Investigation on the Effects of Stiffness Model on the Fatigue Damage of the Moorings for a Wave Energy Converter

The present study investigates the effects of the dynamic stiffness model on the fatigue damage assessments in the moorings of a synthetic, three-leg moored wave energy converter using fully coupled numerical analysis with the DNV software SIMA. The point absorber WEC prototype concept WaveEL 3.0, developed by the Swedish company Waves4Power is used in the analysis considering the environment condition of Figueira da Foz, Portugal. A taut mooring design is compared with a design including a floater at middle of each leg. The mooring tensions and dynamic response are analysed by considering quasi-static stiffness and dynamic stiffness approaches. Both the Syrope model proposed by DNV and the bi-linear model recommended by ABS are utilized for comparisons. Results show that the dynamic tensions and fatigue damage estimated by the dynamic stiffness models are significantly largen than those determined using the constant stiffness approach.