本文利用大尺度渦漩模擬(LES)建立一套無需輸入翼形氣動資料，且可做出有效預測之數值模擬模型，並以此一模型對不同參數組合之垂直軸風力發電機進行流場與氣動分析。首先參考相關文獻，確立所需之網格品質(y+)後，對NACA4412之翼形進行模擬分析，結果顯示即使在失速之後，升、阻力係數與實驗之誤差皆在20%之內。之後對一直徑為0.5m、具有三片葉片之垂直軸風力發電機進行模擬，經過對支撐臂等在模擬模型中被簡化的部份進行修正後，模擬結果皆落在實驗結果的誤差範圍內，證實所建立之數值模形能有效的對垂直軸風力發電機進行模擬預測。最後以建立的數值模型對不同葉片數、半徑與Solidity之垂直軸風力發電機進行模擬，從結果可以發現半徑為0.75公尺、葉片數為二片之風力機的輸出功率係數最高，達0.354；而半徑為0.5625、葉片數為三片之風力機，在周速比為1時，輸出扭力係數為0.021，是模擬案例中啟動能力最好的。另外，從各案例間的比較發現，Solidity為影響風力機氣動特性之主因，其值愈大則啟動能力愈好，但效率愈差；反之，Solidity值愈小，效率愈高但啟動能力卻愈差。此外，葉片數對風力機的性能也有顯著的影響，葉片數較少的風力機，輸出扭力係數或輸出功率係數會比葉片數多者為佳。

This research intends to establish an accurate simulation model to execute the CFD analysis and predict the aerodynamic performance associated with a vertical axis wind turbine (VAWT). Incorporated with LES scheme, this model can perform the flow field simulation without the input of a reliable, low-Reynolds-number aerodynamic data for airfoil, which is usually not available and required for the common-used multi-streamtube model. At first, the simulation of NACA4412 airfoil is carried out to validate this new model and to decide the appropriate quality (y+) of cell. From the numerical result, even under the stall condition, the calculated lift and drag coefficients are still agree well with experimental data within 20% error percentage. Thereafter, an H-type VAWT with three blades and a 0.5m-diameter is chosen to execute the CFD simulation. The flow patterns associated with this VAWT are successfully illustrated via the numerical outcome. Also, its aerodynamic characteristics are close to the experimental result after the supporting arms of blades is taken into account in calculating the VAWT performance. In addition, a parametric study, including blade number, radius, and solidity, is carried out with the aids of this new simulation model for realizing their corresponding influences on the VAWT performance. Under all the cases considered here, it is found that the highest power coefficient ( =0.354) and torque coefficient ( =0.021) are generated by case B (R=0.75m, 2 blades) and Case D (R=0.5625, 4 blades) operating at low rotating speed (TSR=1), respectively. Moreover, the result illustrates that solidity and blade number are two dominant parameters on aerodynamic performance of VAWT. A larger torque coefficient and a smaller power coefficient are generated for the VAWT with an increasing solidity at lower rotating speed and at higher rotating speed, respectively. It implies that a lower solidity results in a higher power output and a worse starting ability for the VAWT.

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