Measurement of the noise generation at the trailing edge of porous airfoils

Geyer, Thomas; Sarradj, Ennes; Fritzsche, Christoph

doi:10.1007/s00348-009-0739-x

Cited by 255 publications

(214 citation statements)

References 36 publications

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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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“…To reduce the turbulent boundary layer trailing edge noise, various passive airfoil noise control methods have been developed, such as trailing edge serrations [5,[8][9][10][11][12][13][14][15][16][17][18][19][20][21], trailing edge brushes [22][23][24], porous trailing edge [25][26][27][28][29][30], airfoil shape optimization [31,32], trailing edge morphing [33,34] and more recently upstream surface treatment [35][36][37]. It was shown both analytically [8][9][10][11][12] and experimentally [5,[13][14][15][16][17][18][19][20][21] that trailing edge noise levels can be reduced by modifying the trailing edge geometry with serrations so that the flow disturbances are scattered into sound with reduced efficiency.…”

Section: Introductionmentioning

confidence: 99%

Effects of Streamwise Surface Treatments on Trailing Edge Noise Reduction

Afshari

Azarpeyvand

Dehghan

et al. 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. Full terms of use are available: http://www.bristol.ac.uk/pure/about/ebr-terms The use of surface treatments as a passive flow control method for trailing edge noise reduction is considered in this paper. In order to investigate the effects of different types of surface treatments on surface pressure fluctuations, eddy convection velocity and spanwise length scale, a long flat-plate model, equipped with several streamwise and spanwise surface pressure microphones has been designed and built. Measurements have been carried out for a variety of 2D and 3D surface treatments. The flow behavior downstream of the surface treatments is also studied by employing a single probe hotwire anemometer. Results indicated that the use of finlets with coarse spacing leads to a favorable reduction in PSD at mid to high frequencies and an undesirable increase in spanwise length scale. In the case of finlets with fine spacing, the high frequency pressure fluctuations have been effectively suppressed and the spanwise length-scale has been reduced, but with a penalty of low to mid frequency surface pressure elevation. Furthermore, it is found that the ratio of the finlets spacing to the boundary layer thickness is a critical parameter for achieving maximum surface pressure PSD reduction and the finlets spacing should be in the order of the boundary layer inner region. It has also been shown that the proposed novel 3D surface treatments have better aeroacoustic performance than the standard 2D ones in terms of the reduction in the surface pressure power spectral density, the longitudinal and lateral coherence and eddy convection velocity.

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“…There has been much interest recently in developing methods aimed at reducing trailing edge broadband noise, such as serrated edges [1][2][3], porous surfaces [4] and brushes [5][6]. These passive methods have been demonstrated experimentally in low speed rig tests to afford levels of radiated noise reduction of roughly between 2 dB and 6 dB.…”

Section: Introductionmentioning

confidence: 99%