Experimental and Computational Modeling of the Kinematics and Aerodynamics of Flapping Wing

摘要

High-speed videography is used in measuring the kinematic and deformation parameters of the flapping wing. Based on these data, a theoretical analysis of the underlying physics is performed using computational fluid dynamics simulations. The time varying of the pitching angle in the chordwise directions exhibits a significant second harmonic. Results suggest the mechanics of membrane deformations during a flapping cycle is analogous to the buckling of a bistable structure. Noticeably, with an increase in the freestream speed, the downstroke duration increases. The solution to the three-dimensional fluid dynamics problem is constructed using two-dimensional solutions obtained for several sections of the wing by the unproved discrete vortex method. The inertial component is dominant in the normal force coefficient, and hence, added mass is the main mechanism in aerodynamic force production for the studied problem. A normal component of the acceleration of the wing's trailing edge taken with a negative sign is introduced as a kinematic parameter that is essential in flapping-wing aerodynamics. The results show a satisfactory agreement in trends of the acceleration and force coefficients. From the analysis of kinematical changes, it follows that synchronization of acceleration and of the pitching angle is important for achieving maximum values of the vertical force coefficients.