拍撲翼流場之數值模擬

淡江大學機構典藏 > 工學院 > 航空太空工程學系暨研究所 > 學位論文 > Item 987654321/35623

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题名:	拍撲翼流場之數值模擬
其它题名:	Numerical simulation of the flow field of flapping wings
作者:	李柏勳;Li, Po-hsiung
贡献者:	淡江大學航空太空工程學系碩士班陳慶祥;Chen, Ching-shung
关键词:	拍撲翼;拍撲運動;動態網格;Flapping wing;Flapping motion;Dynamic mesh
日期:	2008
上传时间:	2010-01-11 06:52:58 (UTC+8)
摘要:	本文是對於飛行生物的翼翅拍撲行為做空氣動力特性分析，以了解拍撲行為產生升力以及推力的機制。使用FLUENT6.2.16版求解Navier-Stokes方程式來獲得與流場相關的參數。網格系統採用複合式一致性網格系統搭配動態網格技術，能夠更真實的去模擬飛行生物的拍撲運動。首先以較小的飛行生物如蜻蜓的翼翅做為傾斜拍撲運動的模型，並簡化翼翅拍撲的軌跡，再結合動態網格技術去計算二維橢圓翼翅在暫態流場中滯空拍撲所產生的升力與推力。並進一步去改變翼翅厚薄度，分析不同的厚薄度對於所產生的升力以及推力的變化，可以發現當翼翅越薄，升力與推力也會增加。再以較大的飛行生物如蜂鳥的翼翅做為八字型水平拍撲運動的模型，同樣減化其拍撲運動的軌跡，結合動態網格的技術去模擬二維橢圓翼翅在滯空拍撲時所產生的升力以及推力的變化。藉由改變其八字型軌跡的縱橫比，可以分析縱橫比對於升力以及推力的影響。由結果可以發現當縱橫比越大，雖然升力有顯著的提升，但是在縱橫比超過0.2後，週期內的升力及推力的變化也增大而且有負向升力的產生，使得滯空飛行的穩定性大受影響。透過模擬驗証的研究成果，將來可以進一步去模擬三維的翼翅拍撲以及撓曲變化，並找出更為精確的軌跡方程式，使得模擬計算的結果能夠更貼近真實生物拍撲行為的流場，可以提供微飛行器各項參數的設計與參考。 This thesis aims at analyzing the aerodynamic characteristics and understanding the lift and thrust generation mechanisms of flapping wings. The commercial software package, FLUENT (6.2.16 version), was utilized to solve the Navier-Stokes equations to obtain the flow fields. The grid system was constructed by a combination of conformal hybrid mesh and dynamic mesh techniques. This grid system allowed realistic simulations of flapping motions of flying creatures. We first simulated a model wing of dragonfly. The trajectory of the flapping motion was simplified using a mathematical model and the dynamic mesh technique was employed. The unsteady flow field and the corresponding lift and drag were obtained. We then simulated the effect of the thickness of the wing on the aerodynamic characteristics. The results show that a thinner wing has better lift and thrust. We also simulated aerodynamic performance of hummingbirds in hovering flight. The simulated results indicate that the lift and thrust change with the aspect ratio of the flapping motion trajectory. If the aspect ratio exceeds 0.2, then there is significant variation of lift and thrust; negative lift is also generated in some part of the flapping cycle. Such large variation of lift degrades the flight stability of hovering. In the future, we expect the numerical techniques developed in this work can be extended to three-dimensional simulations with wing deflection. The trajectory equation of the flapping motion can also be improved to better simulate the motion of flying creatures.
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