動態失速為一複雜之流體動力現象，伴隨著層流分離氣泡(laminar separation bubble，LSB)、前端渦旋(leading edge vortex，LEV)、二次渦旋的產生以及渦旋剝離。本研究主要目的是在探討與分析流體流過擺動機翼所產生的動態失速現象，採用RANS(Reynolds-average Navier-Stokes)之SST k-ω紊流模型以及Transition SST紊流模型，並運用動網格技術模擬不同實驗，結果以正向力係數對攻角作圖呈現，並和現有實驗數據做比較，發現到在較高的雷諾數下，因為紊邊界層主導的關係，SST k-ω紊流模型的模擬結果與實驗較為相符，而Transition SST紊流模型在LEV成長以及失速的時間點皆較實驗延遲；在較低的雷諾數下，Transition SST紊流模型則較SST k-ω貼近於實驗。然而，在低無因次頻率(reduced frequency)下，兩紊流模型在失速後，正向力係數皆會產生實驗上看不到的震盪。另外，本研究藉由流線及壓力分佈分析動態失速現象並且解釋正向力係數變化的趨勢，從結果中可以發現到在低雷諾數流場下，機翼前端有較明顯的LSB產生，並且隨攻角增加而向前端收縮，最後吸引力崩解轉變成LEV，而Transition SST紊流模型因為對於有過渡現象產生的LSB掌握度較高，因此模擬結果與實驗也較為符合。

The objective of this study is to discuss and analyze the flow structure around a pitching airfoil in the flow field through simulations. The SST k-ω and Transition SST turbulence models combined with dynamic mesh are used to simulate different experiments with different reduced frequencies. The comparisons between simulations and experimental data are presented by the normal force coefficient. Furthermore, the phenomena of dynamic stalls are analyzed by the streamline and the pressure distribution. Under the higher Reynolds numbers, because of the domination of the turbulent boundary layer, the results of SST k-ω model are in good agreement with the experimental data, and the growth of leading edge vortex (LEV) and the onset of the stall postpone in the results of Transition SST model. Under the lower Reynolds numbers, laminar separation bubble (LSB) forms at the leading edge of airfoil to induce transition phenomenon, which is the reason why the Transition SST model performs better than the SST k-ω model.

論文審定書 i
誌謝 ii
中文摘要 iii
Abstract iv
目錄 v
圖次 vii
表次 viii
符號說明 ix
第一章 緒論 1
1.1 研究背景及動機 1
1.2. 文獻回顧 2
1.2.1 動態失速 2
1.2.2 紊流模型 7
第二章 研究方法 9
2.1 數值方法與紊流模型 9
2.1.1 SST k-ω model 10
2.1.2 Transition SST model 12
2.2 計算相關設定 15
2.2.1 機翼擺動模式 15
2.2.2 網格設定 15
2.2.3 邊界條件 17
第三章 結果與討論 18
3.1 數值結果與實驗之驗證 18
3.1.1 平板測試 19
3.1.2 Case 1 20
3.1.3 Case 2 22
3.1.4 Case 3 24
3.1.5 Case 4 25
3.2 動態失速現象驗證及分析 27
3.2.1 Case 4 kf =0.1流場分析 27
第四章 結論與建議 35
參考文獻 37

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