海洋立管涡激振动的高倍谐振特性及其影响研究

Vortex-induced vibration (VIV) of marine risers is one of the frontier subjects in ocean engineering. However, the mechanism and effects of higher harmonics of vortex-induced vibration have not been known well. Both model tests and numerical simulations will be conducted in this work. Through analyzing existing experimental data, we will find the basic factors which affecting high harmonics of VIV of marine risers. With experimental tests, the mechanism and characteristics of the high harmonics of VIV will be revealed. Laser displacement sensors, particle image velocimetry (PIV) and strain and acceleration sensors will be combined to improve the accuracy of structural motion and vortex field measurement. Fast multipole method (FMM) will be used in order to improve the efficiency of the calculation of the vortex-induced velocity and reduce the work of numerical calculation. Radial basis function (RBF) will be applied to improve the accuracy of the calculation on vorticity diffusion by spatial correction. Then, coupled with the strip method, a quasi-3D DVM model will be established in order to predict the VIV of long flexible cylinders by combining the 2D DVM model with the finite element method (FEM) structure model. Then, numerical simulations of flow induced vibration of long flexible cylinders will be conducted. The simulation results will be compared with the experimental results to show whether the present DVM model could be reasonably used to predict the VIV of long flexible cylinders. Higher harmonics of the VIV response such as the third, fourth and fifth harmonics frequencies will be shown. Components of the high harmonics of VIV will be obtained by using wavelet analysis and modal analysis. By rainflow counting method, fatigue damage of the high harmonics of VIV will be obtained to find the effects of the high harmonics of the VIV including both in the in-line direction and cross-flow direction. The results of this work will be put forward for the optimization of the suppression method of VIV of marine risers.

海洋立管涡激振动是海洋工程领域的前沿课题，目前对海洋立管涡激振动高倍谐的机理特性及其影响尚不深入。为此，本项目拟从模型实验和数值模拟两个方面开展研究。分析已有相关实验数据，找到影响高倍谐振的基本要素，开展实验验证，进而揭示高倍谐振的产生机理和特性；应用激光位移传感器、粒子图像测速技术（PIV）与应变和加速度传感器相结合，提高立管运动与涡流形态的量测精度；应用多极子展开法计算流场中离散涡元涡诱导速度，减小计算量和存储量，采用径向基函数对涡核扩散进行空间修正，提高涡量扩散计算的准确性；采用切片理论，结合有限元结构模型，建立柔性立管涡激振动的准三维数值CFD模型；采用小波分析分离高倍谐振中的多个频率信号，应用模态分析法和雨流法计算分析运动响应特性和导致的疲劳损伤，提出高倍谐振在立管涡激振动中的影响范围和程度，包括横流向和顺流向两个方向的影响，为立管抑振方法和抑振措施的改进和提高提供理论依据。

海洋立管涡激振动是海洋工程领域的前沿课题，本项目从模型实验和数值模拟两个方面对海洋立管涡激振动高倍谐的机理特性及其影响开展研究。分析相关实验数据和文献资料，对影响高倍谐振的参数进行分析，开展模型实验，分析高倍谐振的产生机理和特性；应用模态分析和双侧传感器数据分析方法对涡激振动进行观测，提高了量测精度；应用多极子展开法计算流场中离散涡元涡诱导速度，减小计算量和存储量，采用径向基函数提高涡量扩散计算的准确性；采用切片理论，结合有限元结构模型，建立柔性立管涡激振动的准三维数值CFD模型；采用小波分析分离高倍谐振中的多个频率信号，应用模态分析法和雨流法计算分析运动响应特性和导致的疲劳损伤，提出高倍谐振在立管涡激振动中的影响范围和程度，包括横流向和顺流向两个方向的影响，为立管抑振方法和抑振措施的改进和提高提供理论依据。在本基金项目的支持下，研究成果发表5篇学术论文，其中3篇发表到China Ocean Engineering等SCI检索期刊，培养研究生3名。