Experimental Investigations in Low-Noise Trailing Edge Design.

Herr, Michaela; Dobrzynski, W.

doi:10.2514/1.11101

Cited by 167 publications

(108 citation statements)

References 10 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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“…A major factor for aircraft noise during landing is the noise generated by flow around the airframe. One way to lower that noise is to use porous surfaces, e.g., a porous trailing edge [3][4][5][6][7]. Ideally, the porous materials are supposed to bear mechanical loads.…”

Section: Introductionmentioning

confidence: 99%

Damage Behavior of Sintered Fiber Felts

Lippitz

Rösler

2015

Metals

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The reduction of aircraft noise is important due to a rising number of flights and the growth of urban centers close to airports. During landing, a significant part of the noise is generated by flow around the airframe. To reduce that noise porous trailing edges are investigated. Ideally, the porous materials should to be structural materials as well. Therefore, the mechanical properties and damage behavior are of major interest. The aim of this study is to show the change of structure and the damage behavior of sintered fiber felts, which are promising materials for porous trailing edges, under tensile loading using a combination of tensile tests and three dimensional computed tomography scans. By stopping the tensile test after a defined stress or strain and scanning the sample, it is possible to correlate structural changes and the development of damage to certain features in the stress-strain curve and follow the damage process with a high spatial resolution. Finally, the correlation between material structure and mechanical behavior is demonstrated.

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“…For the aforementioned applications, the most relevant mechanisms are related to the interaction of the turbulent boundary layer with the airfoil trailing edge, especially at low Mach numbers. 3 In the past, several passive noise-mitigation solutions have been proposed with the goal to alleviate this contribution, e.g., trailing-edge brushes, 4 sinusoidal and sawtooth serrations, [5][6][7][8][9][10][11][12] slits, 13,14 and randomly shaped trailing edges. 15 In the past decade, many analytical, [16][17][18][19] experimental, 5,9,11,20 and numerical studies 1,[21][22][23] have appointed sawtooth serrations as one of the most promising solutions.…”

Section: Introductionmentioning

confidence: 99%

Three-dimensional flow field over a trailing-edge serration and implications on broadband noise

2016

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The three-dimensional flow field over the suction side of a NACA 0018 airfoil with trailing-edge serrations was studied by means of time-resolved tomographic particle image velocimetry. Mean flow results show that the boundary layer thickness decreases along the streamwise direction with a corresponding reduction of the size of the turbulent structures developing over the suction side of the serrations. At a positive angle of attack, streamwise-oriented and counter-rotating vortices aligned with the edge of the serrations are found to be the main features of the mean flow field. Their formation is attributed to the pressure imbalance between the two sides of the airfoil and the mixing layer at the edge. They locally modify the effective angle seen by the turbulent flow approaching the serrated edge. This effect may contribute to the serration underperformance in terms of noise reduction reported in literature. The spatial distribution of the spectra of the source term of the Poisson equation, which relates the velocity field to pressure fluctuations, suggests that the contribution of the serrations to far-field broadband noise is a function of the streamwise location. This observation is congruent with the spectra of the wall-normal and spanwise velocity fluctuations, which typically show low intensity close to the tips of the individual serrations. It follows that analytical models must take into account the local contribution to the far-field noise induced by the streamwise variation of the hydrodynamic pressure on the serration surface.

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Experimental Investigations in Low-Noise Trailing Edge Design.

Cited by 167 publications

References 10 publications

Active Flow Control Methods for the Reduction of Trailing Edge Noise

Active Flow Control Methods for the Reduction of Trailing Edge Noise

Damage Behavior of Sintered Fiber Felts

Three-dimensional flow field over a trailing-edge serration and implications on broadband noise

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