Abstract: Generally, there is high-pressure oil or gas inside the ocean riser. The velocity of the fluid will greatly influence the vibration response of the riser. In this paper, the affect of fluid velocity in the riser on the natural frequency of steel catenary riser (SCR) structure is studied. The results show that the natural frequency decreases with the increase of fluid flow velocity. Thus, one should pay sufficient attention to this phenomenon in the design. Furthermore, the tensile variation of the SCR with the depth is calculated and analyzed. Considering the variation of the tension, the natural frequencies of the SCR is calculated. The influence of bending stiffness of the SCR on the natural frequency of the riser is analyzed. The results show that bending stiffness has little effect on the first 10-order frequencies. Therefore, it can be ignored in calculating the low-frequency mode vortex-induced vibration.

Key words: vibration and wave, steel catenary riser, fluid flow velocity, tension, bending stiffness, natural frequency

摘要： 海洋立管内部一般有高压的油或气通过，这将对立管的振动响应产生较大的影响。首先研究SCR管内流体的流速对结构固有频率的影响，结果表明：立管的固有频率随着管内流体流动速度的增加而降低，应在设计时予以足够重视。另外又分析悬链线立管张力随水深的变化规律，计算考虑变张力的立管固有频率，比较分析弯曲刚度对固有频率的影响。结果表明：弯曲刚度对前10阶频率影响不大。因此，在计算低模态的涡激振动时，可以忽略弯曲刚度的影响。

关键词: 振动与波, 钢悬链线立管, 流体流速, 张力, 弯曲刚度, 固有频率