海洋立管复模态动力特性分析

Dynamic Characteristics Analysis of Marine Risers by Complex Mode

考虑阻尼的影响,研究海洋立管的动力特性。通过分析管内流体及管外海洋环境荷载的共同作用,建立海洋立管涡激振动偏微分方程,进而得到立管动力特性方程,用复模态分析法求解动力特性方程得到立管考虑阻尼的自振频率。算例计算表明:考虑阻尼的立管自振频率略小于不考虑阻尼的立管自振频率;立管的自振频率随着内流流速的增加而减小,但内流流速不大时,影响较小;管道长度对立管的自振频率影响较大。

The effect of the damping term is taken into account in the analysis of dynamic characteristics in this paper. Based on Francis Biolley＇s wake oscillator model developed from the classical van der Pol equation, the differential equation for the response of the vortex-induced vibration （VIV.） of the riser considering the effect of the internal flowing fluid and the external marine environmental condition is derived. Then solved the characteristics equation by the complex mode method to obtain the natural frequencies of the risers with damping. The results indicate that the natural frequencies with the damping are smaller than those without damping, and the first mode frequency decreases with the increase of internal flow velocity. But the effect on the frequency is not obvious when the internal flow velocity is slow; and the effect of the riser span is more obvious.