice accretions on the two S809 wind turbine airfoils were predicted using the NASA LEWICE code. For analysis of aerodynamic performance, the computational fluid dynamics was used over the Reynolds number range 1-2 × 10 6 . To validate aerodynamic performances, lift and drag coefficients were compared to the experimental result. The aeroacoustic analysis is estimated summating TIN Noise and the airfoil Self-Noise. The airfoil Self-Noise is obtained using aerodynamics data such as a boundary layer thickness. Semi-empirical method proposed by Brooks et al was used. The turbulence inflow Noise(TIN) is a dominant Noise source because of a complicated shape of leading edge on the iced airfoil. For considering leading edge shapes, therefore, TIN modeling proposed by P. J. Moriarty et al was used. At the result, lift coefficients decreased 11%, 16% when angle of attack is 10 degree. The sound pressure level was increased 2 dB from the clean airfoils.
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aerodynamic Noise analysis of large horizontal axis wind turbines considering fluid structure interaction
Renewable Energy, 2012Co-Authors: Hogeon Kim, Seungmin Lee, Seunghoon Lee, Eunkuk Son, Soogab LeeAbstract:Aerodynamic Noise is one of the most serious barriers in wind energy development. To develop technologies for wind turbine Noise reduction and assessment, Noise needs to be predicted precisely with special consideration given to blade flexibility. The numerical tool, WINFAS, which can simulate fluid–structure interaction, consists of three parts: the first part, the Unsteady Vortex Lattice Method, analyzes aerodynamics; the second part, the Nonlinear Composite Beam Theory, analyzes structure; and the third part uses a semi-empirical formula to analyze airfoil Self-Noise and the Lowson’s formula to analyze turbulence ingestion Noise. In this study, using this numerical tool, the change in the Noise strength due to blade flexibility was examined. This research showed that elastic blades decreased broadband Noise because pitching motion reduced the angle of attack.
Bharathram Ganapathisubramani - One of the best experts on this subject based on the ideXlab platform.
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leading edge serrations for the reduction of aerofoil Self Noise at low angle of attack pre stall and post stall conditions
International Journal of Aeroacoustics, 2021Co-Authors: Giovanni Lacagnina, Bharathram Ganapathisubramani, Tze Pei Chong, Phillip Joseph, Paruchuri Chaitanya, Junghoon Kim, Tim Berk, Kwingso Choi, Seyed Mohammad Hasheminejad, Oksana StalnovAbstract:This paper addresses the usefulness of leading edge serrations for reducing aerofoil Self-Noise over a wide range of angles of attack. Different serration geometries are studied over a range of Rey...
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leading edge serrations for the reduction of aerofoil Self Noise at low angle of attack pre stall and post stall conditions
International Journal of Aeroacoustics, 2021Co-Authors: Giovanni Lacagnina, Bharathram Ganapathisubramani, Tze Pei Chong, Phillip Joseph, Paruchuri Chaitanya, Junghoon Kim, Tim Berk, Kwingso Choi, Seyed Mohammad Hasheminejad, Oksana StalnovAbstract:This paper addresses the usefulness of leading edge serrations for reducing aerofoil Self-Noise over a wide range of angles of attack. Different serration geometries are studied over a range of Reynolds number (Formula presented.). Design guidelines are proposed that permit Noise reductions over most angles of attack. It is shown that serration geometries reduces the Noise but adversely effect the aerodynamic performance suggesting that a trade-off should be sought between these two considerations. The Self-Noise performance of leading edge serrations has been shown to fall into three angle of attack (AoA) regimes: low angles where the flow is mostly attached, moderate angles where the flow is partially to fully separated, and high angles of attack where the flow is fully separated. Leading edge serrations have been demonstrated to be effective in reducing Noise at low and high angles of attack but ineffective at moderate angles. The Noise reduction mechanisms are explored in each of three angle regimes.
