Abstract A particular behaviour is observed in the pitch-heave stall flutter of a NACA0012 airfoil at transitional chord-based Reynolds numbers during lock-in. When the air speeds is such that the airfoil oscillates at the pitch structural natural frequency, and the structural natural frequencies of the two motions are close and their ratio ω (= f h ∕ f θ ) is smaller than 1, the system exhibits a beating phenomenon in both pitching and heaving motions. The modulated amplitude of the two motions presents a phase shift allowing a feedback energy transfer alternatively from pitch to heave and from heave to pitch. Through this energy exchange, the limit cycle oscillation (LCO) is maintained with two frequencies. This phenomenon fades when the ratio ω become greater than one.

中文翻译：

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锁频2DOF失速颤振中的跳动现象

摘要 在锁定期间，在基于过渡弦的雷诺数下，NACA0012 翼型的俯仰-升沉失速颤振中观察到了一种特殊行为。当风速使得翼型以俯仰结构固有频率振荡，且两种运动的结构固有频率接近且它们的比值ω(= fh ∕ f θ )小于1时，系统表现出跳动现象在俯仰和起伏运动中。两种运动的调制幅度呈现相移，允许反馈能量交替地从俯仰到升沉和从升沉到俯仰传递。通过这种能量交换，极限循环振荡 (LCO) 以两个频率保持。当比率 ω 大于 1 时，这种现象就会消失。