Experimental Investigation of VIM Characteristics on Spar Type Floater in Higher Reynolds Number

FOWTs, i.e. Floating Offshore Wind Turbines, are recently planned to be set in the offshore, where bottom-mounted type's one is not feasible, to generate natural resource electricity. One of the ways for FOWTs' application is that a wind turbine facility is mounted on a slender column type floater to keep buoyancy and stability in the sea, that is called as Spartype. In this case, the characteristic of VIM, i.e. Vortex Induced Motion, on the column type floater is concerned about to keep mooringsafety of the FOWT. Then VIM characteristic on the column type floater was investigated using a huge experimental model in suppercritical Reynolds number at the large towing tank in the National Maritime Research Institute, Japan. The results of the experiment were compared with ones of small similar figure models under lower Reynolds number, and the VIM amplitudes against reduced velocity parameter were clearly understood. Using these results the amplitude distribution relating to duration time for the huge experimental model is investigated having the effect on fatigue damage of mooringlines. These unique and precious results on the column type floater have important role for safety assessment on FOWT mooringlines.