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performance and mechanism of sinusoidal leading edge serrations for the reduction of turbulence aerofoil interaction Noise
Journal of Fluid Mechanics, 2017Co-Authors: Paruchuri Chaitanya, S Narayanan, Jae Wook Kim, Phillip Joseph, Christina Vanderwel, Jacob M Turner, Bharathram GanapathisubramaniAbstract:This paper presents the results of a detailed experimental investigation into the effectiveness of sinusoidal leading edge serrations on aerofoils for the reduction of the Noise generated by the interaction with turbulent flow. A detailed parametric study is performed to investigate the sensitivity of the Noise reductions to the serration amplitude and wavelength. The study is primarily performed on flat plates in an idealized turbulent flow, which we demonstrate captures the same behaviour as when identical serrations are introduced onto 3D aerofoils. The influence on the Noise reduction of the turbulence integral length-scale is also studied. An optimum serration wavelength is identified whereby maximum Noise reductions are obtained, corresponding to when the transverse integral length-scale is roughly one-forth the serration wavelength. This paper proves that, at the optimum serration wavelength, adjacent valley sources are excited incoherently. One of the most important findings of this paper is that, at the optimum serration wavelength, the sound power radiation from the serrated aerofoil varies inversely proportional to the Strouhal number Sth=fh/U, where f, h and U are frequency, serration amplitude and flow speed, respectively. A simple model is proposed to explain this behaviour. Noise reductions are observed to generally increase with increasing frequency until the frequency at which aerofoil Self-Noise dominates the interaction Noise. Leading edge serrations are also shown to reduce trailing edge Self-Noise. The mechanism for this phenomenon is explored through PIV measurements. Finally, the lift and drag of the serrated aerofoil are obtained through direct measurement and compared against the straight edge baseline aerofoil. It is shown that aerodynamic performance is not substantially degraded by the introduction of the leading edge serrations on the aerofoil.
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performance and mechanism of sinusoidal leading edge serrations for the reduction of turbulence aerofoil interaction Noise
Journal of Fluid Mechanics, 2017Co-Authors: Paruchuri Chaitanya, S Narayanan, Jae Wook Kim, Phillip Joseph, Christina Vanderwel, Jacob M Turner, Bharathram GanapathisubramaniAbstract:This paper presents the results of a detailed experimental investigation into the effectiveness of sinusoidal leading edge serrations on aerofoils for the reduction of the Noise generated by the interaction with turbulent flow. A detailed parametric study is performed to investigate the sensitivity of the Noise reductions to the serration amplitude and wavelength. The study is primarily performed on flat plates in an idealized turbulent flow, which we demonstrate captures the same behaviour as when identical serrations are introduced onto three-dimensional aerofoils. The influence on the Noise reduction of the turbulence integral length scale is also studied. An optimum serration wavelength is identified whereby maximum Noise reductions are obtained, corresponding to when the transverse integral length scale is approximately one-fourth the serration wavelength. This paper proves that, at the optimum serration wavelength, adjacent valley sources are excited incoherently. One of the most important findings of this paper is that, at the optimum serration wavelength, the sound power radiation from the serrated aerofoil varies inversely proportional to the Strouhal number , where , and are frequency, serration amplitude and flow speed, respectively. A simple model is proposed to explain this behaviour. Noise reductions are observed to generally increase with increasing frequency until the frequency at which aerofoil Self-Noise dominates the interaction Noise. Leading edge serrations are also shown to reduce aerofoil Self-Noise. The mechanism for this phenomenon is explored through particle image velocimetry measurements. Finally, the lift and drag of the serrated aerofoil are obtained through direct measurement and compared against the straight edge baseline aerofoil. It is shown that aerodynamic performance is not substantially degraded by the introduction of the leading edge serrations on the aerofoil.
Paruchuri Chaitanya - One of the best experts on this subject based on the ideXlab platform.
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leading edge serrations for the reduction of aerofoil Self Noise at low angle of attack pre stall and post stall conditions
International Journal of Aeroacoustics, 2021Co-Authors: Giovanni Lacagnina, Bharathram Ganapathisubramani, Tze Pei Chong, Phillip Joseph, Paruchuri Chaitanya, Junghoon Kim, Tim Berk, Kwingso Choi, Seyed Mohammad Hasheminejad, Oksana StalnovAbstract:This paper addresses the usefulness of leading edge serrations for reducing aerofoil Self-Noise over a wide range of angles of attack. Different serration geometries are studied over a range of Rey...
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leading edge serrations for the reduction of aerofoil Self Noise at low angle of attack pre stall and post stall conditions
International Journal of Aeroacoustics, 2021Co-Authors: Giovanni Lacagnina, Bharathram Ganapathisubramani, Tze Pei Chong, Phillip Joseph, Paruchuri Chaitanya, Junghoon Kim, Tim Berk, Kwingso Choi, Seyed Mohammad Hasheminejad, Oksana StalnovAbstract:This paper addresses the usefulness of leading edge serrations for reducing aerofoil Self-Noise over a wide range of angles of attack. Different serration geometries are studied over a range of Reynolds number (Formula presented.). Design guidelines are proposed that permit Noise reductions over most angles of attack. It is shown that serration geometries reduces the Noise but adversely effect the aerodynamic performance suggesting that a trade-off should be sought between these two considerations. The Self-Noise performance of leading edge serrations has been shown to fall into three angle of attack (AoA) regimes: low angles where the flow is mostly attached, moderate angles where the flow is partially to fully separated, and high angles of attack where the flow is fully separated. Leading edge serrations have been demonstrated to be effective in reducing Noise at low and high angles of attack but ineffective at moderate angles. The Noise reduction mechanisms are explored in each of three angle regimes.
