豆娘不對稱拍翅動作與飛行操控研究

Wing Kinematics Measurement and Aerodynamics of a Damselfly with Asymmetric Srokes during the Free Flight

梁家銘(Jia-Ming Liang)

指導教授 ： 楊鏡堂

國立臺灣大學/工學院/機械工程學研究所/碩士(2018年)

https://doi.org/10.6342/NTU201803754

摘要

相對於其他飛行生物，豆娘翅膀具有較高旋轉自由度，可以調整四個翅膀運動，達到加速、急停的目的。本研究於實驗發現，豆娘翅膀上、下拍會有不同(不對稱)的攻角現象，以及傾斜的拍撲方式和特殊的翼尖軌跡，前人研究多以拍撲機構或固定式飛行討論運動參數對飛行的影響，然而運動參數在自由飛行下的空氣動力學卻不得而知。因此，本文結合生物飛行實驗和數值模擬，探討豆娘(白痣珈蟌)飛行，了解其特有的翅膀運動模式下的操控加速度方式。
動作分析部分，本文以ImageJ軟體量化翅膀三個尤拉角(Euler angles): 拍撲角、偏離角、旋轉角。研究發現，懸停下，下拍攻角(αd)會高於上拍攻角(αu)，使得下拍產生向後加速度，達到減速、後退的效果，而需要的單位質量功耗較高。前飛時，上拍攻角會高於下拍攻角，在上拍會產生向前的加速度，所需的功耗較低。拍撲角分析結果顯示，兩翅幾乎同時下拍，但上拍時，前翅速度會加快，提前達到最高點，等待後翅到最高點後再同時進行下一次拍撲。另外，經過計算，本研究也發現後翅傾斜角與飛行模式呈現高度相關(飛行模式以無因次參數B、J量化)，表示當速度越快時，傾斜角越大，反之越小。而兩翅翼尖軌跡則幾乎呈字母「O」形狀。
為了分析翅膀的空氣動力學，本研究透過Fluent建立三維、暫態下的豆娘自由飛行流場。發現升力主要集中於下拍，其中前翅約佔了其中的57%，其產生較多升力的原因在於，後翅容易受到前翅下拍的脫離渦漩的影響，翼前緣渦漩形成緩慢、強度較弱，造成前翅下拍升力越強時，後翅上拍的升力就越弱。這樣的前、後翅交互作用，造成當後翅用來操控加速度方向、前翅用來提供升力時，有較好的飛行效率較高。
綜合以上，本文橫跨生物、流力和工程領域，從仿生和科學的角度解釋豆娘飛行操控方式。簡單來說，本文先量化翅膀的旋轉運動，再釐清不同翅膀動作參數與豆娘加速、減速操控方式的關聯，發現豆娘會利用上下拍不同的拍翅動作，產生不同方向的加速度。最後，發現後翅受到前翅影響，升力表現較差，相比之後，較適合用來飛行操控，前翅則適合提供升力。
經過成千上萬年的生物競爭、演化過程，豆娘發展出輕盈、靈活的飛行方式。本研究成果讓未來在設計以豆娘為參考對象的微飛行器時，對於翅膀對飛行操控的機制，提供有生物依據的操控方法。

關鍵字

仿生飛行 ； 翅膀運動 ； 不對稱拍撲 ； 前後翅交互作用 ； 操控

並列摘要

In the current study, we integrate high-speed photogrammetry and computational fluid dynamics to investigate how wing kinematic parameters are used to control the aerodynamics of a damselfly (Matrona cyanoptera) during free flight. The parameters we measured are the angles of attack during the downstroke (αd) and upstroke (αu), flapping angle ("ψ"), deviation angle ("ϕ") and inclined angle. Effects of asymmetric wing kinematics on the force control are analyzed in detail.
Quantitative measurements and our computational simulations show that the asymmetric angles of attack have a significant influence on the force control. Higher αd and lower αu would generate backward acceleration with more aerodynamic power (Paero), and lower αd and higher αu tends to produce thrust with less Paero . In addition, there is a direct correlation between the dimensionless parameters J and B, and inclined angle, especially for the hindwing. In the flight we considered here (0.15≤B≤1.37), most wing deviations result in an oval wingtip trajectory. Forewings and hindwings would move at the same time during the downstroke, but we find out forewings would flap faster than hindwings in the upstroke.
Furthermore, the influence of wing-wing interactions on the aerodynamic performance is also considered. It is found that the detached LEV from forewings in the downstroke causes a downward flow field near hindwings, which would have a negative effects on the growth of the LEV for hindwings. Due to the disturbance, the hindwing are more efficient to generate the horizontal force with asymmetric angles of attack, and the forewing is recommended for the vertical force generation owing to stronger LEVs with symmetric angles of attack. Consequently, this study suggests that the adjustment of αd and αu is an effective way to control the aerodynamic force and the wing-wing interaction would reduce the strength of the LEV of hindwing.

並列關鍵字

damselfly flight ； wing kinematics ； inclined flapping wing ； wing-wing interaction ； angle of attack

參考文獻

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