Simultaneous Wake- and Vortex-Induced Vibrations of a Cylinder With Two Degrees of Freedom in Each Direction
Simultaneous Wake- and Vortex-Induced Vibrations of a Cylinder With Two Degrees of Freedom in Each Direction
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DOI：
10.1115/1.4027523
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发表时间：
2014-08
影响因子：
1.6
通讯作者：
J. Chaplin;W. Batten
中科院分区：
文献类型：
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作者：
J. Chaplin;W. Batten
一个圆柱体在另一个圆柱体尾随流动引起的振动是与深水中垂直张力立管之间的相互作用有关的持续关注的主题。当一个立管位于另一立管下游时，它可能会同时受到不同频率的尾流引起和涡流引起的激励。两者都是复杂的机制，可以合理地假设它们相互作用。为了开始理解这个复杂的过程，任何建模都应该包含多自由度结构响应的一些特征。为此，本文描述了一些实验，在这些实验中，一个圆柱体在稳定流动中，在一个类似但静止的圆柱体下游自由地同时承受尾流和涡流引起的振动。下游气缸安装在弹性系统上，该系统在顺流和横流方向上都有两个固有频率。所有四种模式中的质量比几乎相同。对沿直线方向 5 和 10 直径以及横向最多 4 直径的气缸间隔同时进行的尾流和涡流引起的振动进行了测量。在 83 的降低速度（基于圆柱体较低的水下固有频率）和 5 个直径的间隔下，当下游圆柱体靠近上游圆柱体尾流的边缘时，尾流引起的振动偏移在几乎 5 个直径处达到峰值
The flow-induced vibration of one cylinder in the wake of another is the subject of continuing interest in connection with interactions between vertical tension risers in deep water. When one riser is downstream of another it is likely to be subject to wake-induced and vortex-induced excitations at different frequencies simultaneously. Both are complex mechanisms, and it is reasonable to assume that they interact. To begin to understand this complicated process it is desirable that any modelling should incorporate some features of a multi-degree-of-freedom structural response. With this aim, this paper describes experiments in which one cylinder was free to undergo simultaneous wake- and vortex-induced vibrations downstream of a similar but stationary cylinder in a steady flow. The downstream cylinder was mounted on an elastic system that had two natural frequencies in both the in-line and cross-flow directions. Mass ratios were almost the same in all four modes. Measurements are presented of simultaneous wake- and vortex-induced vibrations for cylinder separations of 5 and 10 diameters in the in-line direction, and up to 4 diameters transversely. At a reduced velocity of 83 (based on the cylinder’s lower submerged natural frequency) and a separation of 5 diameters, excursions of wake-induced vibrations peaked at almost 5 diameters, when the downstream cylinder was near the edge of the upstream cylinder’s wake