本研究旨在觀察層流場和紊流場不同攻角下表面渦流與機翼受力的變化，阻力在低攻角時主要由壁面剪應力造成，高攻角時渦流產生絕大部分的阻力，而升力主要都是由渦流產生，另外相較於紊流場，壁面剪應力在層流場情況下對升阻力有比較明顯影響。翼前緣渦流渦度通量越高代表其環流越大，而攻角越大渦度通量越大，這讓翼前緣渦流能產生更多升阻力。尾流的渦流對數和升阻力的震盪行為有關，當渦流對數只有一對時，升阻力只會有一種震盪頻率，若出現兩對時，升阻力的頻譜圖會出現低強度的雜訊。

We study the aerodynamic forces and the contributions of vorticity distribution for NACA0012 at different angles of attack. Both laminar flow and turbulent flow are investigated. At low angles of attack, the drag is mainly caused by the wall shear stress. At high angles of attack, vortices generate the majority of the drag. Lift is mainly generated by vortices. The boundary layer has a more significant influence on lift and drag in laminar flow conditions. The higher the vorticity flux into the leading-edge vortex, the greater the circulation, and the vorticity flux increases when the the angle of attack increased, which makes the leading-edge vortex generate more lift and drag. The oscillation behavior of lift and drag is related to the vortex pairs oberved in the wake. When there is only one pair of vortices each cycle, there is only one oscillation frequency for lift and drag. If there are two pairs in one cycle, the lift and drag spectrum will show low-intensity noise.

摘要 i
Abstract ii
謝辭 iii
圖目錄 vi
表目錄 viii
第一章 前言 1
第二章 方程式 13
2.1 統御方程式 13
2.2 紊流場方程式 13
2.3 力元理論11 15
2.4 史特勞數 16
第三章 數值方法 18
3.1 PISO演算法 18
3.2 Spalart-Allmaras模型12 19
3.3 k-ω SST模型13 20
3.4 兩種URANS模型比較 21
3.5離散化參數設定 22
3.6邊界條件和殘值設定 23
第四章 結果 26
4.1 網格正確性驗證 26
4.2 層流 Re=1000 31
4.2.1 機翼上表面渦流 31
4.2.2 升阻力分析 38
4.2.3 尾流與週期性動態 40
4.3 紊流 Re=100000 49
4.3.1 機翼上表面渦流 49
4.3.2 升阻力分析 54
4.4 層流場與紊流場渦流的比較 57
第五章 結論 60
參考文獻 61

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