剪切流下钢悬链线立管涡激振动响应研究

Prediction of vortex-induced vibration of a SCR under shear current

给出线性轴向张力下顶端张紧式立管忽略弯曲刚度时的固有频率和模态振型解析解,与Shear7给出的结果进行比较。结果表明:在低于20阶模态数时,两种方法得到的固有频率能很好地符合;在高于20阶模态数时,随模态数的增加,两种方法得到的固有频率结果差距也逐渐变大,因此弯曲刚度不能忽略。由悬链线方程将钢悬链线立管等效为顶端张紧立管,通过研究顶端张紧式立管的涡激振动响应来研究钢悬链线立管的涡激振动响应。研究发现钢悬链线立管的静态位移与转化之后的等效立管均方根位移组成了类似于锯条的形状。

An analytical solution was presented for a vertical linearly tensioned riser without flexural rigidity.In the case of less than 20 modes,natural frequencies and modal shapes of the analytical solution were in agree with those of Shear7 program.In the case of more than 20 modes,the difference of the two methods increased with mode number,so flexural rigidity could't be neglected.An equivalent vertical straight riser was defined to have approximate parameters of SCR a with catenary equation.The VIV response of the SCR was obtained through predicting the VIV response of the equivalent riser with Shear7 program.It was found that the shape of the SCR's static displacement combining with that of the equivalent riser's RMS displacement looks like a saw blade.