柔性水翼流致弯曲-扭转振动响应特性及耦合物理机制

The flexible structures which are manufactured by self-adaptive composites are widely utilized in aerospace and wind engineering. However, many of the strategies employed for aerospace applications cannot be easily applied for maritime applications. For the structures with composite materials, the unsteady hydrodynamic loads will cause significant bend-twist deformation and flow-induced vibration. The interactions of the structure and flow are often very complex in this phenomenon, which need to be further studied. This project investigates the characteristics of flow-induced bend-twist vibration responses of flexible hydrofoil and the mechanism of fluid-structure interaction by means of numerical simulation and experimental observation. In order to understand the key factors which affect the vibration response and hydrodynamic performance of the flexible hydrofoil， the deformation law of flow-induced bending and twisting vibration, as well as the characteristics of lift and drag will be investigated at first. The interaction between structure characteristics of flexible hydrofoil, vibration responses and separation of boundary layer, wake vortex patterns will be analyzed intensively. Then the physical mechanism of the fluid-solid interaction for flow-induced bend-twist coupling vibration of flexible hydrofoil will be clarified. Finally, the control and suppression method for flow-induced vibration of flexible hydrofoil will be obtained. The proposed project has high scientific and academic values in advancing the fluid-structure interaction dynamics theory and control methods of flow-induced vibration of flexible structures, as well as provides theoretical foundations for the design and operation for hydraulic machinery.

柔性自适应复合材料结构已广泛应用于航空航天和风力工程领域，然而其许多先进技术和方法却不适用于水力机械设计及应用。复合材料结构在非定常水动力载荷作用下会发生弯曲-扭转变形和流致振动，流固耦合过程非常复杂，涉及许多科学上的难题，存在大量的问题亟需进一步深入研究。本项目采用数值模拟和实验观测相结合的方法，研究柔性水翼流致弯曲-扭转振动响应特性及其流固耦合物理机制，获得柔性水翼流致弯扭变形规律及升阻力特性，明确影响水翼流致弯扭振动响应及水动力特性的关键因素，深入分析柔性水翼结构特性、流致振动幅频响应与边界层分离、尾流旋涡形态的相互关系，揭示流致弯扭振动流固耦合物理本质，获取柔性水翼流致振动控制方法及减振措施。研究结果不仅对丰富和发展流固耦合动力学理论及柔性结构振动控制利用方法具有非常重要的学术意义，还可为水力机械及动力装备的设计和运行提供理论依据和技术基础。

柔性复合材料水翼在受到非定常水动力载荷的作用时会发生明显的弯扭变形和流致振动。水翼流致弯曲-扭转振动流固耦合过程非常复杂，涉及许多科学上的难题。本项目采用数值模拟和实验观测相结合的方法，研究柔性水翼流致弯曲-扭转振动响应特性及耦合物理机制；获得了不同来流速度、水翼攻角等对水翼弯扭位移变化规律和振动频率分布的影响；得到了水翼幅频响应与边界层分离、尾涡形态的关系；揭示了柔性水翼流致弯扭耦合响应流固耦合物理机制。主要结论如下：（1）攻角α和来流速度对固定水翼力学响应及近尾流结构特性产生明显影响，时均升力系数在α=10°时达到最小，时均阻力系数随α增加而增加；可观察到2S（低速）、2S*（中、高速）和U型（低攻角且高速）尾涡模态。（2）当限制水翼仅发生弯曲时，在α=10°幅值极低，当α>10°时，弯曲振幅随折减速度逐渐降低并保持稳定；当限制水翼仅发生扭转时，15°<α≤35°内，扭转幅度在U*>10后随U*的增加快速升高，且会出现频率锁定。（3）当柔性水翼发生弯扭耦合响应时，低折减速度下水翼仅出现极小弯曲振动；当水翼出现明显弯曲时，弯曲振幅随α增加而增加；转动惯量对柔性水翼弯曲振动频率影响不显著，极少出现频率锁定现象；α和转动惯量对扭转响应具有较大影响，小α下水翼几乎不发生扭转，相对较高的扭转运动均发生在α>20°时，且扭转振动频率随折减速度增加而增大；水翼的弯曲振动主要为简谐振动，随折减速度增加和α降低转变为非谐混沌运动。（4）发现近壁面水翼弯曲扭转振动频率锁定区间明显大于无壁面的柔性水翼，且弯曲扭转振幅也更大；在频率锁定区间内，小攻角下的近壁面柔性水翼升阻比会随折减速度大幅度增加；中等攻角下的近壁面柔性水翼升阻比会随折减速度先增加后减小；大攻角的近壁面柔性水翼升阻比随折减速度增加缓慢下降。研究结果对丰富和发展流固耦合动力学理论及柔性结构振动控制利用方法具有非常重要的学术意义，为水力机械及船舶动力装备的设计和运行提供理论依据和技术基础。