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performance and mechanism of sinusoidal leading edge serrations for the reduction of turbulence aerofoil interaction Noise
Journal of Fluid Mechanics, 2017Co-Authors: Paruchuri Chaitanya, S Narayanan, Jae Wook Kim, Phillip Joseph, Christina Vanderwel, Jacob M Turner, Bharathram GanapathisubramaniAbstract:This paper presents the results of a detailed experimental investigation into the effectiveness of sinusoidal leading edge serrations on aerofoils for the reduction of the Noise generated by the interaction with turbulent flow. A detailed parametric study is performed to investigate the sensitivity of the Noise reductions to the serration amplitude and wavelength. The study is primarily performed on flat plates in an idealized turbulent flow, which we demonstrate captures the same behaviour as when identical serrations are introduced onto 3D aerofoils. The influence on the Noise reduction of the turbulence integral length-scale is also studied. An optimum serration wavelength is identified whereby maximum Noise reductions are obtained, corresponding to when the transverse integral length-scale is roughly one-forth the serration wavelength. This paper proves that, at the optimum serration wavelength, adjacent valley sources are excited incoherently. One of the most important findings of this paper is that, at the optimum serration wavelength, the sound power radiation from the serrated aerofoil varies inversely proportional to the Strouhal number Sth=fh/U, where f, h and U are frequency, serration amplitude and flow speed, respectively. A simple model is proposed to explain this behaviour. Noise reductions are observed to generally increase with increasing frequency until the frequency at which aerofoil Self-Noise dominates the interaction Noise. Leading edge serrations are also shown to reduce trailing edge Self-Noise. The mechanism for this phenomenon is explored through PIV measurements. Finally, the lift and drag of the serrated aerofoil are obtained through direct measurement and compared against the straight edge baseline aerofoil. It is shown that aerodynamic performance is not substantially degraded by the introduction of the leading edge serrations on the aerofoil.
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performance and mechanism of sinusoidal leading edge serrations for the reduction of turbulence aerofoil interaction Noise
Journal of Fluid Mechanics, 2017Co-Authors: Paruchuri Chaitanya, S Narayanan, Jae Wook Kim, Phillip Joseph, Christina Vanderwel, Jacob M Turner, Bharathram GanapathisubramaniAbstract:This paper presents the results of a detailed experimental investigation into the effectiveness of sinusoidal leading edge serrations on aerofoils for the reduction of the Noise generated by the interaction with turbulent flow. A detailed parametric study is performed to investigate the sensitivity of the Noise reductions to the serration amplitude and wavelength. The study is primarily performed on flat plates in an idealized turbulent flow, which we demonstrate captures the same behaviour as when identical serrations are introduced onto three-dimensional aerofoils. The influence on the Noise reduction of the turbulence integral length scale is also studied. An optimum serration wavelength is identified whereby maximum Noise reductions are obtained, corresponding to when the transverse integral length scale is approximately one-fourth the serration wavelength. This paper proves that, at the optimum serration wavelength, adjacent valley sources are excited incoherently. One of the most important findings of this paper is that, at the optimum serration wavelength, the sound power radiation from the serrated aerofoil varies inversely proportional to the Strouhal number , where , and are frequency, serration amplitude and flow speed, respectively. A simple model is proposed to explain this behaviour. Noise reductions are observed to generally increase with increasing frequency until the frequency at which aerofoil Self-Noise dominates the interaction Noise. Leading edge serrations are also shown to reduce aerofoil Self-Noise. The mechanism for this phenomenon is explored through particle image velocimetry measurements. Finally, the lift and drag of the serrated aerofoil are obtained through direct measurement and compared against the straight edge baseline aerofoil. It is shown that aerodynamic performance is not substantially degraded by the introduction of the leading edge serrations on the aerofoil.
Tze Pei Chong - One of the best experts on this subject based on the ideXlab platform.
