On the seakeeping behaviour of an offshore wind farm vessel during the jack-up process in the early design stage

Abstract

Offshore wind farm vessels are oftentimes equipped with jack-up legs, to lift the hull above the water surface at the site of operation. The vessels’ harmonic motions in a seaway must be within defined limits during the initial contact of leg and seabed. This paper therefore presents the implementation of the legs’ hydrodynamic influence on the seakeeping behaviour in an existing seakeeping analysis method for application in the early design stage. It is based on a frequency domain, linear strip method providing response amplitude operators in a regular seaway. The legs’ hydrodynamic influence is included by a Morison approach. The presented method provides the possibility to quickly calculate the response motions of a jack-up vessel in a regular seaway during the jack-up process. It represents a fast computational tool for the early design stage to design the vessel especially for the environmental conditions of the site of operation.