Wing Kinematics Measurement and Aerodynamics of a Damselfly with Asymmetric Srokes during the Free Flight
| Autor: | Jia-Ming Liang, 梁家銘 |
|---|---|
| Rok vydání: | 2018 |
| Druh dokumentu: | 學位論文 ; thesis |
| Popis: | 106 In the current study, we integrate high-speed photogrammetry and computational fluid dynamics to investigate how wing kinematic parameters are used to control the aerodynamics of a damselfly (Matrona cyanoptera) during free flight. The parameters we measured are the angles of attack during the downstroke (αd) and upstroke (αu), flapping angle ("ψ"), deviation angle ("ϕ") and inclined angle. Effects of asymmetric wing kinematics on the force control are analyzed in detail. Quantitative measurements and our computational simulations show that the asymmetric angles of attack have a significant influence on the force control. Higher αd and lower αu would generate backward acceleration with more aerodynamic power (Paero), and lower αd and higher αu tends to produce thrust with less Paero. In addition, there is a direct correlation between the dimensionless parameters J and B, and inclined angle, especially for the hindwing. In the flight we considered here (0.15≤B≤1.37), most wing deviations result in an oval wingtip trajectory. Forewings and hindwings would move at the same time during the downstroke, but we find out forewings would flap faster than hindwings in the upstroke. Furthermore, the influence of wing-wing interactions on the aerodynamic performance is also considered. It is found that the detached LEV from forewings in the downstroke causes a downward flow field near hindwings, which would have a negative effects on the growth of the LEV for hindwings. Due to the disturbance, the hindwing are more efficient to generate the horizontal force with asymmetric angles of attack, and the forewing is recommended for the vertical force generation owing to stronger LEVs with symmetric angles of attack. Consequently, this study suggests that the adjustment of αd and αu is an effective way to control the aerodynamic force and the wing-wing interaction would reduce the strength of the LEV of hindwing. |
| Databáze: | Networked Digital Library of Theses & Dissertations |
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