Analysis of Lifting Operation of a Monopile Considering Vessel Shielding Effects in Short-crested Waves

This paper addresses numerical simulations of the lifting operation of an offshore wind turbine monopile foundation, considering both the shielding effects of the vessel and the spreading of the waves. A numerical model of the coupled monopile-vessel system is established. The disturbed wave field near the vessel is investigated and observed to be affected by the diffraction and radiation of the vessel. The shielding effects of the vessel during the lifting operation are accounted for in this study by interpolating the fluid kinematics between predefined wave points near the vessel using MARINTEK SIMO software and an external Dynamic Link Library (DLL). The effects of short-crested waves on the wave field and on the responses of the system are investigated by implementing the directional spreading function in the wave spectrum. On the basis of the time-domain simulations, the critical responses of the lifting system in various conditions are studied. The results indicate that the effects of the wave spreading are considerable in both incident and disturbed waves. The shielding effects are less significant in short-crested waves than in long-crested waves