Effects of Wing plane Shape of Flexible Flapping Wing on the Aerodynamic Performance

To investigate the effect of the wing shape on the aerodynamic performance of the flexible flapping wing, the aerodynamic force measurement and visualization were performed on the hawkmoth-like wing and rectangular wing with the same aspect ratio, area and spanwise flexibility. The wingbeat frequencies of the hawkmoth-like and the rectangular wings are 0.125 and 0.1 Hz, respectively, and in the water tank experimental environment of Reynolds number Re similar to 5,000, the experiments were conducted by applying a simplified two-dimensional flapping motion with symmetrical up and downstrokes. As a result, the aerodynamic coefficient graphs of the two flapping flexible wings showed very similar curve shapes. The average lift and drag coefficient values of the two wings were slightly higher for the rectangular wing, and the difference of average lift-to-drag ratio was about 4.1%. As a result of visualization with DPIV, the detailed characteristics of the vortices generated from the two wings were somewhat different, but the overall vortex structures were almost similar. The results of this study imply that the effect of the wing plane shape is not significant if the main characteristics such as the wing area and the aspect ratio are the same, especially if the flapping motion is identical.