摘要
水下智能材料驱动柔性结构在机器鱼、水下航行器及精密医疗等领域具有广阔应用前景。本文研究了水下大振幅压电纤维(Macro Fiber Composite,MFC)致动柔性结构的非线性流体动力特性,建立了流固耦合振动模型,并进行了实验验证。通过参数化的二维CFD分析了不同特征振动频率及振幅下柔性结构周围流场的分布演化规律,发现随着柔性结构特征振幅增大,其周围流场逐渐出现了涡旋脱落及对流现象,且流体阻尼效应的非线性随之增强。提出了由特征振动频率和振幅共同确定的非线性修正流体动力函数解析表达式,分析结果表明:在小振幅情况下,修正流体动力函数虚部也就是流体阻尼效应随着特征振动频率的增大而减小;而当特征振幅增大到一定值后,流体阻尼效应随着特征振动频率的增大却呈现出先减小后增大的变化规律,具有强烈的非线性特性。开展了水下MFC致动柔性结构振动特性验证实验,证实柔性结构在MFC主动激励下的实测幅频、相频特性与理论预测结果基本一致,验证了所提修正流体动力函数表达式及流固耦合振动模型的有效性。
Oscillating underwater flexible structure actuated by smart materials are widely used in the fields of robotic fish,autono-mous underwater vehicle,precision medical instrument,and so on.In this paper,the nonlinear hydrodynamics of an underwater Macro Fiber Composite(MFC)-actuated flexible cantilever undergoing large amplitude vibration is studied.The fluid-structure coupled dynamic equation of the proposed structure is established.Parametric 2D CFD studies of the proposed structure at different characteristic frequencies and amplitudes are performed.The distribution and evolution of the flow field in the vicinity of the vibrat-ing structure are revealed.CFD results show that the vortex shedding,diffusion and convection phenomena which are responsible for the nonlinear hydrodynamic damping effect appear as the vibration amplitude increases.Then,a manageable expression for the revised hydrodynamic function governed by the interplay of the characteristic frequency and vibration amplitude is presented to mod-el the hydrodynamic load exerted on the flexible structure undergoing finite amplitude vibration.The imaginary part of the revised hydrodynamic function which accounts for the hydrodynamic damping effect decreases with the characteristic frequency for the small amplitude vibration.It first decreases then increases for the finite amplitude vibration,exhibiting a strong nonlinear behavior.Experimental results show that the measured frequency response spectrums of the proposed structure undergoing finite amplitude match well with the predicted results of the developed model.Thus,the validities of the developed hydrodynamic function and flu-id-structure coupled dynamic equation are demonstrated.
作者
杨浙栋
娄军强
陈特欢
崔玉国
魏燕定
李国平
YANG Zhe-dong;LOU Jun-qiang;CHEN Te-huan;CUI Yu-guo;WEI Yan-ding;LI Guo-ping(Zhejiang Provincial Key Laboratory of Part Rolling Technology,Faculty of Mechanical Engineering and Mechanics,Ningbo University,Ningbo 315211,China;Key Laboratory of Advanced Manufacturing Technology of Zhejiang Province,School of Mechanical Engineering,Zhejiang University,Hangzhou 310027,China)
出处
《振动工程学报》
EI
CSCD
北大核心
2024年第3期365-373,共9页
Journal of Vibration Engineering
基金
国家自然科学基金资助项目(52375103,51975517,52075273,51805276)
浙江省自然科学基金资助项目(LGF21E050002)
浙江省省属高校基本科研业务费专项资金资助项目(SJLY2021014)。
关键词
非线性流体动力学
流体动力函数
流固耦合振动
水下柔性结构
压电纤维
nonlinear hydrodynamics
hydrodynamic function
fluid-structure coupling vibration
underwater flexible structure
macro fiber composites(MFC)