Effects of Fluid forces on instability of mooring chains

Abstract

For large scale offshore floating structures such as a floating wind farm, design of a mooring system is quite important. This study focuses on a method for simulating dynamic behavior of the mooring line and system instability arising from wave inputs. In order to develop an efficient numerical model for the mooring line, this study introduces a discrete form of rotation called “the rotation update equation”. This technique approximates the rotation of the line element by using incremental components of rotation in terms of the angular velocity. As a result, this approach can bypass the parameterization of rotation in the equations of motion. On the other hand, the hydrodynamic forces acting on the lines are obtained from a modified Morison equation based on the linear potential flow theory. Then, we evaluate the system stability by changing conditions of wave inputs. Specifically, this study investigates the dynamic behavior of the mooring line subjected to the regular wave and/or the excitation from the platform motions.