平台运动影响下张力腿涡激振动特性研究

张力腿涡激振动易引起系泊系统的疲劳损伤，危害张力腿平台的安全性和可靠性。该文借鉴细长立管涡激振动的相关研究，同时考虑张力腿与立管在截面尺度、预张力大小以及边界条件存在的巨大差距，采用切片理论结合CFD数值模拟方法，对平台运动影响下张力腿涡激振动开展了研究。考虑定常张力与时变张力对涡激振动的影响，采用GAMBIT软件分区建立了多切片计算网格，将编制求解涡激振动的UDF程序嵌入Fluent软件中，采用动网格技术实现流场的更新并计算作用于张力腿上的瞬时升力和拖曳力。文中还比较了仅考虑流和考虑浪、流联合作用张力腿的时变张力影响，研究了两种典型波高共计六种工况，计算结果表明：随着流速的增加，各模态权重比例将发生跳转现象；尽管由于平台运动导致张力腿受力的随机性，但平台运动对张力腿涡激振动影响较小。

Characteristics of Tendon Vortex Induced Vibrations Influenced by Platform Motion

The vortex-induced vibrations (VIVs) of tendons are associated with the fatigue damage of the mooring system. This fatigue damage endangers the security and stability of the tension-leg platform. In this paper, relevant studies on slender riser VIVs are referenced, and the substantial dif-ferences between the tendon and the riser in cross-section dimension, pre-tension, and boundary conditions are considered. Strip theory with the computational fluid dynamics numerical simulation method is employed to study the VIV of tendons influenced by the platform motion. Given that VIVs are affected by time-varying tensions, GAMBIT software is used to set a multi-slice computational grid and UDF programs are embedded into Fluent software to solve the VIVs. The instantaneous drag and lift forces on the tendon can be calculated because the flow field is updated with dynamic mesh technology. And then the influences of the time-varying tension of the tendon are compared only in current or in a combination of current and waves. A total of six working conditions that contain two types of typical wave heights are studied. Computation results show that the ‘jump’ phenomenon oc-curs in the weight proportion of each mode with decreasing velocity. Although platform motion caus-es the forces acting on the tendon to become stochastic, the VIVs of the tendon are less affected by such motion.