本研究利用粒子影像測速法（Particle Image Velocimetry, PIV）探討不同葉片配置之小型水平軸風力機近尾流流場特性，並比較二葉與三葉風機在葉片正面與反面安裝條件下之尾流渦流結構與紊流行為差異。風力機運轉時會於下游形成速度缺損區、剪切層與葉尖渦（tip vortex）等複雜流動結構，這些尾流特徵將影響風能擷取效率與下游流場穩定性，因此近尾流流場分析對於風力機設計具有重要意義。
本研究建立四種葉片配置案例，包括三葉正面安裝、三葉反面安裝、二葉正面安裝與二葉反面安裝，並於相同轉速條件下進行風洞實驗，以降低轉速差異對尾流特性的影響。實驗中利用垂直雷射光片與 PIV 系統量測風機後方近尾流速度場，並透過影像交互相關運算取得瞬時速度向量。進一步計算平均速度場、速度缺損、紊流強度、Reynolds stress 與渦量分布，以分析不同葉片配置對尾流結構與動量傳輸之影響。
研究結果顯示，不同葉片數與葉片安裝方向會明顯改變近尾流流場結構。三葉風機因葉片分布較密集，其尾流速度缺損區域較連續，葉尖渦排列亦較均勻；相較之下，二葉風機尾流則呈現較強的週期性與局部速度波動。另一方面，葉片反面安裝可能造成氣動性能下降，使尾流區域出現較強速度缺損與紊流擾動。本研究結果可作為小型水平軸風力機葉片設計與尾流特性分析之參考。

This study employs Particle Image Velocimetry (PIV) to investigate the near-wake flow characteristics of small-scale horizontal-axis wind turbines with different blade configurations. The wake vortical structures and turbulence behaviors of two-bladed and three-bladed rotors are compared under front-side and reverse-side blade installation conditions. During wind turbine operation, complex flow structures, such as velocity-deficit regions, shear layers, and tip vortices, are formed downstream of the rotor. These wake characteristics affect wind-energy extraction efficiency and the stability of the downstream flow field. Therefore, the analysis of near-wake flow structures is of considerable importance for wind turbine design.
In this study, four blade-configuration cases are established, including a three-bladed rotor with front-side installation, a three-bladed rotor with reverse-side installation, a two-bladed rotor with front-side installation, and a two-bladed rotor with reverse-side installation. Wind tunnel experiments are conducted under the same rotational-speed condition to reduce the influence of rotational-speed variation on the wake characteristics. During the experiments, a vertical laser light sheet and a PIV system are used to measure the near-wake velocity field behind the wind turbine. Instantaneous velocity vectors are obtained through image cross-correlation processing. The mean velocity field, velocity deficit, turbulence intensity, Reynolds stress, and vorticity distribution are further calculated to analyze the effects of different blade configurations on wake structures and momentum transport.
The results show that blade number and blade installation direction significantly influence the near-wake flow structure. Owing to the denser blade arrangement, the three-bladed rotor produces a more continuous velocity-deficit region and a more uniform tip-vortex distribution. In contrast, the wake of the two-bladed rotor exhibits stronger periodicity and more pronounced local velocity fluctuations. In addition, reverse-side blade installation may reduce aerodynamic performance, leading to stronger velocity deficits and turbulence disturbances in the wake region. The results of this study can serve as a useful reference for blade design and wake-flow analysis of small-scale horizontal-axis wind turbines.

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