Parametric Study of Mooring Lines on a Small Buoy

A shallow-draft cylindrical buoy and mooring lines comprise an integrated dynamic system responding to environmental loading due to wind, current and waves in a complex way. In this paper, a time-domain decoupled buoy motion analysis method will be applied to study numerically the effect of the length, pre-tension and coordinates of attached points of the mooring lines on the motions of the buoy and the loads of the mooring lines. The wind and the current speeds are assumed to be constant and the wind and current forces are estimated from empirical formulations. The hydrodynamic coefficients, wave exciting forces and slow drift forces of the buoy are obtained from the 3D diffraction-radiation theory. The numerical results show how the length of the mooring line influences the maximum mooring loads at severe sea. The results also quantitatively show how the pre-tension and the coordinates of attached point of the mooring lines affect the motions and loads of the moored system.