Three-dimensional marine riser dynamics

The equations of the three dimensional motion of a marine riser undergoing large elastic deformations are formulated using Kane's formalism. The riser is modelled using lumped masses connected by extensional and rotational springs including structural damping. Surface waves are described by Stokes' second order wave theory. The hydrodynamic loads are applied via Morison's equation and added-mass coefficients using the instantaneous relative velocities and accelerations between the fluid field and the riser segments. The effect of internal flow is included in the model. The detailed algorithm is presented and the equations are solved using a robust implementation of the Runge-Kutta method provided in MATLAB. The mathematical model and associated algorithm are validated by comparing the steady state equilibrium configuration of the riser with special cases of an elastic catenary mooring line and large deflection statics of a cantilever beam. The results of sample simulations are presented.NRC publication: Ye