The vortex-induced vibration and solid-structure impact of a neutrally buoyant horizontal flexible pipe in the vicinity of a bottom wall boundary are experimentally investigated in a water flume. The pipe with an aspect ratio of 87 is arranged with an oblique angle of 30° and an initial gap-to-diameter ratio of 0.5. A non-intrusive measurement with two high-speed cameras is employed to simultaneously capture the spatial-temporal vibration displacements in both inline and crossflow directions, and the pipe-wall impact process in the reduced normal velocity range of 3.40–14.43 with a maximum Reynolds number of 2780. Experimental results highlight the new pipe equilibrium profiles deviating away from the bottom boundary due to the wall proximity and wall collision. The occurrence of wall-impact is determined by whether the crossflow amplitude is larger or equal to the summation of the new equilibrium position and initial gap. The observed five distinct solid-pipe impact patterns as well as the location and length of the impacting segments are closely associated with the dominant response mode and the space-varying response amplitude. Particularly, the response mode competition contributes to the spatial shift of impacting position over time.

中文翻译：

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底壁边界附近涡激振荡柔性管道的固体结构冲击模式

在水槽中实验研究了底壁边界附近的中性浮力水平柔性管的涡激振动和固体结构冲击。纵横比为87的管道以30°的斜角和0.5的初始间隙直径比排列。使用两个高速摄像机进行非侵入式测量，同时捕获在线和横流方向的时空振动位移，以及在 3.40-14.43 的降低法向速度范围内，最大雷诺数下的管壁冲击过程数量为 2780。实验结果突出显示了新的管道平衡轮廓由于壁面接近和壁面碰撞而偏离底部边界。壁面冲击的发生取决于横流幅值是否大于或等于新的平衡位置和初始间隙的总和。观察到的五种不同的实心管撞击模式以及撞击段的位置和长度与主要响应模式和空间变化响应幅度密切相关。特别是，响应模式竞争有助于影响位置随时间的空间转移。