An experimental study of airfoil instability tonal noise with trailing edge serrations

Chong, Tze Pei; Joseph, Phillip

doi:10.1016/j.jsv.2013.06.033

Cited by 101 publications

(58 citation statements)

References 31 publications

(66 reference statements)

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“…The currently available approaches can be categorized as passive methods and active methods. The examples of the former one include the application of TE serrations, [10][11][12][13][14][15][16][17] TE brushes, 18,19 porous material, [20][21][22][23][24][25] surface treatments, [26][27][28][29] shape optimization and morphing, 30 etc. The efficiency of the passive methods is limited to a given range of conditions and out of this range they might introduce undesired losses.…”

Section: Nomenclaturementioning

confidence: 99%

Active Flow Control Methods for the Reduction of Trailing Edge Noise

Szoke

Azarpeyvand

2017

23rd AIAA/CEAS Aeroacoustics Conference

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General rightsThis document is made available in accordance with publisher policies. Please cite only the published version using the reference above. The possibility of trailing edge noise reduction using active flow control is addressed in this paper. The boundary layer is altered with the help of uniform perpendicular and inclined flow injection and suction on a long flat plate upstream of a sharp trailing edge. The flow quantities have been measured using particle image velocimetry, hot-wire anemometry, and the surface pressure fluctuations using flush mounted miniature pressure transducers. It was shown that the proposed flow control methods are capable of reducing the noise over a wide range of frequencies. It was also revealed that the perpendicular blowing is effective in shifting the energy containing turbulent structures away from the wall, resulting in a significant reduction in the surface pressure spectra. The inclined blowing control method was capable of further reducing the surface pressure spectra, while maintaining low input power requirement. The perpendicular suction control was shown to be effective in the reduction of pressure fluctuations in the mid frequency regions, which quickly penetrates to the lower frequency downstream. The inclined suction control has also lead to significant reductions in the surface pressure fluctuations over a wide range of frequencies, while the required suction rate was kept considerably low. It has also been shown that the proposed active flow control methods can reduce the spanwise correlation length of the turbulent structures near the trailing edge. In general, results have shown that all proposed active flow control techniques can effectively alter the boundary layer structure and reduce trailing edge noise. Nomenclature

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Section: Nomenclaturementioning

confidence: 99%

Active Flow Control Methods for the Reduction of Trailing Edge Noise

Szoke

Azarpeyvand

2017

23rd AIAA/CEAS Aeroacoustics Conference

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“…4a. Several familiar features pertaining to the laminar instability tonal noise are discernible: 1) the existence of velocity scaling laws U 1.5 and U 0.8 for the broadband hump and discrete tones, respectively [13,14]; and 2) the existence of the "ladder" structure. The result indicates that bypass boundary layer transition on the aerofoil surfaces was not triggered due to the low freestream turbulence intensity.…”

Section: A No Grid Case: Low Turbulence Jetmentioning

confidence: 99%

Aeroacoustic and Aerodynamic Performances of an Aerofoil Subjected to Sinusoidal Leading Edges

Chong

Vathylakis

McEwen

et al. 2015

21st AIAA/CEAS Aeroacoustics Conference

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This paper presents the preliminary results on the aeroacoustic and aerodynamic performances of a NACA65-(12)10 aerofoil subjected to 12 sinusoidal leading edges. The serration patterns of these leading edges are formed by cutting into the main body of the aerofoil, instead of extending the leading edges. Any of the leading edges, when attached to the main body of the aerofoil, will always result in the same overall chord length. The experiment was mainly performed in an aeroacoustic wind tunnel facility, although a separate aerodynamic type wind tunnel was also used for the force measurements. These sinusoidal leading edges were investigated for their effectiveness in suppressing the laminar instability tonal noise (trailing edge self-noise) and turbulence-leading edge interaction noise. The largest reduction in aerofoil noise tends to associate with the sinusoidal leading edge of the largest amplitude, and smallest wavelength. However, noticeable noise increase at high frequency is also observed for this combination of serration. In terms of the aerodynamic performance, increasing the serration wavelength tends to improve the stall angles, but the lift coefficient at the pre-stall regime is generally lower than that produced by the baseline leading edge. For a sinusoidal leading edge with large serration amplitude, the effect of the reduction in "lift-generating" surface is manifested in the significant reduction of the lift coefficients and lift curve slope. The sinusoidal leading edge that produces the best performance in the post-stall regime belongs to the largest wavelength and smallest amplitude, where the lift coefficients are shown to be better than the baseline leading edge. In conclusion, large amplitude and small wavelength is beneficial for noise reduction, whilst to maintain the aerodynamic lift a small amplitude and large wavelength is preferred.

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“…They also observed that the sharpness of the sawtooth affected the turbulent length scale and the turbulent intensity in the boundary layer region compared to the baseline case. The effects of serrations on airfoil's laminar flow instabilitiy noise was carried out by Chong and Joseph [28]. They showed that the sawtooth surface can trigger a bypass transition and prevent the boundary layer from becoming separated, subsequently reducing the two-dimensionality and preventing the amplification of the Tollmien-Schlichting waves.…”

Section: Introductionmentioning

confidence: 99%