Development of rational design methodology of deep sea riser

编制了深海立管数值模拟程序，对有限差分方法和有限元模拟方法进行了研究，采用了有限元方法。隔水管主体分为多个段。局部弯曲和扭转由假定为刚性的相邻线段的相对位移表示。然而，假设每一段都响应于拉伸和压缩而伸展和压缩。我们从写在每一段的欧拉角中的系统的拉格朗日函数推导出一段系统的运动方程。假定相对流动发生在与管片圆柱体轴线垂直的平面内，并且没有部件进入管片圆筒轴线，计算管片上的水动力、附加质量和阻力，通过将模拟的运动、张力和弯矩与实验测量结果进行比较，验证了计算机程序的有效性。在立管悬吊条件下，利用自行开发的计算机程序设计了一套深海立管，并对其在波浪中漂浮的受力情况进行了试验。

We completed a computer code to numerically simulate the behaviors of deep sea riser.Both finite difference and finite element modeling have been studied for the code ; the latter was employed. Riser body is divided into numerous segments. Local bending and torsion are represented by the relative displacement of neighboring segments which are assumed rigid. Nevertheless each segment is assumed to extend and compress responding to tension and compression.We derive the equation of motion of a system of the segments from Lagrangean function of a system written in the Euler angle of each segment. Hydrodynamic forces on the segments, added mass and drag force, are computed assuming that the relative flow occurs in the plane normal to the axis of the segment cylinder and has no component into the axis.Our computer code was validated by comparing the simulated motion, tension and bending moment, with the measured ones obtained in the experiments. The experiment are with the hang-off condition of a riser and the forced motion given by the supporting platform floating in waves.We designed a deep sea riser by using the computer code we developed.