| Summary: | 碩士 === 淡江大學 === 航空太空工程學系碩士班 === 100 === 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.
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