Dynamic Analysis Of Deepwater Steel Catenary Riser

The oil and gas resources are very abundant in the south sea of our country, but most in thedeep water, while our oil exploitation is mainly in shallow water, and the technology isrelatively behind other countries, so the research of deepwater technology is imminent. SteelCatenary Riser is the first choice of riser system which is indispensable in deepwaterdevelopment. It and marine cable systems both belong to ocean engineering structures of longand thin, whose geometric nonlinearity is very significant.This paper uses Lumped mass method to study dynamic response characteristics of steelcatenary riser. The method is widely used in dynamic analysis of ocean cable systems, in thepast few decades, which has been greatly improved and whose calculate results are accurateenough. At present most works establish their models mostly based on local coordinate system,and then transform the local coordinate system to inertial coordinate system by coordinatetransformation, so that some singularity points must be removed in the process of calculation. Inthis paper the derivation of calculation equations for various forces acting on the SCR is in theinertial system. And the three dimensional lumped mass model is obtained by Newton’s SecondLaw at last, which could avoid tedious coordinate transformation and singularity. At the sametime, the model is transformed to the matrix form for programming convenience. In order toreduce amount of calculation and save time of solution, we use the adaptive step runge-kuttamethod to solve equations. We also give three different forms of catenary equation for the initialvalue of calculation. So we could choose different forms of catenary equation according to thegiven initial conditions.At the end of the paper, we write dynamic analysis program for steel catenary riser basedon the above theoretical results by MATLAB. First, three numerical examples are presented toverify the exactness and effectiveness of the program, and then the program is used to analyzethe dynamic characteristics of simple steel catenary riser by changing the direction of current,the physical characteristics of internal flow and the motion of offshore platform. Based on theabove analysis we found that the direction of current, the density of the internal flow have a biginfluence on the internal tension and bending moment, and the riser with large displacementmotion to adapt to the movement of offshore platform.