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標題: 蜻蜓翅膀形變:流體效應與振動調控
Wing deformation of dragonfly : Aerodynamic effects and flapping
作者: 蔡峰岳
Tsai, Feng-Yueh
Contributors: 紀凱容
Kai-jung Chi
生物物理學研究所
關鍵字: 薄翅蜻蜓;翅痣;翅膀形變;高速攝影術;流場可視化;生物力學;空氣動力學;材料力學
dragonfly Pantala flavescens;pterostigma;wing deformation;high-speed videography;flow visualization;biomechanics;aerodynamics;mechanics of materials
日期: 2013
Issue Date: 2013-11-18 10:37:35 (UTC+8)
Publisher: 生物物理學研究所
摘要: 翅痣蜻蜓翅膀前緣末端有一顏色加深之構造,稱作翅痣(pterostigma),翅痣為雙層膜之構造,且比他處翅膜厚,面密度也較高。根據我們過去研究,此加重翅膀末端的構造,將會使得翅膀在相同的頻率及振幅振盪下,增加翅膀彎曲形變量。本研究主要分為兩個部分,首先以調控振幅的方式探討翅膀振幅對於彎曲形變的影響。並利用翅膀彎曲與翅膀位置的關係,推算出其間之關係。為進一步探討翅痣的有無對翅膀形變及其周圍流場的影響,我利用流場可視化技術,觀測於相同頻率及振幅下,以正弦波振動的蜻蜓翅膀周圍流場。由於可視化技術限制,此處以較低之風速實驗,並同時將振動頻率調低,以符合活體蜻蜓史卓赫數。研究結果顯示,翅膀的彎曲形變量將會隨著振幅的提高而上升,在去除翅痣前後均然,但在有翅痣翅膀此效應較為明顯;此外,翅膀基部的振動與翅膀末端的位置接近線性關係。風洞實驗中,翅痣去除將會改變翅膀揮動時攻角的變化範圍及其數值大小,而在渦漩行為上,去除翅痣造成的趨勢變化並不明朗。
Pterostigma is a darken region at the leading edge of the wings of many insects. It is bilayer in structure, and is thicker and heavier than the other cells of the wing. Previous study shows that a dragonfly wing with pterostigma would increase wing’s bending deformation at same vibration frequency and amplitude. In this study, I further examined the mechanical characteristics and consequences of pterostigma of dragonfly wings. Firstly, I controlled the vibration amplitudes of the wing base to explore how they affect wing’s bending deformation. Secondly, I applied flow visualization technology to examine the effects of pterostigma, and hence difference in bending deformation, on the flow behaviors around the flapping wings. Because of the limits of ours experimental setup, I used lower vibration frequency for wings in lower wind speed to meet similarity of Strouhal number. The results show that, whether the wing had pterostigma, the wing’s bending deformation was greater when the amplitude increased; however, the effect is more pronounced in wings with pterostigma. Furthermore, the Y-position of pterostigma (i.e. the amplitude of pterostigma) increased with the amplitude of wing base, indirectly implying that a flapping wing with greater bending deformation would also have higher pterostigma position. Results from the wind tunnel experiments show that removal of pterostigma would change the range and angles of wing’s angle of attack. However, the effects of pterostima on the behaviors of vortices are not conclusive.
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