|题名: ||A study of 3-D flapping wing performance under severe weathers|
|作者: ||王唯璋;Wang, Wei-Zhang|
|关键词: ||拍撲翼;動態網格;大雨;DPM;UDF;Flapping wing;Dynamic mesh;Heavy Rain|
|上传时间: ||2013-04-13 11:58:46 (UTC+8)|
|摘要: ||近年來航太科技不斷的創新發展，其中拍撲翼微飛行器是一個目前熱門的研究項目，它可以適用於民事及軍事用途，如監視，偵查及救援等任務上。拍撲微飛行器的特色是體積小、重量輕，飛行時容易受外力所影響，目前的拍撲翼研究大都只考慮到晴空天氣下飛行，忽略了惡劣天氣因素，但在極端氣候不斷肆虐的當下，研究豪大雨影響此其時也。本研究團隊長期研究天氣因素，此處利用商用軟體FLUENT之動態網格機制來模擬拍翼的飛行，大雨的模擬則採用程式內建的DPM模組(Discrete Phase Model)來計算拍撲翼在惡劣天氣下飛行的空氣動力性能。 |
本研究採用了兩種不同的運動行為去模擬不同拍撲翼外形的翅膀，這兩種運動行為分別是Wang氏八字形運動及Trizila 氏移動轉動運動，外形則有橢圓、平板、hawk moth、二維、三維等諸種，經過二維及三維的晴空飛行下驗證後，再進行拍撲翼大雨下飛行模擬。根據吾人研究結果，可以發現幾個重要結論：首先是同樣外形在相同的運動行為下，從二維變成三維時，升阻力之減少符合所知的三維釋放效應；其次則是不同外形會有不同的升阻力狀況；最後比較拍撲翼在大雨和晴空下的飛行數據，二維外形最大遞減率不到9%，而三維外形最大遞減率則高達近70%，大雨在真實三維情況下的影響比想像中嚴重許多。換言之，如果昆蟲生物的翅膀外形及運動是由最佳化演進而得，則此演進過程似乎不包括大雨情況。
In recent years, modern technology was innovated and developed continuously, and now flapping MAV is becoming a prevalent developing project. It can be applied to all military and civilian usages. In order to improve MAV flying performance, a better understanding of insect aerodynamics thus become necessary. There are many researches in flapping-wing studies, but most of these researches only consider that flapping-wing motion under calm weather, ignore some severe weather. However, during the spring and summer seasons in Taiwan, there is thunderstorms, typhoons, etc., and it usually brings heavy rain and strong wind. Therefore, we must consider harsh weather conditions such as heavy rain.
In this thesis the main objective was to investigate the flapping-wing motion under harsh weather. We use numerical method such as preprocessing tool Gambit and CFD software FLUENT as our analytical tools. This model combines with the dynamic mesh in order to implement arbitrary wing kinematics. For present study, the flapping-wing aerodynamic parameters such as lift and thrust in the unsteady flow situation could be correctly generated. Two different mechanisms (Wang’s figure eight motion and Trizila’s translational and rotational motions) are simulated, and models of different profile are further investigated to compare the shape effect. According to the results, we can find two important conclusions. First, we observe the same decreasing behavior in the lift and drag coefficients from 2D to 3D configuration, which can be easily explained and expected from the 3D reliving effect. Second, it is found that the model’s size or shape will generate rather different aerodynamic force under the same motion.
In the heavy rain simulation, the Eulerian-Lagrangian approach could simulate motions of rain drops successfully. Although the results with flapping-wing in 2D case such that the decreasing rate is only less than 9%, imply the aerodynamic degradation was not significant. But for 3D case it was found that the decreasing rate could be as high as 70% under the heavy rain situation, a much more significant aerodynamic degradation effects. It is felt that if flapping configuration and motion are evolution and optimized into its current form, then it has not include the heavy rain circumstances. All in all, when designing any MAVs, we must always consider the severe weather influence.