翅膀相位差對豆娘與蜻蜓懸停策略之影響

本文研究白痣珈蟌與善變蜻蜓配合不同拍翅相位差之懸停飛行機制，由懸停動態觀察開始，以高速攝影機記錄飛行動態，並且分析豆娘及蜻蜓兩物種懸停模式的差異，主要由特徵點軌跡動態及翅膀三個重要動態參數拍撲角、旋轉攻角及掃略角進行比較，前人文獻中不乏討論前後翅交互作用及翅膀相位差對空氣動力學參數之影響的討論，然而缺乏由真實生物觀點切入，豆娘習慣於前翅領先拍撲，蜻蜓則與生俱來後翅領先拍撲，因應不同的相位差飛行模式理應有所差異，以此為出發點發展翅膀相位差效應新的觀點。高速攝影機記錄之影片，標記特徵點後之動作分析結果顯示兩者懸停策略不同，蜻蜓拍撲頻率較快，為豆娘之2.3倍，蜻蜓前、後翅膀皆以拍撲平面角7度左右平行拍撲，後翅領先前翅約68.4度，而後翅旋轉角度變化幅度大於豆娘；豆娘的前、後翅之拍翅振幅均大於蜻蜓1.2倍左右，並以前翅領先39.6度拍撲，且以拍撲平面夾角變化而言其前、後翅拍翅自由度較高。豆娘及蜻蜓整個拍撲循環中，蜻蜓翅膀俯轉及仰轉共佔約62%，而豆娘則是下拍平移及上拍平移階段佔約53%。本研究建立豆娘及蜻蜓懸停狀態之數值模型，探討兩者懸停的空氣動力學效應及流場結構特色，豆娘及蜻蜓懸停主要差異在於翼根渦漩，翼根渦漩在翅膀旋轉階段生成且脫落，豆娘細長的翼根形狀，產生之翼根渦漩影響不大；蜻蜓翼根形狀寬厚，其翼根渦漩結構較強，容易在翼根處翅膀後緣附近滯留，並造成前階段尾流滯留於身體附近，對前後翅渦漩貼附產生不良影響，干擾垂直力產生。蜻蜓在上拍受到強大的干擾渦漩影響，是故其後翅採用大幅度的旋轉振幅，輔以較長的旋轉階段時間，以擺脫此強大渦漩結構干擾，且同時受益於旋轉階段前期產生的垂直力峰值，補充上拍損失的垂直力；豆娘則由於尾流迅速脫離，垂直力在上拍及下拍平移期間得以穩定產生，是以較長的翅膀平移時間及較大的拍撲振幅懸停。本研究解釋豆娘及蜻蜓如何應用不同翅膀相位差達到懸停模式，並比較兩者的懸停策略，以上發現可以提供未來發展四翅微型飛行器的飛行策略及翼型選用的參考，舉例來說：四翅飛行器拍翅振幅較小或者翼根形狀較寬的情況，會遇到類似蜻蜓的干擾渦漩問題，可以透過改變翅膀動態，增加翅膀旋轉時間和角度，來提升飛行表現；反之，如果設計上拍翅振幅較大像豆娘，在拍翅策略上選擇比較長的平移階段，旋轉動作可以相對較小。

關鍵字

蜻蜓；豆娘；懸停；翅膀相位差；前後翅膀交互作用；翼根渦漩

並列摘要

Damselflies and dragonflies are natural four-wing flyers whose agile and enduring flight abilities make them successful predators. Considerable research has been devoted to investigating the interactions between their fore and hind wings in preceding years. Even though these two insects are similar in forms and sizes, their flight kinematics are intrinsically different─damselflies normally fly with forewings in lead, while dragonflies fly with hindwings in lead. The difference between flight motions might result in dissimilar performance. From this perspective, the purpose of this study is to investigate and discuss the effect of the phase lag aerodynamically and biologically. The hovering motions of damselflies (Matrona cyanoptera) and dragonflies (Neurothemis ramburii) were recorded with a high-speed camera first. The computational fluid dynamic (CFD) models of two insects were then created to study their transient flow fields. Our results show that, compared to dragonflies, damselflies fly with lower wingbeat frequency, larger flapping amplitude and observable difference of stroke-plane angles between their fore and hind wings. It is known that an insect’s wingbeat can be divided into translational and rotational phases. The research results indicate that the translational phase of a damselfly accounts for 53% of the entire wingbeat motion, and the rotational phase of a dragonfly accounts for 62%. The different lasting time of wings in different phases lead to the changes of flow structure, and further different flight performance of two insects. The CFD results show that dragonflies’ root vortexes impede wake vortexes shedding in upstrokes, which results in the loss of the vertical force, and therefore dragonflies hover with high rotation amplitudes. In comparison, damselflies shed wakes smoothly and the vertical force is steadily produced during the wing translation stage. Damselflies therefore hover with longer translational phases and higher flapping amplitudes. Comparing the wings motions of dragonflies and damselflies in hovering flight, we hope that the findings will provide suitable flight strategies for the designs of four-wing biomimetic micro air vehicles in the future.

並列關鍵字

damselflies ； dragonflies ； wing-wing interaction ； phase lag ； hovering ； root vortexes

參考文獻

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翅膀相位差對豆娘與蜻蜓懸停策略之影響

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