细长柔性立管涡激振动疲劳损伤分析

Fatigue Damage Analysis of Vortex-Induced Vibration of a Long,Flexible Riser

为了深入分析细长柔性立管涡激振动响应带来的疲劳损伤,在拖曳水池中对柔性立管进行了试验研究.由拖车带动立管运动产生相对来流,再根据测试得到的应变数据,结合材料常数得到立管的疲劳损伤.分别使用了基于单频率、常幅值的频域法以及多频率、变幅值的雨流法对疲劳损伤进行分析.分析发现:不同流速、相同模态阶数下的应变响应频率很接近,是由不同的流速在立管周围产生不同的流体附加质量所致.在大多数情况下,频域法得到的预测疲劳损伤比雨流法得到的真实疲劳损伤要大;但在少数情况下则相反.

In order to further analyze the fatigue damage induced by vortex-induced vibration（VIV）of a flexible riser,laboratory tests were conducted on a flexible riser in a towing tank.The relative current was simulated by towing the riser in one direction.Based on the measured strain,the fatigue damage was obtained combined with the material parameters.The frequency domain method based on the single-mode frequency and constant amplitude strain,and the rainflow method based on the multi-mode frequency and varied amplitude strain were both applied on the riser.The analysis results indicate that the values of frequency components in the same order under different velocities were relatively close,but not exactly the same,which was caused by the fact that the different velocity would induce different added mass around the riser.For most cases,the predicted fatigue damage by using the frequency domain method is larger than the measured value by using the rainflow method.However,for some cases,the measured fatigue damage is larger than the predicted fatigue damage.Thus,it should be very careful to use the frequency domain method for the predictions of VIV fatigue damage on a long,flexible riser.