粗糙立管涡激振动响应特性数值模拟研究

Numerical Simulation of Vortex-induced Vibration Characteristics of Rough Riser

海洋立管是连接浮式平台和海底井口的关键设备,涡激振动是其疲劳损伤的主要原因,海洋生物吸附等因素会影响立管表面的粗糙度,使涡激振动特性更加复杂。论文基于CFD(计算流体动力学)与CSD(计算结构动力学)的双向流-固耦合方法,引入粗糙壁面速度梯度修正模型,构建粗糙立管涡激振动数值计算程序,研究粗糙度、来流速度等参数对涡激振动特性的影响。研究结果表明:随着来流速度和表面粗糙度的增大,立管来流向与横流向的振动频率显著增大。较大的表面粗糙度会强化立管来流向多频和宽频振动,而较小的表面粗糙度会抑制立管来流向多频和宽频振动。随着表面粗糙度的增大,立管横流向两倍和三倍于主频率的次频减弱,多频振动特性降低,但宽频振动特征增强。

Marine riser is key equipment connecting the floating platform and the seabed wellhead,and vortex-induced vibration(VIV)is the main cause of its fatigue damage.Roughness of the marine riser surfaces is significantly affected by attached marine organisms,and makes dynamic characteristics of the riser VIV more abundant and complex.In this study,based on the bidirectional fluid–structure coupling method of CFD(computational fluid dynamics)and CSD(computational structure dynamics),a modified model of velocity gradient on the rough wall is introduced to construct numerical calculation program of VIV of a rough riser.Effects of roughness,inlet velocity and other parameters on VIV characteristics of the riser were studied,and influence of surface roughness on characteristics of the riser VIV was explored.The results show that,with the increase of the inflow velocity and surface roughness,increase of the stream-wise and transverse vibration frequency of the riser is significant.Larger surface roughness will strengthen the multi-frequency and broadband vibration of the riser,but smaller surface roughness will restrain the multi-frequency and broadband vibration.With the increase of the surface roughness,frequencies twice and three times of the main frequency of the riser in the transverse direction decrease,and multi-frequency vibration characteristics decrease,but broadband vibration characteristics will increase.