Abstract Helical strakes are widely used to suppress vortex-induced vibration (VIV) in offshore engineering. However, the VIV response and suppression efficiency of the straked pipe remain unclear in an oscillatory flow. In this paper, an experimental study of VIV for a flexible pipe fitted with helical strakes was conducted in an oscillatory flow with the Keulegan-Carpenter (KC) number varying from 21 to 165 and maximum reduced velocities ranging from 4 to 12. The effects of the helical strakes on the VIV response, Strouhal number, suppression efficiency and fatigue damage in an oscillatory flow were investigated. The results show that the suppression efficiency and fatigue damage reduction ratio are not as ideal in oscillatory flow as those in steady flow. Moreover, the VIV dominant frequency is obviously magnified and a large Strouhal number is observed, reaching 0.439 under a lower reduced velocity of 4. As the reduced velocity further increases to 6, 8, 12, two branches of Strouhal numbers are clearly seen. The dominant frequency decreases at the first branch with a small KC number and increases at the second branch with a large KC number.

中文翻译：

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振荡流中装有螺旋列板的挠性管的涡激振动

摘要 螺旋列板在海洋工程中被广泛用于抑制涡激振动（VIV）。然而，在振荡流中，条纹管的 VIV 响应和抑制效率仍不清楚。在本文中，在 Keulegan-Carpenter (KC) 数从 21 到 165 不等、最大折减速度从 4 到 12 不等的振荡流中，对装有螺旋列板的挠性管的 VIV 进行了实验研究。研究了振动流中 VIV 响应的螺旋列、斯特劳哈尔数、抑制效率和疲劳损伤。结果表明，振荡流中的抑制效率和疲劳损伤减少率不如稳态流中的理想。而且，VIV 主频明显放大，观察到较大的 Strouhal 数，在较低的折算速度 4 下达到 0.439。随着折算速度进一步增加到 6、8、12，可以清楚地看到 Strouhal 数的两个分支。主频率在 KC 数较小的第一个分支处降低，在 KC 数较大的第二个分支处增加。