臺灣博碩士論文加值系統

本論文的目的是針對各種飛行生物拍撲翼翅之氣動力特性進行研究，模擬翼形包括橢圓翼、NACA0012及可撓性NACA0014，流場主要求解Navier-Stokes統御方程式，以獲得相關流場之參數。計算域則以複合式一致性網格系統建構，運用動態網格技術配合C語言程式控制技巧，以實際模擬生物翼翅拍撲之動態行為。
初期採用橢圓翼形(1:8)為蜻蜒翼翅的拍撲模型，藉由簡化之平移、旋轉作為運動機構，在非穩態流場計算中，結合動態網格技術以控制網格配置。重點於分析橢圓翼拍撲運動下所産生的升力與推力，同時亦針對翼翅厚度做進一步之分析，模擬中使用1/4、1/8及1/12不同厚度之翼翅做氣動力特性比較，結果顯示氣動升力會隨著翼翅變薄而提昇。
其次，針對八字形滯空拍撲傾角及縱橫比參數對氣動力特性的影響做完整之分析與比較，目前結果顯示，當採取水平拍撲模式時，質量比功率隨著傾角的增加而呈現出指數型態上升之趨勢。八字形拍撲之縱橫比每增加0.1，則可以提昇約15%左右之平均升力，而質量比功率僅呈現出近似線性的增加，除此，當縱橫比超過0.2後，會在拍撲週期內造成較大之升、阻力變化，對滯空飛行穩定性有不利之影響。
最具貢獻的模擬為撓性翼拍撲之分析，運用向量幾何理論，以C語言控制複雜的網格變形，將撓曲的翼翅拍撲運動與非定常流場分析做緊密之耦合計算。結果顯示，以較低雷諾數撓性拍撲飛行時，須以較高之拍撲頻率方可達到最佳推進效率，當撓性拍撲處於最高推進效率時，Strouhal數維持在約0.255左右，與學者研究觀察結果相符合。而當撓度ao=0.1時，推進力則可以達到最高。當撓度ao>0.5時，撓性拍撲計算之平均水平作用力呈現阻力狀態。以效率而言，撓度ao=0.3時具有最高之推力效率（值達30.73%）。
延續可撓性單翼拍撲之非定常流場分析，進一步研究雙翼可撓性對拍之氣動力特性，在研究規劃中，採用曲率半徑方式描述雙翼撓性拍撲之運動，目的是為了使雙翼對拍之高撓度變形不致産生弦長過度延伸情況，使撓性動態模擬結果更為真實合理地呈現。撓性雙翼拍撲運動模擬之結果顯示，當撓度ao=0.1時拍撲推力達到最高，此時撓性雙翼對拍之推力則比單翼拍撲放大了2.52倍，極具正面之貢獻。從推進效率角度觀察，發現雙翼對拍之最高推進效率落於撓度ao=0.25，其推進效率值達到31.16%，與單翼比較差翼不大。
經過各種不同翼形、參數驗證及研究成果，未來將嘗試進一步分析3D拍撲模式，以更真實之3D實體拍撲模型，完成預測模式之建立，快速有效地計算出最佳參數組合，提供拍撲微飛行器設計之重要參考。

This dissertation aims to study the aerodynamic characteristics in flapping motions. Three kinds of wings have been investigated, which consist of the elliptic, NACA0012 and flexible flapping NACA0014 foils. All parameters about the various dynamic behaviors are calculated by Navier-Stokes governing equations. The computational domain is constructed with a combination of conformal hybrid mesh and dynamic mesh techniques. In addition, C program is applied to develop computer code available in representing the continuous deformation of the flapping airfoil.
Firstly, an elliptic foil with an aspect ratio of 1/8 is used for the test model that is regarded as the wing of dragonfly. The trajectory of flapping motion could be expressed as a formula that indicates the combination of translational and rotational motions. And then, a superior dynamic mesh technique can be applied in the computation. This study is mainly emphasized on understanding the relationship between lift and thrust forces evaluated by the pre-described flapping motions. Besides, the elliptic wing is evidenced that the aerodynamic lift force can be obviously enhanced at low aspect ratios. The simulated result shows that the best aspect ratio is 1/12 in all test runs.
Furthermore, The effects of inclined angle and amplitudes of strokes on the aerodynamic performance are most concerned for a hummingbird in hovering flight in this study. The simulated result of the eight of figure-of-eight flapping motion presents an exponential relationship between the flapping mass-specific power of hovering flapping and inclined angle in horizontal flapping motion. The present results reveal that the lift force will be enhanced about 15 % with every 0.1 increasing of the ratio vertical to horizontal amplitude, while the trend of mass-specific-power exhibits a linear rising type. Besides, a flapping motion with the ratio vertical to horizontal amplitude over 0.2 will cause drastic variation of lift and drag forces along with time. This variation will affect the flight stability during normal hovering.
Modeling the “flexible” flapping wing is the most contributed work in this dissertation. By vector geometry theory, a complicated computer code is developed to control the dynamic meshes, and by which the deformation of the flexible flapping airfoil could be practiced. The results indicate that the optimum propulsive efficiency could be achieved at the condition of higher flapping frequencies while Reynolds number (Re) is low. The highest propulsive efficiency is corresponded to Strouhal number (St) of 0.255, which coincides with the investigations by other researchers. The maximum value of thrust power coefficient is occurred at the flexure extent of 0.1. Drag-indicative wake structures would be formed when the flexure extent is larger than 0.5. And the propulsive efficiency is up to 30.73% at a flexure extent of 0.3.
Based on the results of single flexible flapping, the effect of the deformation for a biplane counter-flapping airfoil could be understood. In addition, a curvature radius method is applied to avoid non-rational extensions occurred during the re-allocation of dynamic meshes. The maximum propulsion for the biplane counter-flapping airfoil could be found at the flexure extent of 0.1, which is 2.52 times to that for the single flexible airfoil. The great contribution to propulsive capability is made by flexible biplane counter-flapping. At the flexure extent of 0.25, the propulsive efficiency is increased to 31.16%.
In this work, it is expected these results could be extend to 3D modeling. Then, some useful suggestions to the design of micro air vehicles (MAV) would be further provided.