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leading edge serrations for the reduction of aerofoil Self Noise at low angle of attack pre stall and post stall conditions
International Journal of Aeroacoustics, 2021Co-Authors: Giovanni Lacagnina, Bharathram Ganapathisubramani, Tze Pei Chong, Phillip Joseph, Paruchuri Chaitanya, Junghoon Kim, Tim Berk, Kwingso Choi, Seyed Mohammad Hasheminejad, Oksana StalnovAbstract:This paper addresses the usefulness of leading edge serrations for reducing aerofoil Self-Noise over a wide range of angles of attack. Different serration geometries are studied over a range of Reynolds number (Formula presented.). Design guidelines are proposed that permit Noise reductions over most angles of attack. It is shown that serration geometries reduces the Noise but adversely effect the aerodynamic performance suggesting that a trade-off should be sought between these two considerations. The Self-Noise performance of leading edge serrations has been shown to fall into three angle of attack (AoA) regimes: low angles where the flow is mostly attached, moderate angles where the flow is partially to fully separated, and high angles of attack where the flow is fully separated. Leading edge serrations have been demonstrated to be effective in reducing Noise at low and high angles of attack but ineffective at moderate angles. The Noise reduction mechanisms are explored in each of three angle regimes.
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leading edge serrations for the reduction of aerofoil Self Noise at low angle of attack pre stall and post stall conditions
International Journal of Aeroacoustics, 2021Co-Authors: Giovanni Lacagnina, Bharathram Ganapathisubramani, Tze Pei Chong, Phillip Joseph, Paruchuri Chaitanya, Junghoon Kim, Tim Berk, Kwingso Choi, Seyed Mohammad Hasheminejad, Oksana StalnovAbstract:This paper addresses the usefulness of leading edge serrations for reducing aerofoil Self-Noise over a wide range of angles of attack. Different serration geometries are studied over a range of Rey...
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leading edge serrations for the reduction of aerofoil separation Self Noise
AIAA CEAS Aeroacoustics Conference, 2017Co-Authors: Tze Pei Chong, Phillip Joseph, Giovanni Lacagnina, Seyed Mohammad Hasheminejad, Chaitanya C. Paruchuri, Oksana StalnovAbstract:This paper presents an experimental investigation into the use of LE serrations for the reduction of trailing edge Self-Noise, at least for the NACA-65 aerofoil family. It is shown that the leading edge serrations are able to reduce the Self-Noise in a low frequency range at small and negative angles of attack. The exact mechanism of this reduction is still not completely discovered, but the LE serrations are discovered able to modulate the mean velocity field and turbulent velocity spectrum in that range of frequencies, as well as to dampen the effect of the angle of attack on the pressure field and to reduce its coherence. We emphasise that this paper represents work in progress and further investigations are still necessary in order to completely understand the dynamics behind this reduction.
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on the aeroacoustic and flow structures developed on a flat plate with a serrated sawtooth trailing edge
Journal of Sound and Vibration, 2015Co-Authors: Tze Pei Chong, Alexandros VathylakisAbstract:Abstract Results of an experimental study on turbulent flow over a flat plate with a serrated sawtooth trailing edge are presented in this paper. After tripping the boundary layer to become turbulent, the broadband Noise sources at the sawtooth serrated trailing edge is studied by several experimental techniques. Broadband Noise reduction by the serrated sawtooth trailing edge can be realistically achieved in the flat plate configuration. The variations of wall pressure power spectral density and the spanwise coherence (which relates to the spanwise correlation length) in a sawtooth trailing edge play a minor role in the mechanisms underpinning the reduction of Self Noise radiation. Conditional-averaging technique was applied in the boundary layer data where a pair of pressure-driven oblique vortical structures near the sawtooth side edges is identified. In the current flat plate configuration, the interaction between the vortical structures and the local turbulent boundary layer results in a redistribution of the momentum transport and turbulent shear stress near the sawtooth side edges as well as the sawtooth tip, thus affecting the efficiency of Self Noise radiation.
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Poro-Serrated Trailing-Edge Devices for Airfoil Self-Noise Reduction
AIAA Journal, 2015Co-Authors: Tze Pei Chong, Alexandros Vathylakis, Phillip JosephAbstract:This paper represents the continuation of the works previously published in Chong et al. (“Self-Noise Produced by an Airfoil with Nonflat Plate Trailing-Edge Serrations,” AIAA Journal, Vol. 51, No. 11, 2013, pp. 2665–2677), who used several nonflat plate serrated trailing edges for the reduction of airfoil Self-Noise. The poro-serrated concept developed in the current work improves substantially the overall Noise performance of the nonflat plate trailing-edge serration type. The use of porous metal, synthetic foams, or thin brush bundles to fill the gaps between adjacent members of the sawtooth can completely suppress the bluntness-induced vortex shedding tonal Noise. Most important, up to 7 dB turbulent boundary layer–trailing-edge broadband Noise reduction can simultaneously be achieved without compromising the aerodynamic performances in lift and drag. The poro-serrated trailing edges do not cause any Noise increase throughout the frequency range investigated here. The reduction of the turbulent broadb...