Comparative Study of Lifting Operations of Offshore Wind Turbine Monopile and Jacket Substructures Considering Vessel Shielding Effects

Abstract

In this paper, the shielding effects from an installation vessel during lifting operations are investigated. The study compared the lifting operations of two commonly used offshore wind turbine substructures: the monopile and the jacket substructure. The fluid characteristics near the vessel are firstly studied in the frequency-domain. The numerical model of the coupled lifting system is established and eigenvalue analysis is carried out. The shielding effects from the floating installation vessel during the lifting operation are accounted for by interpolating wave kinematics between pre-defined wave points near the vessel in the time-domain simulations. The responses of the monopile and the jacket considering shielding effects are compared with those assuming wave kinematics due to incident waves only. The results indicate that a great reduction in the responses can be achieved when the shielding effects are considered during lowering the monopile, while the effects are very limited when installing the jacket foundation. The effects on the monopile and the jacket are compared and discussed in detail.