The Motion Response Analysis Of Offshore Floating Wind Turbine System On Waves

With the increasing shortage of fossil fuels and environmental contamination,adjusting the energy structure has become a top priority around the world.As a kind of safe,clean and abundant renewable energy,wind energy has become the focus of the development of renewable energy.At present,the main utilization of wind energy is generating power.While wind turbines on land occupy much land resources and have many other disadvantages,offshore wind energy becomes the trend of development.Considering the restrictions on coastline utilization in the near-shore region as well as the rich reserves of wind energy in deep-water area,offshore wind power develops towards deep sea.The cost of fixed wind turbine will increase dramatically when the water depth exceeds 60 meters.However,floating wind turbine could solve this problem efficiently.The main types of offshore floating wind turbine are TLP type,Spar type and semi-submersible type.Floating wind turbine system consists of wind turbine,floating platform and mooring system.The system bears aerodynamic force,wave force and mooring force during operation.Meanwhile,the sea conditions in deep sea are rather harsh,it is necessary to conduct coupled analysis to avoid instability or overturned.Coupled analysis could consider the interaction between different parts of the system and predict the motion response more precisely.It can also provide references for the design of wind turbine and mooring system.This paper establishes a time domain coupled calculation method for the motion response of floating wind turbine system,including aerodynamic module,hydrodynamic module and mooring system module.The CFD method is used in aerodynamic module to calculate wind force,and then the wind force model is established by NARMAX theory.The free surface Green's function method based on potential flow theory is used in hydrodynamic module to calculate the hydrodynamic parameters in frequency domain,then the results are transformed into time domain.The non-linear 3-dimensional finite element method based on anchoring line theory is used in mooring module to analyze the mooring system.The motion equation is solved by Newmark-? method.Then the coupled analysis of a Spar-type floating wind turbine system is conducted in several working conditions.The results include the wind force NARMAX model,hydrodynamic parameters,motion and tension response.This coupled calculation model would be helpful in the designing process of the floating wind turbine platform and mooring system.