冲蚀地形上悬跨海底管线涡激振动试验研究

Experimental Investigation for Vortex Induced Vibration of Submarine Pipeline Suspended Over a Trench

为了给海底管线服役期间的安全评估提供科学依据,基于水弹性相似关系,对海底管线服役期间常见水流环境条件下,冲蚀地形上悬跨弹性海底管线涡激振动进行试验研究。采用粘贴于管线内壁的应变片测量振动过程中的应变。通过与平底地形上相关研究结果进行对比分析发现:冲蚀地形上悬跨海底管线涡激振动强度与振动频率均受到冲蚀地形的影响;振动强度随水流折减速度的变化比平底地形要快,在相对冲坑长(悬跨长)L/D为20与L/D为35时涡激振动强度的差别较平底地形上悬跨管线要小得多;管线垂向振动频率随冲蚀地形冲坑长度的减少而增大;冲蚀地形上悬跨管线周围的斯特劳哈尔数St在0.21左右,比相同雷诺数下平底地形上悬跨管线周围St数略大。

To provide scientific evidence for safe assessment of submarine pipelines in common marine environments for submarine pipelines in service,following the requirements of the hydroelastic similitude criteria,the experiments were conducted on vortex induced vibration of flexible submarine pipelines suspended over a trench.Strain was measured via strain gauges bonded on the inner surface of the pipeline.The results were analyzed by comparing with those of vortex induced vibration of submarine pipeline over a flat seabed.It reveals that the trench exerts an effect on vortex-induced vibration intensity and frequency of flexible submarine pipelines suspended over a trench.The variation of vortex-induced vibration intensity of suspended pipeline over a trench with current reduced velocities is faster than over a flat seabed.The difference of vortex-induced vibration intensity of suspended pipeline over a trench between relative trench length(span length) L/D=20 and L/D=35 is small comparing with those of vortex-induced vibration of submarine pipeline over a flat seabed.The vibration frequency of submarine pipeline in the transverse direction increases with the decrease of the ratio of trench length.Moreover,Strouhal number of vortex shedding frequency of suspended pipeline over a trench gets near 0.21,a little greater than that of suspended pipeline over a flat seabed.