Experimental Investigation of VIM Characteristics on Column Type Floater in Super Critical Reynolds Number

In Japan, floating wind turbine facilities are 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 application is that the facilities are mounted on a column type floater to keep buoyancy and stability in the sea that is called as Spar type. At that time, the characteristic of VIM, i.e. Vortex Induced Motion, on the column type floater is concerned about to maintain mooring safety of the wind turbine. VIM characteristic on the column type floater was investigated using a huge experimental model in supper critical Reynolds number at the large towing tank in the National Maritime Research Institute, Japan. The results of the experiment were compared with ones of a small similar figure model under critical Reynolds number, and VIM amplitudes against reduced velocity parameter are clearly understood. The amplitude distribution relating to duration time for large VIM amplitude is also investigated to assess the effect on fatigue damage of mooring lines. These unique and precious results have important role for making the safety guideline on mooring requirement on a column type floater.