旋轉時機與旋轉時間對於豆娘飛行表現之影響

Abstract

本文研究豆娘(白痣珈蟌)的翅膀旋轉時機與旋轉時間對於飛行表現之影響，利用兩台高速攝影機正交攝影技術捕捉豆娘在自由飛行下的動態，並且分析不同旋轉時機以及旋轉時間的效應。首先分析並歸納豆娘的拍翅動作模式，並找出翅膀運動中的五個重要角度：拍撲角、偏離角、旋轉角、傾斜角以及方位角，發現在白痣珈蟌的飛行動作中，有延遲旋轉以及對稱旋轉的差別，旋轉時間從0.17 ~ 0.28個週期不等。在拍翅軌跡上白痣珈蟌前翅採取八字型，後翅則採取O字型方式。而在前後翅相位差的部分約為0.10 ~ 0.15 個週期。 在不同旋轉時機固定來流模擬結果發現領先旋轉產生的垂直力大於對稱旋轉以及延遲旋轉，差異主要是在下拍的時候，由於領先旋轉在下拍初始階段的攻角即為正攻角，因此LEV也較早開始發展；而延遲旋轉則是造成負攻角的現象，使得LEV發展較小。在下拍末期，前翅因為領先旋轉模式先進行翅膀旋轉造成較高攻角的拍撲動作。在自由飛行中，領先旋轉模式所產生的空氣負功相較於對稱旋轉以及延遲旋轉大了64%以及55%，雖然採用領先旋轉的飛行可以飛得較高，但是必須耗費更多的能量來克服空氣產生的負功。 在不同旋轉時間的固定來流模擬中，在垂直力的部分，旋轉時間為0.20、0.25、0.30、0.40以及0.50按照趨勢大致上可以分成三組。在下拍階段，旋轉時間為0.25與0.50相對於旋轉時間為0.30的前翅與來流速度所夾的有效攻角較大，因此在下拍時會產生較大的LEV，但是因為旋轉時間為0.25週期會進行快速的翅膀旋轉，使其在下拍初期垂直力不會相差太多。在自由飛行中，旋轉時間為0.30所需克服的空氣負功較小，因此在低耗能為優點的飛行器上佔有較大的優勢；若是不同飛行模式的需求下，旋轉時間0.30適用於需要較快的水平飛行速度，旋轉時間0.25在適用於需要較高的爬升率，因為在差不多的爬升率中，其所需克服的負功最少。

In the present study, we investigated how the timing and duration of wing rotation affect the flight performance of damselflies (Matrona cyanoptera). The wing motions of damselflies were recorded with two high-speed camera, and then CFD models were built to analyze flow field. In the motion analysis, we measured the flapping angle, the deviation angle, the rotation angle, the inclined angle and the azimuth angle. The results showed that there were symmetric and delayed rotation in damselflies’ flight and the duration of wing rotation was 0.17 ~ 0.28 period. Moreover, we found that the phase difference between forewings and hindwings were 0.10 ~ 0.15 period. In the constant freestream simulation of the different timing of wing rotation, the results indicate that the vertical force with advanced rotation is larger than that with symmetric and delayed rotation due to the different angle of attack in the downstroke. At the beginning of downstroke, the leading edge vortex (LEV) develops earlier with advanced rotation because of the positive angle of attack. On the other hand, the LEV is delayed with delayed rotation contrary to the case with advanced and symmetric rotation. At the end of downstroke, the angle of attack is higher with advanced rotation than that with symmetric and delayed rotation. In the free flight simulation of different timing of wing rotation, the negative work done by air with advanced rotation is 64% and 55% larger than that with symmetric and delayed rotation respectively. Although damselflies can fly higher with advanced rotation, they have to consume more power to counteract the negative work done by air. In the constant freestream simulation of the different duration of wing rotation, the vertical force with duration time of 0.25 and 0.50 are greater than that of 0.30, because the effective angle of attack with the duration of 0.25 and 0.50 is larger. In the free flight simulation, the cases that the duration is 0.20, 0.25, 0.40 and 0.50 are similar in the trajectory, and the climbing rate of these cases are higher than duration time of 0.30. In addition, the advantage of the duration of 0.25 is that it deal with less negative work, and the advantage of the duration of 0.30 is to apply to the MAVs (micro aerial vehicles) with low energy consumption and fast horizontal velocity.