Coupled Analysis Of Novel Concept Of Floating Offshore Wind Turbine Under The Combined Wind And Wave Conditions

Renwable energy has received keen interest in a sustaninable future given to the factor that it plays an important role for reducing greenhouse gas emission,and thus in mitigating climate change.The development of renenwable energy can help to change energy consumption mixture,reduce the environment pollution and promote to sustainable economic and society development.Many government in the world have introduced revelent policies to support renewabl energy development.According to the Chinese 13 th five-year plan(FYP)of renewable energies,the total installed capacity of renewable energies in China will reach 1.9 trillion k Wh by 2020,the total electricity generation from renewable energy will grow up to 27% of the total electricity.As one of the promising renewable energy,wind energy will grow up to 6% of the total electricity.With the running out of onland area for onshore wind tubine,offshore wind is becoming more popular.China has vast of ocean areas.Thus,there is a huge potential to deploy offshore wind farm with abundant wind resoures.Depending on water depth,offshore wind turbines can be installed in shallow water or deep water.In deep water,floating offshore wind turbine shows a great economic feasibility.In this paper,the coupled analysis is carried out to investigate the dynamic response of novel V-shaped semisubmersible FOWT under combined wind and wave conditions.The main contents of this paper are given as follows:(1)Frequency domain analysis of a V-shaped semi-submersible floating platform.Referring to the concept design of the V-shaped semi-submersible floating offshore wind turbine,the hydrodynamic model of the platform is established in WAFDUT.The added mass,radiation damping and first-order wave force of V-shaped semi-submersible floating platform are calculated to reveal the influence of the geometry of the structure on the hydrodynamic properties of the platform.The response amplitude operator(RAO)of the V-shaped semisubmersible floating platform is calculated to reveal the capacity of structure’s motion to the wave load resistance.(2)Motion responses analysis of the V-shaped semi-submersible FOWT under the combined wind and wave conditions.The coupled numerical model of V-shaped semisubmersible FOWT is established in FAST.The hydrodynamic loads are calculated using the Morrison equation and first-order potential flow theory.The high-order boundary element method(Ho BEM)is used to calculate the hydrodynamic force of V-shaped semi-submersible floating platform in WAFDUT.The natural frequency is calculated by free-decay test simulation for V-shaped semi-submersible FOWT i;the numerical simulation of V-shaped semi-submersible FOWT is carried out using the environment conditions in South China Sea.And the motion responses of support structure,wind turbine and tower of V-shaped semisubmersible FOWT under different load conditions are discussed.(3)Dynamic responses analysis of V-shaped semi-submersible FOWT under the combined wind and wave conditions.The time-domain and frequency-domain characteristics of typical loads,such as mooring system load and tower base load,are investigated;the factors of dynamic response of typical loads under different wind and wave conditions are explored,and the V-shaped semi-submersible safety performance is evaluated.