Abstract
The pitching kinematics of an experimental hovering flapping wing setup are optimized by means of a genetic algorithm. The pitching kinematics of the setup are parameterized with seven degrees of freedom to allow for complex non-linear and non-harmonic pitching motions. Two optimization objectives are considered. The first objective is maximum stroke average efficiency, and the second objective is maximum stroke average lift. The solutions for both optimization scenarios converge within less than 30 generations based on the evaluation of their fitness. The pitching kinematics of the best individual of the initial and final population closely resemble each other for both optimization scenarios, but the optimal kinematics differ substantially between the two scenarios. The most efficient pitching motion is smoother and closer to a sinusoidal pitching motion, whereas the highest lift-generating pitching motion has sharper edges and is closer to a trapezoidal motion. In both solutions, the rotation or pitching motion is advanced with respect to the sinusoidal stroke motion. Velocity field measurements at selected phases during the flapping motions highlight why the obtained solutions are optimal for the two different optimization objectives. The most efficient pitching motion is characterized by a nearly constant and relatively low effective angle of attack at the start of the half stroke, which supports the formation of a leading edge vortex close to the airfoil surface, which remains bound for most of the half stroke. The highest lift-generating pitching motion has a larger effective angle of attack, which leads to the generation of a stronger leading edge vortex and higher lift coefficient than in the efficiency optimized scenario.
Highlights
The aerodynamics of small natural flyers such as insects and birds have been a research topic of interest in the past decades [1,2,3,4]
The rotation or pitching motion is advanced with respect to the sinusoidal stroke motion
The pitching kinematics for a flapping wing with a sinusoidally-varying stroke velocity were optimized by combining experimental measurements of the aerodynamic forces and a genetic algorithm
Summary
The aerodynamics of small natural flyers such as insects and birds have been a research topic of interest in the past decades [1,2,3,4]. The abilities of natural flyers to perform different tasks under varying flight conditions with high maneuverability are a source of inspiration for the development of micro air vehicles [5,6,7,8,9]. At low Reynolds numbers (Re < 100), flapping wings can operate more efficiently than rotating wings while providing a higher average lift coefficient CL [10,11]. The unsteady aerodynamic phenomena that give rise to the exceptional flight characteristics of flapping wing flyers are very susceptible to slight changes of the kinematics within the flapping cycle. Previous studies have captured and mapped the wing kinematics of low Reynolds number flyers in order to replicate the complex motion of the wings and getting a better understanding of the resulting aerodynamic forces [12,13,14]
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
