Dynamic Analysis Of Steel Catenary Riser Based On Absolute Node Coordinate Formulation

Deepwater steel catenary riser is an important component in offshore engineering.Its good dynamic performance plays a key role in ensuring the normal operation of deepwater oilfield development system.The absolute nodal coordinate method has wide application prospects in the nonlinear dynamics of large deformation.The establishment of the absolute nodal coordinate mechanical model for dynamic analysis of the steel catenary riser is a new and promising research area.In this paper,based on the absolute nodal coordinate formulation,considering the geometric nonlinearity of SCR,a three-dimensional analysis model for the analysis of steel catenary riser was established.And combined with finite element method,a finite element program was wrritten,and static analysis and time-domain dynamic analysis of slow-wave SCR in deep water was carried out.First,the expression of spatial configuration and structural deformation of riser is derived through continuum mechanics,and the motion balance equation of an element after deformations is derived based on the virtual work principle.Then,using a simplified three-dimension and two-node beam element,considering the coupling effect of axial deformation and bending deformation,the complete tangent stiffness matrix of the riser element,load vectors,mass matrix and boundary conditions are derived,and the program is written by Fortran language.Then,the incremental static solution algorithm and the nonlinear time-domain dynamic algorithm are applied to calculate the relevant example,which proves the correctness of the finite element program.Finally,through the analysis of slow-wave SCR,some conclusions and laws are obtained which can be provided for engineering reference,simultaneously it also shows that the analysis model is suitable for the dynamic response analysis of the deepwater SCR.This analysis model has the following characteristics: the riser element adopts elastic force and precise tangent stiffness expressions,which improves the calculation precision of the riser model;the tangent stiffness matrix of the absolute nodal coordinate formulation is a function of the absolute nodal coordinate and time,which can simulate the SCR geometric non-linearity highly effectively;using a nonlinear time-domain algorithm to solve the dynamic equations,can simulate nonlinear characteristics of hydrodynamic loads better.