Investigation of the VIMs of a spar-type FOWT using a model test method

Abstract

This article presents the research findings of an extensive model test investigation of the dynamic response to vortex-induced motions (VIMs) of the OC3 spar-type floating offshore wind turbine (FOWT). Particulars of this research are to investigate the unique and crucial effects of wind load on the spar-type FOWT, which differs considerably from other traditional spar-type floating systems utilized in the gas and oil industry, on the VIMs. The model test was performed with a sequence of current, wind and irregular wave sea states to analyze the nature of the coupled dynamic response behavior of VIMs. Many unique characteristics were found and analyzed. The lock-in phenomenon of sway in the cross flow (CF) direction was found to occur first, followed by the lock-in phenomenon of surge in the in-line (IL) direction. For the current-only case, the remaining responses, including the other 4-degree-of-freedom (DOF) motions, mooring tensions and turbine bearing loads, were found to be coupled by sway/surge VIMs. Moreover, the oscillation amplitudes of all of the responses increased significantly with increasing current velocity, particularly after locking-in. Furthermore, the wind load had a clear suppression effect on the CF and IL VIM responses. The experimental measurements demonstrated that the wave load excites wave-induced oscillations for some CF responses and all IL responses, and it further restrains the VIM oscillation amplitudes on the foundation of the wind suppression effect. In particular, when a wind load is involved, the influence of current or wave is limited to the yaw and IL tower-top bending moment.

Influence of Clumps-Weighted Moorings on a Spar Buoy Offshore Wind Turbine

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Numerical Analysis of a Catenary Mooring System Attached by Clump Masses for Improving the Wave-Resistance Ability of a Spar Buoy-Type Floating Offshore Wind Turbine

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“…The model test has been accepted as a reliable approach to study the performances of offshore floating wind turbines. Duan et al (2016) launched a model test program to investigate the vortex induced motion of a spar-type floating wind turbine. Li et al (2018b) measured the dynamic response of a semisubmersible floating wind turbine in experimental environment, and a free-rotation method was proposed to correct the Reynolds number dissimilitude.…”