Flapping and flitting butterflies have long inspired poets, singers and even boxers. Now their motions are inspiring researchers to understand how winged insects get from place to place.

            "As the phrase 'float like a butterfly' shows, butterflies elegantly fly around," said study author Naoto Yokoyama, an assistant professor in aeronautics and astronautics at Kyoto University in Japan. "We would like to understand how they fly in the viewpoint of the fluid dynamics."
            “ 像‘如蝶般飄行’這個說法所表達的一樣，蝴蝶優雅的四處飛舞，”日本航空航太大學助教，論文作者菅直人橫山說。“我們願意在流體動力學視角下，理解蝴蝶是怎麼飛的。”

           Yokoyama and his colleagues created numerical simulations of a butterfly's forward flight. They modeled a chestnut tiger butterfly as four rigid bodies: a football-shaped thorax that lies between the head and the abdomen, the abdomen, and left and right thin, flat wings.
           橫山和同事們創造了蝴蝶前向飛行的數字仿真模擬。他們將一隻栗虎蝴蝶建模為四個不運動的部分：一個足球狀的胸部（在頭和腹部中間），腹部，左、右薄且平坦的翅。

           The researchers ran three different simulations of this mathematical butterfly, and found that the insect used the forces from teensy whirlpools in the air created during each flap of its wings to create lift. They noticed that the butterfly's flight was bumpy as it moved through the air, with lots of ups and downs as it pushed itself forward.
研究者們運行了三個不同的數位蝴蝶模擬類比，發現昆蟲用產生上升力時每次翅膀的扇動製造了氣體中的很多小漩渦。他們注意到，蝴蝶在氣體中運動時，是顛簸的，在它推進自身向前時伴隨著許許多多的上升下落。

           There were some surprises in the tiny flows of air surrounding the butterflies. "The flow around the butterfly is much more turbulent than expected," says Yokoyama.


           The researchers surmised that the minute bumpiness of the air causes butterflies' signature flit, and also may help protect them against predators – the more they duck and weave, the harder it is to catch them. The research was published earlier this year in the journal Physics of Fluids.
           研究者們推測，氣體中小小的顛簸導致了蝴蝶的標誌性飛行，並且可能對抵禦捕食者有幫助--。

           Ty Hendrick, a biologist at the University of North Carolina in Chapel Hill, says that the research matches what has been noticed in the real world. "Butterflies appear more unstable than most other insects, and other available evidence suggests that their erratic flight paths are an anti-predator mechanism as the authors note," he said. "Toxic or distasteful butterflies are known to have smoother and or slower flight paths than edible varieties."
       
           Hendrick said the new research does well to combine state-of -the-art computational fluid dynamics with 17th-century Newtonian mechanics for a flapping animal. "The main missing component from the simulation is including the changing shape of the butterfly's wing. This is known to improve flight efficiency and might also have helped stabilize the forward-flying butterfly," he said.
           Hendrick 表示，這份新報告在一隻扇翅膀的動物上很好的結合了國家最先進的計算流體力學與17世紀的牛頓力學。“這個類比程式中主要的遺失部分包括蝴蝶翅膀的變型。這一點已知是提高飛行效率的，並且可能還幫助穩定前向飛行的蝴蝶。”

Cameras help uncover the mysteries of flight

           Simulations are helpful, but so is direct observation when it comes to understanding insect flight. Tiras Lin, an undergraduate researcher at Johns Hopkins University, is working on a project similar to Yokoyama's to better harness the power of fluttering flight.
           模擬很有用，但在理解昆蟲飛行時也引導著觀測。Tiras 正在進行一項與橫山類似的研究專案，目的在於更好的掌握輕盈地飛舞的力量。

           Lin said that the mysteries of insect flight – how a Monarch butterfly is able to make a 90-degree-turn in a distance shorter than its body size, or a fruit fly is able to easily land upside down on a ceiling -- have confounded researchers for decades.


           Lin has been using high-speed video, along with dissection, to observe the movement of lightweight wings on a butterfly. Through dissection, the researchers estimate the masses of the various parts of the insect body -- including the head, the body, and the wings.

           For the experiments, the researchers keep Painted Lady butterflies in a glass aquarium that is illuminated intensely with multiple bright lamps. Three high-speed cameras with close-focusing lenses captured videos of the butterflies' maneuvers. The researchers record 3,000 frames per second because the butterfly flaps its wings approximately 20 times every second.
           在這個實驗中，研究者們把上色的夫人蝶關在玻璃觀察室裡，觀察室由數個明亮的燈泡高度照明。三個配備了短焦距鏡片的高速攝影機記錄蝴蝶的飛行操縱。研究者們以3000幀/秒的速度記錄，因為蝴蝶以大概每秒20次的速度扇動它的翅膀。

           "This data allows us to mathematically document the motion of the wings and body of the butterfly," said Lin. So far, he says that the wings seem to play a big role in the physics of flapping flight.
      “這份資料讓我們可以將蝴蝶翅膀和身體的活動數位化存檔。”

           "Athletes such as ice skaters and divers move their arms and legs around in order to modify the spatial distribution of their mass; this influences their maneuverability, and specifically, the rotation of their body," said Lin. "Through our research, we believe that it is possible that an insect may be able to do something similar with its wings and body."
           運動員，比如溜冰選手或潛水運動員擺動他們的手臂和腿以改變他們體重的空間分佈；這影響著他們的身體可操作性，尤其是身體的旋轉，“  Tiras 說  ”通過我們的研究，我們相信，一隻昆蟲可能可以做類似的事情，在它的翅膀和身體參與下。

           Lin and other researchers are looking at ways that butterfly flight could help design the next generation of micro-aerial vehicles, to carry out reconnaissance missions or monitor the environment.

           "One area in which micro-aerial vehicles are currently lacking is maneuverability, and due to the small size of modern designs, there is much that can be learned from the flight dynamics of insects such as butterflies," said Lin.
           “高空作業車現今的一個滯後領域就是它的可操作性，同時，因為現代設計的小型體積，我們還有很多東西可以從昆蟲（比如蝴蝶）的飛行動力學中學習。” Tiras 說。