Numerical Analysis of Turbulent Inflow Characteristics on Aerodynamic Loads of HAWT Rotor

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This project is aimed at the development of numerical methods to simulate a turbulent wind field and to predict its influence on aerodynamic loads experienced by a HAWT rotor.The turbulent wind field simulation generates time series of turbulent wind speed at several points in a rotor plane for use in the aerodynamic loads analysis, taking account of the correlation of the wind time series at a certain point with that at every other point. The wind field simulation model is constructed on the basis of a Fourier synthesis method (the Veer's model). In this model, the required inputs are the power spectrum densities (PSDs) and the coherence functions of the turbulent wind, which define the cross spectral densities (CSDs) between any two points in the rotor plane. The vector of complex Fourier coefficients of the simulated wind can be determined by adding random phases to the set of PSDs and CSDs. By performing an inverse Fourier transform of the vector, the time series of the wind is obtained.For the calculation of aerodynamic loads on the rotor blades, an inviscid aerodynamic model based on an asymptotic acceleration potential method is adopted. This calculation model can easily evaluate the effects of the flow unsteadiness in the rotor plane induced by the wake. Unsteady aerodynamic loads caused by the dynamic stall effects are taken into account by using the ONERA method.It is analyzed how the aerodynamic loads on the rotor (ex.flapping moment) respond to turbulence characteristics of the wind incoming to the rotor. Turbulence characteristics of the wind incoming to a turbine rotor bring about complicated aerodynamic loads on the wind turbine, which must be considered in the structural design process of the rotor blades. The present calculation model has a possibility to develop a simple design tool.