空化流动载荷作用下弹性水翼结构稳定性研究

The structural stability is the key issue for the safe operation of the hydraulic machinery and marine engineering equipment. As the most severe operation conditions, the cavitating flow is characterized by the obvious nonlinearity of the load, strong interaction between the fluid and structure, a wide frequency domain of the exciting force and strong transient impact on the structure. To improve the structural stability of the elastic hydrofoil in cavitating flows, the relation between the unsteady cavitation development and the added hydrodynamic forces will be built, based on the experimental and numerical method, to establish the hybrid-coupled fluid-structure interaction algorithm with added cavitation hydrodynamic effect considered. The data correction and analysis technique will be explored for the postprocessing of the experimental data obtained from the Partical Image Velocimetry, which is applied to the cavitating flow around a deformable wall boundary. Based on that, the refined measurement and analysis of the unsteady cavitating flow structures around an elastic structure can be realized. In order to address the scientific issues, including the evolution of cavitating flow patterns around elastic hydrofoils and the unstable mode of cavitating flow induced vibrations, the experimental and numerical investigation for the evolution of the cavitating flow structures around elastic hydrofoils will be conducted. Combined the physical and numerical studies, the structural stabilities under cavitating flow dynamics and hydroelastic responses will be studied, and the corresponding structural stability boundary will be revealed. Thus will offer theoretical and methodological support to the development and safe operation of the hydraulic equipment.

结构稳定性是涉及水力机械与海洋工程装备安全运行的核心关键问题。以强非线性和强流固耦合为特征的空化载荷由于具有激励频域宽和局部瞬态强冲击等特性，是装备最为严苛的运行环境。申请者针对空化条件下弹性水翼结构的稳定性问题，基于已有的实验和计算基础，构建非定常空化流场中空穴形态演变与结构附加水动力载荷的表征关系，建立考虑空化瞬态附加水动力载荷的混合耦合数值计算方法；突破弹性壁面边界的粒子图像测速数据修正与分析技术，建立弹性边界非定常空化流场结构测试与分析方法。围绕绕弹性水翼空化流动的流型演变规律和空化载荷作用下弹性水翼结构振动的不稳定模式等科学问题，开展绕弹性水翼壁面空化流动结构演化的试验和数值计算工作，研究弹性水翼在非定常空化载荷作用下的结构稳定性，揭示弹性结构对非定常空化载荷的响应机制，获得弹性水翼结构的稳定性边界，为水力机械装备研制和运行安全提供理论和方法支撑。

本项目采用实验与数值模拟相结合的方法，针对空化流动载荷作用下弹性水翼结构稳定性开展了系统研究。主要研究工作及创新性成果如下：.基于多场同步试验平台，发展了基于图像的结构尖端小变形测量方法，突破了激光粒子图像测速技术在弹性壁面边界的数据修正与分析技术，发展了变形边界复杂空化流场结构测试与分析方法；开展了不同流动条件下的空化试验研究，获得了绕弹性水翼空化流型图，为弹性壁面边界绕流空化水动力学数值研究提供了重要实验依据。.基于实验数据模化分析，获得了绕弹性水翼不同空化阶段空泡形态、水动力特性和空化流激振动的响应特性，综合考虑多相复杂流场边界层流动分离与转捩特性、空化模型和结构水弹性响应特性的表达，构建了非定常空化流场中空穴形态演变与结构附加水动力载荷的表征关系，建立了考虑空化瞬态附加水动力载荷的混合耦合计算模型。.综合运用试验测量与数值计算，获得了弹性水翼在非定常空化载荷作用下回射流机制和冲击波机制诱导的结构动态响应特性，分析了水弹性响应对不同脱落机制空化载荷的影响。结果表明，弹性水翼由于扭转变形促进空化增长，相比于不锈钢水翼降低了大尺度云状空泡团脱落频率，增大了升力系数和力矩系数。基于对弹性水翼振动速度的分析，揭示了弹性水翼在空化载荷作用下的振动响应频谱特性。振动响应的主频对应空泡脱落频率，表明空化载荷主导结构振动。进一步分析了弹性水翼在非定常空化载荷作用下的静态发散、动态发散、颤振等不稳定模式，获得了空化载荷作用下弹性水翼结构的发散边界。基于本征正交分解方法，分析了水弹性响应对不同尺度空泡结构能量分布的影响，结果显示大尺度云状空泡团结构的能量最高，对应流场的主要相干结构；基于动力学模态分解方法，获得了弹性水翼主要失稳频率及其对应的流场结构。