Motions and mooring loads of a tanker moored at open jetty in long crested irregular waves including second order effects
The motions of a moored vessel and the loads on the mooring lines and fenders are evaluated in frequency domain in an accurate and simple way. The linearized stiffness matrix for the mooring system including pre-tension and coupling is calculated using an existing numerical code based on the differential linearization. A Green’s function panel method is used for the hydrodynamic calculations. The second order calculations are performed with an approximate method where the second order velocity potential is calculated without considering the forcing function on the free surface boundary condition. Results for the motions and mooring forces in long crested irregular waves are compared with experimental data available in the literature for a loaded 200 kDWT tanker, moored to an open jetty in water with a depth amounting to 1.2 times the draft of the vessel. The results show a good agreement with the experimental data and show that the second order low frequency loads should not be neglected when calculating the loads on the mooring lines and fenders in irregular waves.