Study on Unsteady Aero-dynamic Load Analysis of Horizontal Axis Wind Turbine Rotor

复杂的地形已成为WTGS（风力发电系统）选址的吸引力。然而，复杂地形上的气流湍流强度要比平坦地形上的湍流强度大得多，这会增加风力机叶片的气动载荷。因此，正确估计和/或测量复杂地形上的风的湍流特性对WTGS和风力涡轮机叶片的设计非常重要。通过数值计算研究非定常流场对叶片负荷波动的影响也是必要的。在本研究中，进行了以下三个项目。采用基于面板法的数值计算方法，分析了在非定常流动条件下，HAWT动叶的局部迎角。采用偏航入流条件进行计算，发现当偏航失调角较小（5 ~ 15°）时，迎角沿展向分布呈正弦波波动；当偏航失调角增大到30°时，由于动态失速效应，迎角波动呈现高频分量。2003年11月19日至2004年3月23日，在日本爱知县下原町利用多风杆进行了详细的风测。通过分析平均风速的垂直剖面和湍流的功率谱、相干性等特征，探讨了地形坡度对风的影响。水平轴风力机系统中塔架的存在对周围流体流动有较大影响。在逆风风力机中，当风力机叶片经过塔前时，会产生非定常气动载荷。本研究还试图建立一种计算塔存在对气动载荷影响的数值方法。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，该模型能够计算非定常气动载荷。在模型中，旋翼叶片用展向和弦向压力分布表示。为了使数值模型与叶片气动载荷的计算相适应，用压力分布来表示塔体。少

Complex terrain has become attractive as the site proposed for WTGS(Wind Turbine Generator System). The turbulent intensity of the wind flow over the complex terrain is, however, much larger than that over flat terrain, and it brings about increased aerodynamic load on the wind turbine blades. Therefore it is important for the design of WTGS and wind turbine blades to estimate and/or to measure the turbulent characteristics of the wind over complex terrain correctly. It is also necessary to examine the effects of the unsteady flow conditions on the blade load fluctuation by means of a numerical calculation. In the present research, the following three projects have been performed.A local angle of attack to HAWT rotor blade has been analyzed in the unsteady flow conditions, by means of numerical calculation based on the panel method. Yawed inflow condition was adopted for the calculation, and the spanwise distribution of the angle of attack (A.O.A.) is found to fluctuate in sinusoidal m … More anner when the yaw misalignment angle is small as much as 5〜15 deg. When the misalignment angle is increased to 30 degree, the fluctuation of A.O.A.shows high frequency component because of the dynamic stall effects.The detailed wind measurements using multi wind-masts were also carried out at Shitara-Cho, Aichi in Japan during the period from November 19th in 2003 to March 23rd in 2004. The influence of the terrain slope on the wind has been examined by analyzing the vertical profile of mean velocity and the characteristics of the turbulence, such as the power spectrum and the coherence.The existence of tower in horizontal axis wind turbine system has a large effect on surrounding fluid flow. In case of upwind wind turbines, the unsteady aerodynamic loads occur when the blades of a wind turbine are passing in front of the tower. The present research has also tried to produce a numerical method for calculating the effect of tower existence on the aerodynamic loads. For the calculation of aerodynamic loads on the rotor blades, an inviscid aerodynamic model based on the asymptotic acceleration potential method was adopted, which is capable of calculating the unsteady aerodynamic loads. In the model, the rotor blades are represented by spanwise and chordwise pressure distributions. The tower is represented by pressure distribution, in order to adapt the numerical model to that for the calculation of aerodynamic loads on the blades. Less