Numerical Prediction Of Aerodynamic Loads Of Wind Turbine Rotor

With the crisis of fossil fuels and various kinds of environmental problems caused by buring it,clean and renewable resources has been drawing more and more attentions.As a green and inexhaustible energy,wind power,especially wind electrcity,has got a great improvement in theory and tecnology.The exploit of wind power is gradually expanding from land to offshore,since wind increases a lot with distance on land.Because the offshore wind turibine resist the effect of wind,current and waves,its aerodynamic performance is influeced by six dimensional motion.It is vital to simulate loads acting on the wind turbine rotor,especially when the wind input is turbulent.Firstly,with the consideration of spatial conherence,accroding to harmony superposition method,the Davenport wind power spectrum based stochastic wind time series on the rotor disk of NERL 5MW floating wind turbine were simulated.After that,the target spectrum and computation spectrum were compared.The results show that this method can be applicable to simulating the turbulent wind velocity time series of a wind turbine.Secondly,based on advanced Computational Fluid Dynamics,we caculate the aerodymic loads acting on NREL 5MW wind turbine rotor by solving RANS equations.Both MRFs steady method and unsteady sliding mesh method were used to compute the moment and axial thrust acting on the rotor of a wind turbine under the uniform velocity conditions.Since official published experimetal results is not exist for NREL 5MW rotor,the validation of computatinal results were carried out by comparing with other authors? results.In paritcularly,using the turbulent wind velocity time series produced by the code developed in chapter two to define a velocity inlet,the aerodynamic perfomance of a wind turbine rotor was simulated under the fluctuating wind conditions.The curve of time series and thrust have the same tendency.Finally,the NARMAX model was applied to predict the time series of aerodynamic thrust on the rotor.The identification of NARMAX model was executed by measuring the input and output.The input of the system is the stocastic wind velocity time series,while the output is the thrust time series computed by CFD method in Chapter three.The results indicated that the NARMAX model is capable of predicting the loads acting on the rotor.NARMAX model method is as accurate as CFD method,but it is more efficient.Moreover,the nonlinear model is better than linear model in loads prediction.The results show that the method provide a new solution about loads acting on wind turbine.