本研究在低速風洞中探討蝴蝶仿生機構增加尾翅後之空氣動力學效應變化。現今微型飛行器之研究盛行，人們開始對真實飛行生物感到好奇，其中對於鳥類有較多之研究，然而相較於鳥類，昆蟲甚至蝴蝶之研究較少。因此本研究設計兩種不同形狀之蝴蝶翅膀模型，利用壓力敏感技術量測(Pressure Sensitive Paint, PSP)以及粒子影像測速(Particle Image Velocimetry, PIV)兩項技術在低速風洞中，了解其表面壓力分布及流場變化情形，觀察其在滑翔時之空氣動力學差異。
本研究設計一仿真實燕尾蝶擁有尾翅之翅膀模型其展弦比(AR)= 3.65，另設計一擁有相同翅膀形狀但無尾翅之翅膀模型其AR= 3.85，探討攻角(α)= 15°~ 35°時其兩者間空氣動力學效應之差異。本研究在PIV時沿著翼展方向主要探討兩個截面(z*=z/b= 0.12、0.4)之渦流、流場差異，而在PSP時除了探討全表面之壓力，還探討了(z*= 0.12、0.79)在這兩個截面之壓力係數沿著弦長( )方向分布之情況。
首先，從表面壓力結果發現，當增加尾翅時在靠近翼前緣之表面壓力相較於無尾翅之表面壓力來得低，顯示當增加尾翅時，可以維持翼前緣渦流之更穩定生成。且發現沿著翼展方向之壓力分布隨著靠近翼尖而壓力降低，表示本研究蝴蝶之翼面形狀產生之翼尖渦流可以減緩翼前緣渦流分離，使其靠近翼尖有較低之壓力分佈。而從PIV之結果顯示，增加尾翅可以減緩翼後緣渦流之形成，幫助翼前緣渦流更穩定之生成，且從尾流之速度分布可以明顯看到，當增加尾翅時在翼後緣之速度減弱之情況相較於有尾翅之模型來得低，表示增加尾翅可以減緩翼後緣阻力之產生。透過本研究之成果可以更了解蝴蝶之尾翅對於飛行之氣動力影響為何，此實驗結果對於未來微型飛行翼之設計提供參考。

In the present research, we perform a low-speed-wind-tunnel experiment to investigate the aerodynamic performance on a butterfly with and without hindwing tail. Recent years, Micro-air-vehicles (MAVs) that mimic the flight mechanisms of insects have attracted significant attention. Previous research has showed that in the absence of long hindwing tails, the lift and longitudinal static stability are reduced, indicating that the hindwing tails play an important role in enhancing the aerodynamic performance. However, in previous study, the experiments were all conducted at the same angle of attack. The aerodynamic effect of hindwing tail still needs to be studied systematically. To further understand the flight mechanism of butterflies which have relatively low aspect ratio, this research use pressure sensitive paint (PSP) and particle image velocimetry (PIV) to observe the pressure distribution on the upper surface and flow around the wing. Two testing models with/ without hindwing tail which made of aluminum plate with thickness of 0.9 mm were designed. One model with hindwing tail, which has the same shape of a swallowtail butterfly (Graphism policies) and the other just cut the hindwing tail with a round-shape modified.
In this study, the results show that leading-edge vortex is bigger and more stable in the butterfly model with hindwing tail. Secondly, the trailing edge vortex grows slowly in the spanwise direction with hindwing tail, which means the hindwing tail delay the generation of the trailing edge vortex. In addition, while the angle of attack was increased, the strength of trailing edge vortex is increased, and the location of the leading-edge vortex is far from the wing surface. At the angle of attack are 15˚and 25˚, the velocity shows a dramatically decreasing at the region near the trailing edge for the model without hindwing tail. On the basis, this research provides ideas for designing micro aerial vehicles about different shape of the wing for different mission. Under different flight condition, MAVs can improve the flight ability by increasing the hindwing tail.

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