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標題: | 蝶型拍撲翼之氣動力研究 A Study of The Aerodynamics of Butterfly-type Flapping Wing |
作者: | Ya-Han Chang 張雅涵 |
指導教授: | 黃美嬌(Mei-Jiau Huang) |
關鍵字: | 燕尾蝶,拍撲飛行,展弦比,微型飛行器, Swallowtail butterfly,Flapping flight,Aspect ratio,Micro aerial vehicles, |
出版年 : | 2012 |
學位: | 碩士 |
摘要: | 因應用途及任務的需要,無人飛行器(UAVs)的尺寸正往逐漸縮小的方向發展。隨著飛行器尺寸的縮小其翅膀的展弦比也隨之變小,若繼續沿用傳統UAVs所使用的固定翼來產生氣動力,將不足以支撐飛行器的重量。在自然界中,昆蟲的翅膀具有低展弦比卻能在空中自在飛行,其生理特徵、運動模式等等,都是開發微型飛行器(MAVs)者可以師法的對象。本研究選定燕尾蝶為研究對象,透過CFD商業軟體ANSYS Fluent探討燕尾蝶型翼在相同的飛行速度時,於不同拍撲頻率及不同攻角下之氣動力性質,並探討燕尾翼構造對於拍撲飛行流場之影響。此外,我們也設計一具相同展弦比之對稱長平板翼,將其氣動力特性與蝶型翼之氣動力特性進行比較,以進一步了解蝶型翼之優點。研究結果發現:燕尾蝶型翼以滑翔飛行時,其升力先隨著攻角上升逐漸增加,於攻角40度時有最大值,若攻角角度繼續增加則升力逐漸下降;而阻力則隨著攻角上升呈現單調漸增的趨勢;於攻角10度時有最大的升阻比。於拍撲飛行時,一週期內之平均升力、阻力及升阻比隨攻角變化的趨勢與滑翔飛行時雷同,惟其值隨拍撲頻率的增加而增大;比較蝶型翼與對稱長平板翼流場之俯仰力矩,發現因為燕尾蝶型具有前掠型的翼前緣,於下拍行程時,作用於翅膀的流場可對身體幾何中心產生一有助於提升攻角之力矩,可能導致升力及阻力的增加;反之,於上拍行程時,攻角角度受到反向力矩作用於身體之結果而降低,升力及阻力也因而減少。此力矩影響攻角大小的現象與前人的實驗觀察有相似之處。透過三維流線分布圖,發現燕尾翼於高頻拍撲飛行之下拍行程中,無論為高攻角或低攻角飛行,於燕尾處會形成較結實的流場結構,推測應有助於流場的穩定。 Corresponding to the requirements of applications and tasks, the size of the unmanned aerial vehicles (UAVs) is tending smaller and smaller. Following the size reduce, the aspect ratio of the UAV wings reduces as well. Consequently, the common fixed-wings are no longer capable of providing enough aerodynamic forces against the gravity. In the nature, insects’ wings have low aspect ratios, but they fly freely in the air. Their physical characteristics and movement patterns must have implications which are useful for developing micro UAVs. This study aimed at the flow fields induced by a swallowtail butterfly in use of the software “ANSYS Fluent.” Parameters such as the flapping frequency, the angle of attack, the wing shape, and the swallowtail effect were explored. The simulation results show: when a swallowtail butterfly-type wing is in gliding, its lift force increases with the angle of attack first but decreases later, peaking at an angle of 40˚. On the other hand, the drag force increases monotonically. Consequently, the lift-drag ratio has its maximum value when the angle of attack is 10˚. The flapping flight has similar variation trends in the average lift force, drag force and the lift-drag ratio to the gliding flight but the magnitudes increase with the flapping frequency. Furthermore, unlike the long flat-panel wing, the butterfly-type wing can seemingly produce a positive pitch moment to rotate its body and consequently increase the angle of attack during the downstroke motion by taking advantage of its forward-swept leading edge. A negative pitch moment is generated during the upstroke motion the other way round. Similar observation had been reported in the literature. Through the 3D-streamline visualizations, it was also found that the swallowtail can help building some solid flow structures in the neighborhood during the downstroke motion when the flapping frequency is high, regardless of the angle of attack. It is believed that these structures are related to the flow field stability. |
URI: | http://tdr.lib.ntu.edu.tw/jspui/handle/123456789/65584 |
全文授權: | 有償授權 |
顯示於系所單位: | 機械工程學系 |
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