DYNAMIC ANALYSIS OF MOORING CABLE FASTENING A FLOATING SPHERE ON THE OCEAN

摘要

Mooring cable system, fastening the floating platform is an indispensable segment in the development and utilization of ocean energy. However, the nonlinear cable geometry and nonlinear hydrodynamic forces perplex the construction of numerical modelling of mooring cable. Traditionally, the cable modelling is constructed just considering the geometry of cable, the normal, and the tangential directions. Not only the geometry of cable, but also the relative velocity of fluid is involved in constructing of the numerical modelling of cable in this paper. The expression of external loads by this numerical modelling is effective and accurate taking advantage of explicit separation of external loads in transverse and lengthwise directions. This modelling also simplified the formulation of hydrodynamic drag forces which is dominant among external loads. The stiffness and damping of cable, apparent weight, hydrodynamic drag forces, effect of added mass, and Froude-Krylov force are considered during building of this numerical modelling. The mooring cable fastening a floating sphere stands on buoyancy forces due to the submerged sphere. The simulation results of this numerical modelling were compared and verified with the results from Pro-teusDS which is an offshore simulation code.