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Leading edge serrations which reduce the noise of low-speed rotors
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In this article, the serrations were used as noise suppressors at rotor tip speeds less than 135 m/sec (444 ft/sec) than at higher speeds for two different size rotors.Abstract:
Acoustic effects of serrated brass strips attached near the leading edges of two different size rotors were investigated. The two bladed rotors were tested in hover. Rotor rotational speed, blade angle, serration shape, and serration position were varied. The serrations were more effective as noise suppressors at rotor tip speeds less than 135 m/sec (444 ft/sec) than at higher speeds. high frequency noise was reduced but the low frequency rotational noise was little affected. Noise reductions from 4 to 8 db overall sound pressure level and 3 to 17 db in the upper octave bands were achieved on the 1.52 m (5.0 ft) diameter rotor. Noise reductions up to 4 db overall sound pressure level were measured for the 2.59 m (8.5 ft) diameter rotor at some conditions.read more
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Journal ArticleDOI
Airfoil noise reductions through leading edge serrations
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Experimental and numerical investigation of turbulence-airfoil noise reduction using wavy edges
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Investigation of Acoustic Effects of Leading-Edge Serrations on Airfoils
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Morphometric characterisation of wing feathers of the barn owl Tyto alba pratincola and the pigeon Columba livia
Thomas Bachmann,Stephan Klän,Werner Baumgartner,Michael Klaas,Wolfgang Schröder,Hermann Wagner +5 more
TL;DR: The quantitative description of the feathers and the specific structures of owl feathers can be used as a model for the construction of a biomimetic airplane wing or, in general, as a source for noise-reducing applications on any surfaces subjected to flow fields.