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  • 學位論文

綠繡眼高操控性飛行之生物力學研究

On the Biomechanics of Maneuvering Flight for a Small Bird (Zosterops japonicus)

指導教授 : 楊鏡堂

摘要


本研究以綠繡眼為研究目標,探討小型鳥類高操控性的飛行能力為主旨,在生物力學方面總共歸納出綠繡眼的懸停轉彎機制、視覺穩定機制、下拍時的空氣總作用力位置與角度變化以及綠繡眼藉由尾翼開合來調整其身體姿態的俯仰擺動機制。除了綠繡眼的操控飛行能力外,本文還探討了鳥類波浪狀翼後緣之氣動力影響與粒子影像測速儀實驗用粉末對於流場觀測影響。本文所使用的研究方法包含流場可視化實驗、動作分析、理論計算、數值模擬與快速模型成形以及風洞測力實驗。 綠繡眼不像蜂鳥一樣長時間懸停,而是在二到三週期的懸停後就會轉身飛走。這種轉彎模式只需要約1/10翼展長的旋轉半徑以及不到0.2秒的時間即可完成。經由實驗觀察本文發現在懸停階段的綠繡眼會將其身體角度從約40°調整至將近 90°,減少約40 %的身體轉動慣量。接著藉由二到三週期的撲翅運動轉身。本文提出由於在狹小環境中的鳥類必須減少轉彎時的迴轉半徑,因此綠繡眼的轉彎策略是以側滾取代迴轉半徑大的偏航,也因此需要先藉由兩到三週期的懸停來調整身體的角度。調整身體角度趨近筆直不僅使對於旋轉軸的轉動慣量下降,也使得翅膀容易拍擊空氣得到有水平方量的反作用力,以供旋轉所需的力矩,整體上來說都是更容 易實行側滾這個動作。 由於綠繡眼的非對稱懸停只有下拍時會產生升力,因此為了維持定點飛行在下拍中必須產生大於體重的力,因此身體必然會晃動,但綠繡眼巧妙的利用雙翅控制空氣反作用力的位置與方向,使的反作用力不通過質心,讓身體產生俯仰旋轉,雖然使身體的動作變成較複雜的二維運動,但是這旋轉與原本身體的移動恰好會在頭部抵銷,穩定視覺,幫助綠繡眼在懸停時可以穩定的觀察環境並決定飛行策略。但上述的身體旋轉對於綠繡眼的飛行姿態而言是一個不穩定的動作,如果不加以制止並快速恢復原本姿態的話綠繡眼可能會失去平衡而在空中翻轉。由高速攝影照本研究發現綠繡眼在下拍中後期身體便會開始停止抬尾方向的旋轉,接著經歷一壓尾方向的旋轉並回復到原本姿態,如此週期反復。藉由流場可視化技術本研究發現綠繡眼會刻意張開其尾羽攔截翅膀在下拍時所牽引之下衝氣流,這股氣流在尾翼上方仍然相當強勁。此氣流形同一外力將抬起的尾巴壓下並回復身體姿態。數值模擬計算結果顯示施加在全開尾翼上之最大作用力為閉合尾翼的2.6倍。以上結果表明張開之尾羽有助於產生一個壓尾方向的快速旋轉,幫助回復並穩定其身體姿態。 PIV所提供的資訊只能顯示綠繡眼下拍時升力的大小,並無法告知合力的位置與方向,只能由實驗大致觀察出作用力位於質心之前或是之後,本文利用綠繡眼懸停時眼睛穩定的特別現象,使用動力學公式直接解出每一瞬間空氣作用力的位置,結果顯示在為了達成視覺穩定的前提下,空氣作用力位置在下拍過程中會不斷的改變,根據需要有可能會在質心之前或是之後。 以上所有從綠繡眼身上發現的操控性飛行技巧在了解其原理後都可將其概念運用在未來新型微飛行器,使微飛行器的操控性有突破性的發展。此外,本文也展現出在研究如生物力學等複雜議題時可以多元採納各種研究方法並將其整合以致突破現有困境。

