基于FBG传感技术的立管涡激振动过程分析
Analysis on Process of Vortex induced Vibration of Risers Based on FBG Sensing Technology

为深入研究光纤光栅传感技术在海洋立管涡激振动测试中的适用性，在风-浪-流联合水槽中进行均匀来流下立管涡激振动试验。数据测试采用光纤光栅传感器，同时采用动态电阻传感器作为对比。通过改变多级外流流速，对比分析基于两种传感技术的立管涡激振动过程差异。同时基于光纤光栅传感技术采集应变数据并结合频谱分析及模态理论，研究立管振动的主导频率、幅值及模态响应等振动特性。研究结果表明，光纤光栅传感技术对海洋立管的涡激振动测试性能优越，能够准确体现立管的应变时程、振幅以及主导频率等振动特性，清晰反映伴随流速进程的立管模态特征及涡激振动过程，同时由模态响应和涡激振动过程分析发现立管锁频区间的产生具有瞬时性及自激性规律，这对海洋立管的模型试验与工程设计具有较大的参考价值。
To further investigate the applicability of fiber Bragg grating (FBG)sensors sensing technology for testing of vortex induced vibration(VIV) of deep sea risers, this paper describes laboratory tests of VIV of a model deep sea riser in a uniform current, which were carried out in a wind wave current flume. The riser model, 1.5m long and with a slenderness ratio of 83.33, was tested in conditions in which the upper 0.75　m was in air, while the lower 0.75m was exposed to a uniform current. FBG sensors were used for data acquisition and dynamic strain sensors were used for comparison. By changing the external flow velocity, the difference of the VIV process of the riser attained by two different sensors was analyzed and the vibration performance of the riser such as dominant frequency, amplitude and modal response based on frequency analysis and modal theory were researched implemented. The results indicate that requirement of FBG technology for testing of VIV of deep-sea risers can be wonderful satisfied. The vibration performance of the riser is accurately demonstrated. Modal characteristics and VIV process of the riser accompanying external flow velocity process are clearly reflected. The instantaneity and learly.