NACA 翼周りのはく離渦と空力騒音の関係

概要

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To clarify the mechanism of the aerodynamic noise generated by the separated vortex around a NACA blade is aimed. The relation between the angle of attack and the aerodynamic 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 aerodynamic noise level becomes small according to the vortex scale in the blade chord. The separated vortex 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 vortex in the wake. The aerodynamic noise level becomes large 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.