目錄

誌謝 ii
摘要 iii
ABSTRACT v
目錄 vii
表目錄 x
圖目錄 xi
符號說明 xv
1. 緒論 1
2. 文獻回顧 4
2.1 生物飛行運動的研究 4
2.2 昆蟲飛行的機制 7
2.2.1 升力的來源 7
2.2.2 推力的來源 13
2.3 數值模擬研究 17
3. 拍撲翼問題描述 21
3.1 尺度律上的考量 21
3.2 運動特性參數探討 22
3.3 非定常流場之研究 25
3.4 可撓（彈性）翼之探討 27
4. 研究方法 30
4.1 統御方程式 30
4.2 數值方法 32
4.3 網格系統 37
4.4 動態網格(Dynamic Mesh)之技術 39
4.5 網格獨立測試(Mesh Independent Test)程序 41
4.6 驗證案例 42
4.6.1 圓柱突然運動之暫態流場驗證 42
4.6.2 有攻角單翼振盪流場驗證 42
4.6.3 剛性翼動態拍撲流場驗證 43
5. 結果與討論 54
5.1 蜻蜓橢圓翼拍撲非定常流場分析 54
5.1.1 橢圓翼翅拍撲運動描述 54
5.1.2 計算模式及數值法則 55
5.1.3 橢圓翼拍撲運動下升阻力特性分析 56
5.1.4 翼翅厚度效應分析 59
5.1.5 小結 61
5.2 八字形拍撲分析 72
5.2.1 運動型態描述 72
5.2.2 計算模式及數值法則 73
5.2.3 標準翼NACA0012與橢圓翼水平拍撲氣動力特性比較 75
5.2.4 不同傾角ao之非定常氣動力特性分析 76
5.2.5 不同縱橫比(Sb/Sa)之八字形拍撲非定常氣動力特性分析 78
5.2.6 小結 80
5.3 可撓性單翼拍撲之效率分析 95
5.3.1 可撓性拍撲運動 95
5.3.2 拍撲推進效率參數 96
5.3.3 可撓性拍撲升阻力及壓力場變化分析 98
5.3.4 可撓性拍撲相位分析 100
5.3.5 可撓性拍撲推進效率分析 101
5.3.6 雷諾數(Re)及對比頻率(kr)對可撓性拍撲之影響 102
5.3.7 小結 103
5.4 可撓性雙翼對拍之效率分析 114
5.4.1 可撓性雙翼拍撲運動 114
5.4.2 雙翼與單翼拍撲推進力之比較 115
5.4.3 不同撓度對可撓性雙拍系統之影響 116
5.4.4 可撓性雙翼拍撲推進效率分析 117
5.4.5 雷諾數(Re)及對比頻率(kr)對可撓性雙翼拍撲之影響 118
5.4.6 小結 119
6. 總結 130
6.1 結論 130
6.2 未來展望與建議 132
參考文獻 134
附錄 142
附錄壹 橢圓翼拍撲運動UDF程式 142
附錄貳 八字型拍撲運動UDF程式 143
附錄參 單翼撓性拍撲運動UDF程式 147
附錄肆 雙翼撓性拍撲運動UDF程式 151
論文發表 158
自傳 160

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