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Note: MOPS

Abstract: As a consequence of the planned exit from fossil-based energy in the European Union the exploitation of renewable energies has become a major aspect of the Offshore Industry. Especially the construction and operation of offshore wind energy turbines pose a challenge which is met by the use of jack-up vessels with extendible legs. In order to dimension the vessel´s manoeuvring devices in the early design stage and to ensure a safe jackup process for given environmental loads the dynamic positioning capability during the jacking including the influence of the legs has to be calculated. As part of the development of a holistic dynamic analysis this paper presents the implementation of the leg´ influence in an existing manoeuvring method. The manoeuvring method solves the equations of motion in three degrees of freedom (surge, sway, yaw). It is based on a force model which comprises various modular components. Therefore another component for the leg-forces is added. A Morison approach is chosen to calculate the hydrodynamic forces on the cylindrical legs. The legs´ hydrodynamic added masses are accounted for and added to the hull´s inertial terms. The benefit of the presented method is the possibility to calculate the dynamic positioning capability with extended legs without being dependent on the results of either time-consuming or non-specific model tests. Therefore the method represents a fast computing tool to design the vessel for the specific environmental conditions of the site of operation.