Abstract This paper presents an experimental investigation aimed at characterizing the kinematics of a pitching-heaving aeroelastic wing placed downstream of a rectangular bluff body. The influence of the bluff body wake on the wing is twofold: a viscous wake which produces a velocity deficit downstream and an oscillating induced velocity field due to periodic vortex shedding. The latter effect is the focus of this paper, specifically, the interaction between the wake frequency and the wing limit cycle oscillation (LCO) frequency. Wind tunnel experiments showed that the presence of the upstream bluff body causes modulation of the LCO amplitude. The modulation resembles a beat phenomenon, however the modulation frequency is related to the third harmonic of f L C O rather than the fundamental frequency. The modulation behavior also differs from that of a beat in that the spectral content contains sideband frequencies, characteristic of a multiplication between a carrier wave and a modulation wave rather than a simple sinusoidal superposition. Additionally, the streamwise spacing between the bluff body and the wing significantly influences the wing kinematics, with a closer spacing between the two bodies increasing the intensity of the amplitude modulation. For shedding frequencies sufficiently close to the LCO third harmonic, reducing this streamwise distance was shown to induce an alternation between two distinct modes of amplitude modulation, each with its own intensity and frequency.

中文翻译：

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钝体尾流中气动弹性机翼的极限循环表征

摘要 本文提出了一项实验研究，旨在表征放置在矩形钝体下游的纵摇气动弹性机翼的运动学特性。钝体尾流对机翼的影响是双重的：粘性尾流在下游产生速度不足，以及由于周期性涡旋脱落而引起的振荡诱导速度场。后一种效应是本文的重点，特别是尾流频率与机翼极限周期振荡（LCO）频率之间的相互作用。风洞实验表明上游钝体的存在会导致 LCO 幅度的调制。调制类似于拍频现象，但调制频率与 f LCO 的三次谐波有关，而不是与基频有关。调制行为也不同于拍频，因为频谱内容包含边带频率，这是载波和调制波之间相乘的特征，而不是简单的正弦叠加。此外，钝体和机翼之间的流向间距显着影响机翼运动学，两个主体之间的间距更近会增加幅度调制的强度。为了使频率足够接近 LCO 三次谐波，减少这种流向距离会引起两种不同的幅度调制模式之间的交替，每种模式都有自己的强度和频率。载波和调制波之间的乘法特征，而不是简单的正弦叠加。此外，钝体和机翼之间的流向间距显着影响机翼运动学，两个主体之间的间距更近会增加幅度调制的强度。为了使频率足够接近 LCO 三次谐波，减少这种流向距离会引起两种不同的幅度调制模式之间的交替，每种模式都有自己的强度和频率。载波和调制波之间的乘法特征，而不是简单的正弦叠加。此外，钝体和机翼之间的流向间距显着影响机翼运动学，两个主体之间的间距更近会增加幅度调制的强度。为了使频率足够接近 LCO 三次谐波，减少这种流向距离会引起两种不同的幅度调制模式之间的交替，每种模式都有自己的强度和频率。