压电纤维致动柔性结构的仿鱼体波振动特性及流场分布研究

Vibration Mimicking Fish Body Wave and Flow Distribution of Underwater Flexible Structure with Resonant Actuation of Macro Fiber Composites

提出利用压电纤维(MFC)致动柔性结构的二阶振动模态来模仿鲹科鱼类的鱼体波运动。基于假设模态法求解智能柔性结构的前三阶振型,实验测得水下柔性结构的二阶振型,验证了智能柔性结构的二阶振型逼近鲹科鲈鱼的鱼体波。采用计算流体动力学(CFD)分析了柔性结构周围流线及压力分布情况,结果表明:二阶振动行为下,柔性结构节点前后流线方向相反;两侧流场始终存在两组高、低压集中区域,且节点前后的压力集中区域分布相反;柔性结构两侧始终存在正压梯度,其中向前的压力分量为柔性结构提供持续的推进力,而节点前后压力分量产生的侧向力方向相反,部分抵消,增强了柔性结构的侧向稳定性。研究结果为水下仿生推进器的设计和性能分析提供了重要参考。

This paper utilized the unique underwater vibration properties of smart flexible structures to explore the body wave motion of carangiform fish,greatly impacting the prototype design and analysis of next-generation underwater vehicles.The second-order vibration mode shape of MFC-actuated flexible structures was employed to mimic the fish body wave motion of carangiform fish.The multiple normalized mode shapes of the MFC-actuated flexible structures were obtained using the assumed mode method,and the actual underwater second-order mode shape of the MFC-actuated structures was obtained experimentally.This verifies that the second mode shape of the flexible structures approximates the fish body wave of the carangiform fish.The distributions of the instantaneous velocity streamlines and concentrated pressure regions were revealed using CFD.Streamlines both for the inflow and outflow of the oscillating structure surfaces were observed from the simulation.The results show that:the flow directions before and after the node on the flexible structure second-order resonant states were opposite.Meanwhile,two pairs of high and low concentrated pressure regions are always on both sides of the oscillating structures.And the distributions of the high and low pressure regions are opposite before and after the node.In summary,positive pressure gradients always exist across the flexible structures,and the forward pressure component provides suggestive thrust for the oscillating flexible structures.Meanwhile,the lateral forces before and after the node induced by the pressure are in the opposite direction and are partially canceled out.Consequently,the lateral stability of the oscillating structures was enhanced.These results may benefit the design and performance improvement of underwater bionic propulsors and robotic fish.