Proceedings ArticleDOI
Broadband Noise Reduction With Trailing Edge Brushes
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In this article, a brush made of a single row of flexible polypropylene fibers is integrated in the trailing edge of a cambered airfoil, and far field acoustic measurements show a noise reduction potential reaching 3 dB on a wide frequency range.Abstract:
Airfoil broadband trailing edge noise is reduced by modification of the trailing edge geometry. A brush made of a single row of flexible polypropylene fibers is integrated in the trailing edge of a cambered airfoil. Far field acoustic measurements show a noise reduction potential reaching 3 dB on a wide frequency range. Due to high curvature of the incident flow, a secondary acoustic source partly masks the trailing edge noise reduction. Hot wire correlation measurements in the very near wake of the airfoil show that longitudinal as well as transversal length scales are affected by the brush. Span wise coherence length of boundary layer eddies falls off by 25 % in the presence of a brush in the adequate frequency range, possibly explaining a 1.3 dB contribution to the noise reduction mechanism. Boundary layer turbulence exhibits a preferred coherence length l y v on a wide frequency range. l y v /d ≈ 2, is considered a proper brush design law, d being the diameter of the brush.read more
Citations
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Journal ArticleDOI
Experimental characterization of the turbulent boundary layer over a porous trailing edge for noise abatement
Alejandro Rubio Carpio,Roberto Merino Martínez,Francesco Avallone,Daniele Ragni,Mirjam Snellen,Sybrand van der Zwaag +5 more
TL;DR: In this paper, the authors investigated the hydrodynamic and acoustic properties of a NACA 0018 chord with solid and porous trailing edge inserts and found that the porous inserts with higher permeability provided up to 11 dB noise attenuation with respect to the solid case for frequencies below a cross-over Strouhal number St = 0.26.
Journal ArticleDOI
Self-Noise Produced by an Airfoil with Nonflat Plate Trailing-Edge Serrations
TL;DR: In this article, the results of an experimental study aimed at reducing the airfoil self-noise by the trailing edge serration of four different sawtooth geometries (defined in the serration angle and length) were presented.
Proceedings ArticleDOI
An analytical investigation of trailing edge noise reduction using novel serrations
TL;DR: In this article, the authors investigated the passive control of trailing edge noise using complex periodic trailing edge serrations and showed that the noise reduction from serrated trailing edges is a sensitive function of the complexity of the serration geometry.
Proceedings ArticleDOI
Trailing edge noise of partially porous airfoils
Thomas F. Geyer,Ennes Sarradj +1 more
TL;DR: In this paper, a set of airfoils with porous trailing edges of varying chordwise extent were evaluated in an open jet wind tunnel, using a microphone array measurement technique and a deconvolution beamforming algorithm.
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