Abstract Flexible cylinder structures, such as top-tensioned risers (TTRs) and tethers of tension leg platforms (TLPs), display complicated dynamic characteristics under the combined excitation of vortex-induced vibration (VIV) and time-varying axial tension, which causes serious fatigue damage and is a major concern in ocean engineering fields. In this paper, model tests were conducted on a flexible cylinder with an aspect ratio of 350 and a mass ratio of 1.90 to study the effect of time-varying tension on the VIV response. Three tension amplitude ratios (Tv/Tc = 0.1, 0.2 and 0.3, where T v is the amplitude of the varying tension and Tc is the constant tension) and six tension frequency ratios (fv/f1 = 0.5, 1.0, 1.5, 2.0, 3.0 and 4.0, where f v is the frequency of the varying tension and f1 is the 1st-order natural structural frequency) were considered. The Reynolds number ranged from approximately 800 to 16,000. The displacements were reconstructed with the measured strains using a model analysis method. The effects of the tension amplitude ratio and tension frequency ratio on the dynamic characteristics were discussed from the maximum root mean square (RMS) of the displacements, power spectral density (PSD) plots, time-space-varying displacements, and motion trajectories. The tension excitation places the vibration into a higher-order mode earlier. For a large tension amplitude ratio (Tv/Tc = 0.3), the max RMS of the cross-flow (CF) displacement remarkably increases because the frequency of the varying tension is equal to the parametric resonance frequency (fv/f1 = 2.0). The effect of the tension frequency ratio is enhanced with the increase in the amplitude ratio. For the case of fv/f1 = 2.0, the sum and difference frequencies disappear, and the bandwidth of the dominant frequency widens. Figures in the shape of the number 8 are not found in the motion trajectory plots for Tv/Tc = 0.3, indicating that energy transfer is influenced by tension excitation. The in-line (IL) vibrations show an alternate conversion between the 5th-order mode vibrations and the analogous 3rd-order mode vibrations.

中文翻译：

---

伴随涡激振动和时变轴向张力激发的细长柔性圆柱体的动力学特性

摘要 顶张立管（TTRs）和张力腿平台（TLPs）系绳等柔性圆柱结构在涡激振动（VIV）和时变轴向拉力的联合激励下表现出复杂的动态特性，导致严重疲劳损伤是海洋工程领域的一个主要问题。本文在纵横比为350、质量比为1.90的柔性圆柱体上进行模型试验，研究时变张力对VIV响应的影响。三个张力幅度比（Tv/Tc = 0.1、0.2 和 0.3，其中 T v 是变化张力的幅度，Tc 是恒定张力）和六个张力频率比（fv/f1 = 0.5、1.0、1.5、2.0、 3.0 和 4.0，其中 fv 是变化张力的频率，f1 是一阶自然结构频率）被考虑在内。雷诺数的范围从大约 800 到 16,000。使用模型分析方法用测量的应变重建位移。从位移的最大均方根（RMS）、功率谱密度（PSD）图、时空变位移和运动轨迹等方面讨论了拉伸幅度比和拉伸频率比对动态特性的影响。张力激励使振动更早地进入高阶模式。对于大的张力振幅比 (Tv/Tc = 0.3)，横流 (CF) 位移的最大 RMS 显着增加，因为变化的张力的频率等于参数共振频率 (fv/f1 = 2.0)。张力频率比的影响随着幅值比的增加而增强。对于 fv/f1 = 2.0 的情况，和频和差频消失，主频带宽变宽。在 Tv/Tc = 0.3 的运动轨迹图中找不到数字 8 形状的数字，表明能量传递受张力激励的影响。在线 (IL) 振动显示了 5 阶模式振动和类似的 3 阶模式振动之间的交替转换。表明能量传递受张力激发的影响。在线 (IL) 振动显示了 5 阶模式振动和类似的 3 阶模式振动之间的交替转换。表明能量传递受张力激发的影响。在线 (IL) 振动显示了 5 阶模式振动和类似的 3 阶模式振动之间的交替转换。