关键词: 水下柔性结构, 仿鱼体波振动, 压电纤维, 流场分布特性, 计算流体动力学

Abstract: 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.

Key words: underwater flexible structure, vibration mimicking fish body wave, macro fiber composites(MFC), flow field distribution characteristics, computational fluid dynamics(CFD)