翼端流れの制御による翼騒音への影響(自然エネルギー,<特集>第13回動力・エネルギー技術シンポジウム)

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In this paper, we discuss effects on aerodynamic sound which is generated from NACA 0012 airfoil tip flows at a Reynolds number of 3×10^5 under the lifting condition. Far-field sound spectra indicate that the tip flows contribute to the sound of the frequency range of 2.5kHz to 8kHz. Accordingly, we investigate the relation between unsteady flows around the airfoil tip and the aerodynamic sound in this frequency rage by using a hotwire and a non-directional microphone. And we obtain some possibilities of noise reduction by the control of the tip flows rolling up from pressure side to suction side or the control of its fluctuation, from the results that large disturbances can be seen in the distributions of the velocity fluctuation integrated with above mentioned frequency range. Then, we clear that the appropriate flat plate can not only reduce the tip flows rolling up and its turbulence level, but also reduce the noise level of 3dB (Max.) in the frequency range of 5kHz to 8kHz.
社団法人日本機械学会の論文
2009-03-25