本研究使用數值方法計算在額定風速與額定轉速的運轉狀態下，2MW水平軸風力發電機之風機氣動力特性。本研究利用求解不可壓縮流場之連續方程式、動量方程式以及紊流模型以獲得風機周圍流場。本研究首先討論計算空間尺寸對風機流場與氣動力特性的影響，以決定風機流場計算所需的適當空間尺寸；接著討論流場入口位置之紊流強度對風機流場與氣動力特性的影響，以了解紊流強度與風機流場變化的相關性；最後討論流場入口位置之冪次律風速分布對風機流場與氣動力特性的影響，以了解風速分布與風機氣動力特性的相關性。本研究使用的計算區塊主要可分為兩大區塊，分別為包含風機葉片的轉動區塊以及其外部的流場區塊。本研究計算結果顯示，當計算空間入口位置與風機距離2倍轉子直徑，計算空間高度及寬度大於1.5倍轉子直徑以及計算空間出口位置與風機距離6倍轉子直徑時，風機的氣動力特性趨於定值，此時該值與計算空間幾何尺寸大小無關。改變入口位置之紊流強度，對於風機周圍流場與氣動力特性無顯著影響。增大入口位置風速分布的指數值會降低風機輸出功率大小。當指數值由0.1增大為0.5時，風機輸出功率則會減少5%。

This study investigates the aerodynamic characteristic of a 2MW horizontal-axis wind turbine at the rated wind velocity and rated rotational speed via a numerical approach. The flow field around a single wind turbine is obtained by solving the continuity and momentum equations incorporated with a turbulence model, where an incompressible flow field is assumed. First, the influence of the size of computational domain on the flow field around a single wind turbine and its aerodynamic characteristics is studied to determine the adequate size of computational domain in the numerical simulation. Second, the effect of turbulence intensity at the flow inlet on the flow field around a single wind turbine and its aerodynamic characteristics is examined to disclose the dependence of flow characteristics on turbulence intensity. Finally, the flow field around a single wind turbine and its aerodynamic characteristics are calculated for different wind profiles specified at the flow inlet to reveal the correlation between the aerodynamic characteristics and the shape of wind profile. Two mesh blocks are employed in this study, where the rotating one to describe the rotor blades is embedded inside the stationary one defining the size of computational domain. The numerical results indicate that the aerodynamic characteristics become independent on the size of computational domain provided that the distance between the wind turbine and flow inlet is larger than two times of the rotor diameter, the distance between the wind turbine and the flow outlet is greater than six times of the rotor diameter, and the height and width of computational domain are not less than one and half of the rotor diameter. The variation of turbulence intensity at flow inlet yields very limited impact on the flow field and aerodynamic characteristics of wind turbine. The increase of the exponent of the wind profile at flow inlet leads to the decline of delivered power, where the growth of exponent from 0.1 to 0.5 results in a power reduction of 5%.

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