並列摘要


Concerning the mechanisms of maneuvering flight of a small bird, this study discovers and explains how a small bird executes a sharp turning maneuver, stabilizes its vision in downstroke exploiting an aerodynamic trick and spreads its tail to facilitate a rapid recovery of its body posture during hovering from a mechanical perspective. Given the stabilized-eye condition, the centre and direction of the aerodynamic force are accordingly determined. Moreover, a particular characteristic of wings in some bird species, the wavy trailing-edge, is discussed whether it has influences over the aerodynamic efficiency for a wing. The formation of regions short of seeding particles in PIV experiments is also explained in this work. The methodology in this study includes flow visualization experiments, computational fluid dynamics, high-speed motion analysis, theoretical calculations for kinematic and fluid dynamics, rapid prototype manufacture and wind-tunnel experiments. A specific type of turning maneuver, termed as ‘hovering turn’, was experimentally identified; this turing maneuver is evidently distinct from the yaw or bank to turns that are well documented in the literature. The hovering turn is characterized by a turning radius only about 1/10 of the wingspan, and requires less than 0.2 s. The reorientation of the bird’s body is invariably preceded by a brief hovering stage during which the elevation angle of the bird increases from 40° to approximately 90°, leading beneficially to a considerable decrease (40% of its maximum) in the moment of inertia of the body against the axis of rotation. The brief hovering is deemed a strategic, preparatory and transitional stage in executing a roll-dominated turn that is efficient and particularly suitable for a small or clutterd space. A passerine generates a lift force greater than its body weight during downstroke, leading to a substantial swing of the bird body, but the bird’s eyes are nearly stable. Employing digital particle-image velocimetry, this study demonstrates that a hovering passerine generates a lift force acting dorsal to the center of mass, concurrently resulting in rotational and translational displacements of the bird’s body. The most notable finding is that the rotational and translational displacements at the bird’s eyes almost cancel each other, leading to the stabilization of the eyes. During a downstroke, a White-eye’s body undergoes a remarkable pitch-down motion, with the tail undergoing an upward swing. This is an unstable arrangement that should be well controlled for a hovering bird. This study shows that the pitch-down motion becomes appropriately suppressed at the end of the downstroke; the bird’s body posture then recovers gradually to its original status. Employing digital particle-image velocimetry, this study doscovers that the strong downward flow induced by downstroking the wings serves as an external jet flow impinging upon the tail, providing a depressing force on the tail to counteract the pitch-down motion of the bird’s body. Spreading of the tail enhances a rapid recovery of the body posture because increased forces are experienced. The maximum force experienced by a spread tail is approximately 2.6 times that of a non-spread tail. This study here proffers an analysis based on kinematic theory and experimental flow visualization to complete the treatment of the aerodynamic force affecting a hovering bird; the centre and direction of the aerodynamic force are accordingly determined. In particular, the principal condition to resolve the problem is the stabilization of the eye of a passerine. Seeing the aerodynamic force from a bird’s-eye view, we find that the centre and direction of this aerodynamic force vary continuously, and the variations are strongly related to that of the lift force. The main contribution of this dissertation includes not only those novel mechanisms of maneuvering flights of a small bird but also an illustration and a guide to bridge between animal behavior and engineering application. Moreover, this study shows that it is beneficial to incorporate various distinct methodologies to deal with complex issues such as biomechanics.

參考文獻


唐振翰 2012 鳥類拍撲翼飛行對翼地效應的影響. 台灣大學機械工程學系碩士論文.
章聿珩 2010 運動學參數對鳥類拍撲翼之升力影響. 台灣大學機械工程學系碩士論文.
劉玠成 2009 綠繡眼懸停飛行機制研究. 清華大學動力機械工程學系碩士論文.
丁上杰 2009 魚類操控式游動之流體動力與生物物理學研究. 清華大學動力機械工程學系博士論文.
Adrian, R. J. 2005 Twenty years of particle image velocimetry. Experiments In Fluids 39, 159-169.

被引用紀錄


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王相博(2013)。蝴蝶撲翼姿態對飛行影響之研究〔碩士論文,國立臺灣大學〕。華藝線上圖書館。https://doi.org/10.6342%2fNTU.2013.02521

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