弹性支撑斑海豹胡须模型单自由度流致振动实验研究
SINGLE DEGREE-OF-FREEDOM FLOW-INDUCED VIBRATION OF AN ELASTICALLY-SUPPORTED HARBOR SEAL WHISKER MODEL: AN EXPERIMENTAL STUDY
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摘要: 斑海豹依靠其具有波状外形的胡须, 可感知猎物尾迹流场中的涡流, 进而循迹追踪. 对斑海豹胡须感知涡流特征的机制进行研究具有重要的科学意义和应用价值. 本文根据斑海豹胡须的外形参数, 制作了1:30的实验模型, 在水槽中研究了均匀流场和尾迹流场中单个胡须模型和胡须模型阵列的单自由度流致振动特性, 分析了模型振动响应与涡流特征的关联. 结果表明, 在均匀流场中, 零攻角条件下, 胡须的波状外形具有显著的抑振作用, 胡须模型在一定的折合流速范围内具有较低的振动幅值; 而当来流攻角较大时(
\alpha \geqslant 30^ \circ ), 振幅显著提高. 在固定圆柱形成的尾迹流场中, 胡须模型在一定的圆柱间距范围内发生大幅振动, 振动频率与尾流的泄涡频率锁定, 表现为明显的双峰模式, 这与均匀流场中胡须模型的单频振动模式明显不同. 尾迹流场中, 胡须模型的振动幅值受来流条件影响大, 但振动频率较为稳定. 在均匀流场和尾迹流场中, 除个别折合流速外, 阵列布置胡须模型的振动幅值和频率与单个胡须模型相近, 相邻胡须模型之间相互干扰不显著.Abstract: Depending on its wave-shaped whiskers, the harbor seal can identify the vortex characteristics of the wake flow of its prey and trace them. Thus, it is of important scientific significance and practical value to investigate the identification mechanisms of the harbor seal whiskers. In this study, a 1:30 scaled experimental whisker model was fabricated based on the geometric parameters of a harbor seal whisker, and the one degree-of-freedom flow-induced vibrations of a single whisker model and an array of whisker models in uniform flow and wake flow were investigated. The correlation of the vibration responses of the whisker model and the vortex characteristics was analyzed. It was found that owing to the wavy shape of the whisker model, the vibration of the whisker model at the zero angle-of-attack is significantly suppressed in uniform flow, and the whisker model has a very low vibration amplitude in a certain range of the reduced velocity. However, when the angle-of-attack is relatively large (\alpha \geqslant 30^ \circ ), the vibration amplitude is significantly augmented. In the wake flow of a stationary circular cylinder, large-amplitude vibrations of the whisker model happen in a certain range of distance from the cylinder, and the vibration frequency locks on the vortex-shedding frequency of the wake flow. Different to the single-frequency vibration of the whisker model in uniform flow, the vibration frequency of the whisker model in wake flow shows a two-peak mode. In wake flow, the vibration amplitude of the whisker model is significantly affected by flow conditions, but the vibration frequency of the whisker model is relatively stable. In uniform flow and wake flow, the vibration amplitude and frequency of an array of whisker models are similar to those of a single whisker model, except at several reduced velocities, which indicates that the interference between the whisker models in a whisker array is not significant.