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涡激振动是诱发海洋管道与浮式平台系泊缆线等细长柔性圆柱结构疲劳损伤的重要因素,已有研究大多关注结构轴向与来流垂直的情况,实际的海洋工程中,圆柱结构轴向与来流并不完全垂直,存在一定倾斜角度。针对这种复杂的情况,倾斜圆柱涡激振动的不相关原则被提出,即假定倾斜圆柱涡激振动与来流速度在结构轴向的垂直方向投影分量引起的垂直圆柱情况等价。然而,较大倾角条件下不相关原则的正确与否仍未知。为了论证大倾角倾斜柔性圆柱涡激振动不相关原则,开展了长径比为350,倾角为45°的倾斜柔性圆柱涡激振动实验,采用应变传感器测量结构应变信息,运用模态分析法对实验数据进行处理。通过大倾角倾斜圆柱与垂直圆柱的实验结果对比,发现在控制模态转化区域,倾斜圆柱更容易被激发高阶模态,同时倾斜圆柱与垂直圆柱在测点处的应变和位移差异较大,并均出现高频特征。最终得出了较大倾角状态下倾斜柔性圆柱涡激振动不相关原则不成立的结论。
Vortex-induced vibration is an important factor inducing the fatigue damage of elongated flexible cylindrical structures such as marine pipelines and floating platform mooring cables. Most of the studies have been focused on the vertical structure of the axial flow and the incoming flow. In actual offshore engineering, the cylindrical structure Axial and incoming flow is not completely vertical, there is a certain tilt angle. In view of this complicated situation, the irrelevant principle of inclined cylinder vortex is proposed. That is, it is assumed that the inclined cylinder vortex is equivalent to the case of a vertical cylinder caused by the vertical component of the flow velocity in the axial direction of the structure. However, the correctness of the principle of irrelevance under the conditions of greater dip is still unknown. In order to demonstrate the irrelevant principle of vortex-induced vibration of flexible cylinder with large dip angle, a vortex-induced vibration experiment of inclined flexible cylinder with an aspect ratio of 350 and a dip angle of 45 ° was carried out. Strain sensors were used to measure the structural strain information. Modal analysis Data processing. By comparing the experimental results of steep columns and vertical columns with large dip angle, it is found that inclined columns are more likely to be excited higher modes in the controlled modal transformation region, while the differences of strain and displacement between inclined and vertical columns are larger at measuring points High-frequency features appear. Finally, the conclusion that the irrelevant principle of vortex-induced vibration of inclined flexible cylinder under the condition of large inclination is not established.