• Journal of Korean Society of Coastal and Ocean Engineers
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• v.27 no.5
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• pp.281-294
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• 2015

In order to quantitatively estimate the nonlinear destructive interaction of wave load with wind load, which is very vital for the optimal design of offshore wind energy converter, we carried out a hydraulic model test and wind tunnel test. As a substructure of offshore wind energy converter, we would deploy the monopile, which is popular due to its easiness in construction. Based on the simulation using Monte Carlo simulation using Kaimal spectrum and cross spectrum, the instantaneous maximum wind velocity is adjusted to 10 m/s. And, considering the wave conditions of the Western Sea where a pilot wind farm is planned to be constructed, $H_s=0.1m$, 0.15 m, 0.2 m is carefully chosen. It turns out that the nonlinear destructive interaction between the wind and wave loads acting on the offshore wind energy converter is more clearly visible at rough seas rather than at mild seas, which strongly support our deduction that a Large eddy, a swirling vortex developed near the bumpy water surface in the opposite direction of the wind, is the driving mechanism underlying nonlinear destructive interaction between the wind and wave loads.

• Journal of the Society of Naval Architects of Korea
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• v.52 no.1
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• pp.43-51
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• 2015

This paper presents effect of aerodynamic loads on mooring line responses of a floating offshore wind turbine. A Matlab code based on blade element momentum (BEM) theory is developed to consider aerodynamic loads acting on NREL 5MW wind turbine. The aerodynamic loads are coupled with time-domain hydrodynamic analyses using one-way interaction scheme of the wave and wind loads. A semi-submersible floating platform which is from Offshore Code Comparison Collaborative Continuation(OC4) DeepCWind platform is used with catenary mooring lines simply composed of studless chain links. Average values of mooring peak tensions obtained from aerodynamic load consideration are significantly increased compared to those from simple wind drag force consideration. Consideration of aerodynamic loads also yield larger tension ranges which can be important factor to reduce fatigue life of the mooring lines.