剪切流作用下立管涡激响应的研究

Research on Vortex-Induced Vibration in linearly sheared flow

为研究剪切流作用下立管的涡激振动问题,文章建立了三维立管的涡激动力响应方程,顺流方向的力通过Morison方程求解;横向涡激力采用改进的尾流阵子模型求解,考虑了附加质量的变化;轴向力的计算考虑平台升沉运动的影响。采用有限单元法离散控制方程,离散后的方程采用Newmark-β法在时域求解。在此基础上,研究了剪切流作用下立管的多模态涡激振动响应,讨论了剪切参数对立管涡激动力响应的影响,并比较了均匀流和剪切流条件下立管不同的响应特征。结果表明,剪切参数对立管的涡激响应动力响应有很大的影响,剪切流条件下立管呈现的多模态响应极为复杂,与均匀来流条件下的振幅和频率响应特点明显不同。

In order to solve the problem on Vortex-Induced Vibration of marine riser at sheared flow, three dimensional governing equations are given. The in-line force is solved by Morison equation while crossflow force is solved by wake oscillator model which takes the movement of platform and variation of added mass into consideration. The governing equations are discretized by finite element method and solved by Newmark-β method in time domain. Based on this model,this paper discussed multi-mode excitation of riser pipeline in linearly sheared flow, the effect of shear parameter on vortex induced vibration and dynamic response of riser pipeline, and compared the different responses in uniform and linearly sheared currents. The results indicate that the shear parameter has a significant effect on vortex induced vibration and dynamic response of riser pipeline. The multi-mode response of riser pipeline in linearly sheared flow differs from that in uniform current.