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

本项目旨在发展模拟湍流风场的数值方法，并预测其对HAWT转子所经历的气动载荷的影响。紊流风场模拟考虑某一点风场时间序列与其他各点风场时间序列的相关性，生成旋翼平面上若干点的紊流风速时间序列用于气动载荷分析。在傅里叶综合方法的基础上建立了风场模拟模型（Veer模型）。在该模型中，需要的输入是湍流风的功率谱密度（psd）和相干函数，它们定义了转子平面上任意两点之间的交叉谱密度（CSDs）。模拟风的复傅立叶系数矢量可以通过在psd和CSDs集合中加入随机相位来确定。通过对矢量进行傅里叶反变换，得到风的时间序列。对于旋翼叶片气动载荷的计算，采用了基于渐近加速度势法的无粘气动模型。该计算模型可以方便地评价尾迹引起的旋翼面非定常的影响。采用ONERA方法考虑了由动态失速效应引起的非定常气动载荷。分析了旋翼上的气动载荷（如扑动力矩）对进入旋翼的风的湍流特性的响应。进入风力机转子的风的湍流特性给风力机带来了复杂的气动载荷，这是在转子叶片结构设计过程中必须考虑的问题。该计算模型为开发一种简单的设计工具提供了可能。

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.