并列双立管涡激振动特性的数值和实验研究

摘要

In order to research the wake and force in vortex-induced vibration ( VIV) , Ansys-CFX and model test are used for the VIV of single riser and the two risers in 2~8D spacing.Fluid-structure interaction is considered in the CFX.It is shown that, the lift force of the two risers comes to maximum in 3D spacing, the phase difference of drag force is 0°and lift force is 180°in this case, and a variable velocity field with a frequency the same as vortex shedding is generated in the overlapped area which leads to the period of drag force the same as that of lift force.It can be concluded that the interaction between the two par-allel risers is significant when the risers are brought to a small distance for the trajectory of riser changes from oval to curve 8 as the spacing is increased.So when installing the riser, the distance should be around 8D spacing.%为了观察并列双立管涡激振动中尾流及升阻力的变化情况，采用CFX数值模拟和实验相结合的方法对单立管及中心间距为2～8倍直径的并列双立管进行研究，CFX计算时考虑流固耦合的作用。结果表明：在间距为3倍立管直径时升力幅值出现最大值，此时两立管拖曳力一致，升力相位差为180°，且此时尾流叠加区域产生了一个与涡泄频率一致的速度变化场，导致立管的拖曳力周期与升力周期相同；随着间距的增加，一侧立管运动轨迹从椭圆形向8字形转变，可见低倍立管间距时，立管间的相互作用明显，随着距离的增大，影响将逐渐减弱。因此立管设计安装时中心距离应远离3倍直径，最好在8倍直径附近比较安全。