D112 翼端流れの制御による翼騒音への影響(風力制御,OS-2 自然エネルギー(2),一般講演,地球温暖化防止と動力エネルギー技術)

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In this paper, we discuss effects on aerodynamic sound generated from an NACA0012 airfoil by the airfoil tip flows mainly at a Reynolds number of three times ten to the fifth and angle of attack of lifting condition. Some results of far-field sound spectra suggest that tip flow noise affect the sound of frequency range of 2.5 kHz to 8 kHz. Accordingly, we investigated unsteady flows around the airfoil tip by hotwire measurements and obtained some possibilities of noise reduction by reduction tip flows rolling up or its fluctuation from pressure side to suction side from the results that it was observed of high turbulence on the same range of frequency of velocity in the tip flows. Then, it was cleared that the appropriate flat plate could reduce the tip flows rolling up and the turbulence level, and could reduce the noise level of 3 dB (Max.) in the frequency range of 5 kHz to 8 kHz.
社団法人日本機械学会の論文
2008-06-18