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为研究输运不同流体的海洋立管在海流作用下的振动规律,在大型波浪流水槽中进行涡激振动模型实验。实验分别将四种不同质量比的立管模型竖直固定于支架上,立管外部承受不同速度的流体作用,上端施加顶张力。立管模型上均匀布置六个测点,根据每个测点布置的两个应变计,分别测得来流向和横向两个方向振动响应。通过小波变换对实验数据进行去噪处理,利用振型分解法求解立管各点涡激振动位移。考察输运不同流体对立管自振频率以及涡激振动响应的影响,并利用雨流计数法对模型进行疲劳分析。实验结果表明,随质量比增加立管涡激振动频率降低;低质量比的立管更容易产生大位移。
In order to study the vibration law of marine risers transporting different fluids under ocean currents, a vortex-induced vibration model experiment was carried out in a large wave-flow water tank. Four vertical riser models with different mass ratios were vertically fixed on the support. The riser was subjected to fluid with different velocities on the outside and top tension on the top. Six measuring points are evenly arranged on the riser model. According to the two strain gauges arranged at each measuring point, the vibration responses in the two directions of flow direction and lateral direction are respectively measured. The experimental data are denoised by wavelet transform, and the vibration mode displacement method is used to solve the vortex-induced vibration displacement at each point of the riser. The influence of different fluids on the natural frequency and the vortex-induced vibration response of risers was investigated. The fatigue analysis of the model was made by rain-flow counting method. The experimental results show that the vortex frequency of riser decreases with the increase of mass ratio, and the riser with low mass ratio is more prone to large displacement.