Numerical Simulation of a Polyester Mooring System Interacting with a Classical SPAR

A numerical scheme, known as CABLE3D, originally developed for the simulation of dynamics of steel mooring lines is extended to allow for special properties pertaining to polyester ropes, such as relatively large elongation under tension, dependence of the modulus on loads and energy dissipation under cyclic loads. The modified CABLE3D is then integrated into a numerical package, known as COUPLE, for computing the interaction between a floating structure and its polyester mooring system. A classical SPAR is chosen in this study as a representative of deepwater floating structures. By considering large elongation in polyester ropes, the static offset curve of a polyester mooring system is found to be softer than that calculated under the assumption of small elongation. The effects of the mean loads on the modulus of polyester ropes are much greater than those of the dynamic loads. The energy dissipation in polyester ropes under cyclic loading does not play a significant role in the responses of the SPAR and tensions in a polyester mooring system. The above observations though made based on a classical SPAR may still have important implications to other floating structures moored by a polyester mooring system.