104 NACA翼から発生する広帯域騒音に及ぼすはく離流れの影響(空力騒音の解析)

概要

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To clarify the mechanism of the broadband noise generated by the separated flow around a NACA series blade is aimed. The relation between the angle of attack and the broadband noise of the blade are analyzed by the wind tunnel experiment and a commercial CFD code. In the case of rear surface separation, the separated vortex that has a large scale structure in the direction of the blade chord is transformed to the vortical structure that has concentrated to the trailing edge with the increase of the angle of attack. Then the broadband noise level becomes small according to the vortex scale in the blade chord. The separation vortex of the low pressure is formed at the vicinity of the trailing edge when the flow is separated at the leading edge. The pressure fluctuation on the blade surface at the vicinity of trailing edge becomes large by the rotation of the vortex in the wake. The broadband noise level increases with the increase of the pressure fluctuation and the expansion of the correlation length by the vortex scale when the flow is separated at the leading edge.
2009-07-08