垂直軸風力機葉片的非定常空氣動力特性由複雜的流體行為所主導，造成此動態氣動力特性的原因，主要來自隨著旋轉角度變化的相對攻角、速度向量和雷諾數，而這些動態效應將導致垂直軸風力機無法自行啟動，這項缺點仍待克服。
本研究實際量測Darrieus風力機的功率輸出和Giromill風力機提供的扭力，功率量測結果用於驗證Matlab所撰寫的多流管模型(Double Multiple Streamtubes Model)模型，再應用此多流管模型預測各風速下垂直軸風力機的啟動扭力，動態失速的影響則使用修正過的Gormont模型來校正，扭力量測結果用於討論低風速下垂直軸風力機提供的Reaction Torque和Rotary Torque對啟動能力的影響，接著參考Oler的實驗結果驗證商業計算流體力學(Computational Fluid Dynamics)套裝軟體計算模擬的可靠度，最後再針對本研究之Giromill風力機進行模擬，討論尖端速度比為1及2下，葉片附近的二維無因次渦量場，此外也使用相位平均(phase-locked average)計算出各旋轉角度葉片提供的平均切線推力來判斷產生負扭力的區域，並分析各葉片之切線推力對淨值貢獻的大小。

The main objective is to analysis the self starting problem. This research investigated the torque and power generation of the vertical axis wind turbine (VAWT) using experimental and numerical method. The VAWT has an inherent unsteady aerodynamic behavior due to the variance of angle of attack angle with the angle of rotation, perceived velocity and consequentially Reynolds Number. The phenomenon of dynamic stall has a significant impact on VAWT in the starting ability and torque output at the low tip speed ratio.
The experimental method was developed to measures the reaction torque and rotary torque varying with angle of rotation. Moreover, A numerical method, the Double-Multiple Streamtube (DMS) model was employed to predict the torque coefficient by five levels wind speed. Furthermore, in order to clearly visualize the development of the flow field of the airfoil, efforts were carried out with Computational Fluid Dynamics (CFD). The flow configuration of a 2D model was created to represent the three bladed VAWT with infinite aspect ratio. The phase-locked average of tangential force shows the negative regimes. The pressure and vorticity fields shows the evolution of the tangential force with the vortex shedding.

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