压电悬臂梁的涡激振动能量采集技术与流机电耦合模拟研究

Vortex-induced vibration (VIV) of piezoelectric cantilever beam can convert the kinetic energy of flow into electricity effectively, and this technique has become a new research focus in the field of ocean energy harvesting and utilization over the past few years. It is known that the lock-in effect existing in VIV phenomenon can significantly broaden the structural resonance region, and improve the flow energy harvesting efficiency. Therefore, it is essential to investigate the lock-in behavior of piezoelectric materials and the relevant mechanism. Taking into account the interactions between the flow, structure and electrical field, the present study aims to establish a three-dimensional loosely coupled finite element model for solving the hydro-mechanical-electric coupling system, which is expected to be applicable to the VIV problem of piezoelectric beam at high Reynolds numbers. Meanwhile, some laboratory experiments will be conducted for modeling validation purpose. Under these conditions of different locations, dimensions, orientations of free end and external resistances for piezoelectric beam in the wake of a bluff body, the verified numerical model will be employed to study the dynamic coupling mechanisms between the flow and beam, the VIV responses and the power output. By doing this, we try to reveal the lock-in behaviors of the beam, as well as the relationships between energy harvesting efficiency and structural resonance. This study will provide useful theoretical reference for optimum design of the piezoelectric ocean energy harvesting device.

利用压电悬臂梁的涡激振动可以有效地将流动能量转化为电能，该技术已成为近年来海洋能采集利用领域一个新的研究热点。涡激振动现象中存在的锁定效应能显著拓宽结构的共振区间，进而提高能量采集效率，因此研究压电结构的锁定行为及其内在机理具有重要意义。本项目研究将基于流体、结构和电场之间的相互作用，构建适合较高雷诺数流动情况下压电悬臂梁涡激振动特点的三维流机电弱耦合有限元模型，并通过模型实验验证其正确性。随后针对位于钝体尾流中的压电悬臂梁在不同位置、尺寸、自由端朝向以及外接电阻值情况下，应用构建的数值模型深入考察流场与压电悬臂梁的动力耦合机制、压电结构的涡激振动响应和能量输出特性，揭示不同影响因素作用下悬臂梁的锁定共振规律，阐明能量采集效率与结构共振之间的联系。本项目的研究成果可为压电海洋能采集装置的优化设计提供可靠的理论依据。

利用压电结构的机械振动进行流动能量采集的技术可以有效解决小型器件的供电问题。压电悬臂梁的涡激振动系统是一种常见的流动能量采集模型，因其制造简单、安装方便、使用寿命长、易于轻便化和微型化等优点，近年来已经成为新能源开发领域的一个研究热点。本研究首先构建了压电悬臂梁发电能力的理论计算模型和有限元数值模型，并对单晶片和双晶片压电梁进行了模拟验证与发电性能影响因素分析。研究结果表明压电悬臂梁的长宽比、厚度比及杨氏模量比对其发电能力都有较大影响。然后，针对压电悬臂梁的固有频率计算，给出了欧拉-伯努利梁理论估算模型和模态分析方法，并对压电悬臂结构在正弦激振力作用下的输出电压进行了谐响应分析，结果表明峰值电压出现在结构发生共振时。基于上述理论，设计了压电悬臂梁涡激振动能量采集物理模型并开展了水槽实验，主要探究了悬臂梁的几何尺寸、基板材质、来流速度以及悬臂梁与干扰圆柱之间的距离对输出电压的影响，揭示了电压响应和结构锁定共振之间的联系。实验发现，当设计的压电悬臂梁结构固有频率接近前方圆柱泄涡频率时，系统发生锁定共振，获得最优发电性能。在悬臂梁距干扰圆柱较近时，锁定共振区间显著变宽。最后，本研究构建了基于LES的高雷诺数流机电弱耦合有限元模型并进行了压电悬臂梁涡激振动能量采集数值模拟验证分析。本研究成果对海洋能压电采集装置的优化设计具有一定的科学意义和应用价值。