翼近傍後流の外乱に対する応答 [in Japanese] Response of Airfoil Near-Wake to External Forcing [in Japanese]
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The response of an airfoil wake to acoustic forcing is examined experimentally for NACA0012 airfoil at moderate and high angles of attack, at a chord-Reynolds number Rc=23×104. At a moderate angle of attack α=10°, the flow is found to be highly receptive to acoustic forcings over a wide range of frequencies and the excited vortices can govern the downstream wake. At a stall angle α=16°, on the other hand, nearly periodic large-scale vortical structures appear and govern the wake without the forcing, indicating the appearance of the absolute instability in the near wake, not unlike that of bluff-body wakes. In this case, the small-amplitude external forcing can not control the vortex shedding except at and around the natural shedding frequency, suggesting that the stall is critically governed by the absolute (or global mode) instability under natural flow conditions without large-amplitude external forcings.
- Aeronautical and Space Sciences Japan
Aeronautical and Space Sciences Japan 45(522), 411-416, 1997-07
The Japan Society for Aeronautical and Space Sciences