Mooring Systems – A Multibody Dynamic Approach

A method for simulating the motion behaviour of moored floatingoffshore structures in the time domain is presented. Theinteraction between the fluid and the floating structure isconsidered using linear potential theory. The hydrodynamic forcesacting on the mooring lines are computed using a modified Morisonequation. A complete three-dimensional model of the structure andthe mooring lines is generated using a multibody system approachincluding a subsystem technique. The model results in a largenumber of degrees of freedom. In order to illustrate a practicalapplication of this method, an analysis of a moored ponton in arandom sea is presented. Different configurations of the systemare examined in order to evaluate the motion behaviour and therestoring forces. Comparisons are made with the naturalfrequencies of the damped system.