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Flow-induce motions (FIM) small-scale model tests were performed for the Jappaku floating offshore wind turbines (JPK), a FOWT developed to operate in Brazilian waters. This paper aims to investigate the presence of FIM on the JPK to show the importance of heave plate (HP) design and to show how HP mitigates FIM. Three different HP dimensions were tested and compared with the condition without HP. In addition, two different incidence angles of the current were tested, namely, 0 deg and 180 deg. The results showed amplitudes in the transverse direction similar to the diameter of the external platform column for the case without HP. These amplitudes are higher than the ones observed for previous deep-draft semi-submersibles found in the literature. Conversely, the largest HP dimensions implied in mitigation of the FIM amplitudes, i.e., very low amplitudes, were observed. The presence of the central column played an essential role in FIM and significantly modified the amplitudes in different current incidences. Due to the different diameters of the external and central columns, the FIM presented two different branches of response related to the vortex-shedding frequency around the columns. The results showed that significant FIM could occur for this specific JPK investigation even with HP. The HP design has a positive effect on reducing dynamic behaviors due to the wave and current incidences. Therefore, its design must be included in the preliminary stages of FOWT developments. [ABSTRACT FROM AUTHOR]

Flow-induced motions (FIM) are an issue for floating offshore structures, such as multi-column platforms, as the phenomenon can decrease the fatigue life of the mooring, riser, and cable systems. The new concept of floating offshore wind turbines (FOWT) have a multi-column design that may be subjected to FIM. In the past, FIM was studied mainly for Oil & Gas platforms installed in deep waters. However, the FIM phenomenon of FOWT has been insufficiently explored. To rectify this, model tests were performed for the semisubmersible (SS) floating system design developed for the DeepCwind project (Offshore Code Comparison Collaboration Continuation (OC4) phase II). This paper will investigate the presence of FIM and show its importance in the design process of FOWT. Three different incidence angles of the current were tested, namely, 0, 90, and 180 deg. For each heading, 30 reduced velocities were tested, across the range 8000 < Re < 70,000. The results showed amplitudes in the transverse direction of around 70% of the diameter of the platform column, which is similar to those observed for deep-draft (DD) SS with circular columns. Note that these amplitude values are larger for a floater with a circular column, than for a platform with square columns. The results showed that as FIM occurred for this specific FOWT SS, its effect has to be considered in the mooring system and electric cable design. [ABSTRACT FROM AUTHOR]