Abstract The structural fatigue damage caused by vortex-induced vibration (VIV) is one of the most important failure reasons for flexible cylinders in offshore engineering applications. Helical strakes are often employed to reduce the VIV of slender marine structures. Based on a previous experimental investigation, this paper further investigates the effects of the yaw angle on the VIV fatigue damage of a yawed flexible cylinder with or without helical strakes in a uniform flow. Four yaw angles (α= 0°, 15°, 30° and 45°) are considered. The rain-flow counting (RFC) procedure and the Miner-Palmgren hypothesis are adopted to calculate the fatigue damage of the flexible cylinder. The influence of the yaw angle on the strain response, fatigue damage distribution and maximum fatigue damage of the flexible cylinder are investigated and discussed. The fatigue damage levels in the cross-flow (CF) and in-line (IL) directions of the flexible cylinder are obviously reduced by helical strakes. The VIV fatigue damage of the smooth cylinder is nearly independent of the yaw angle, while that of the straked cylinder is extremely sensitive to the yaw angle. As the yaw angle increases from 0° to 45°, the fatigue damage of the straked cylinder caused by VIV increases several orders of magnitude.

中文翻译：

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偏航角对有无螺旋列偏航圆柱体VIV疲劳损伤的影响

摘要 涡激振动（VIV）引起的结构疲劳损伤是海洋工程应用中柔性圆柱体最重要的失效原因之一。通常采用螺旋列板来降低细长海洋结构的 VIV。本文在之前的实验研究的基础上，进一步研究了偏航角对均匀流动中带有或不带有螺旋列板的偏航柔性圆柱体的 VIV 疲劳损伤的影响。考虑了四个偏航角（α= 0°、15°、30° 和 45°）。采用雨流计数（RFC）程序和Miner-Palmgren假设来计算柔性圆柱体的疲劳损伤。研究和讨论了偏航角对柔性圆柱体应变响应、疲劳损伤分布和最大疲劳损伤的影响。螺旋列板明显降低了挠性圆柱体横流（CF）和同轴（IL）方向的疲劳损伤水平。光滑圆柱体的 VIV 疲劳损伤几乎与偏航角无关，而条纹圆柱体的 VIV 疲劳损伤对偏航角极为敏感。随着偏航角从 0° 增加到 45°，VIV 引起的列式气缸疲劳损伤增加了几个数量级。