Mooring systems - A multibody dynamic approach

A method for simulating the motion behaviour of moored floating offshore structures in the time domain is presented. The interaction between the fluid and the floating structure is considered using linear potential theory. The hydrodynamic forces acting on the mooring lines are computed using a modified Morison equation. A complete three-dimensional model of the structure and the mooring lines is generated using a multibody system approach including a subsystem technique. The model results in a large number of degrees of freedom. In order to illustrate a practical application of this method, an analysis of a moored ponton in a random sea is presented. Different configurations of the system are examined in order to evaluate the motion behaviour and the restoring forces. Comparisons are made with the natural frequencies of the damped system.