| The influence of the insect-like wing's chord-wise flexibility on aerodynamic performance and the corresponding flow field during the wing rotation motion in insect's hovering flight is investigated first. The results showed that during the passive rotation, the lift increases following the increasing flexibility till the flexibility reaches an optimal value which produces largest lift and after that lift decreases as the flexibility increases during translation. The drag production always decreases as the flexibility increases. For the active rotation during stroke reversal, although the aerodynamic performance decreases as flexibility increases, the lift-to-drag ratio can reach its optimal value by using a flexible wing. Furthermore, the average lift force was the highest in advanced rotation and that of delayed rotation was the lowest. From the flow field visualization experiments, the leading-edge vortex intensity and shedding time is affected by the chord-wise flexibility.;Then the aerodynamic performance and flow field of rectangular wing model during flapping motion with two kinds of damage: wing area loss and linear cracking are studied. For wing area loss, the aerodynamic performance is influenced by the area loss location and area loss percentage. With the area loss at the same location and size, the flexible wing model provides lower lift when angle of attack is less than 45° compared to the rigid wing model. However, as soon as the angle of attack goes above 45°, the flexible wing has better performance than rigid wing. For linear cracking, the lift increases as the cracking moving from the wing base to the tip and decreases as the cracking length goes higher. DPIV results are provided to visualize the flow field around the wing model and help to better understand the aerodynamic performances. According to the experimental results, guidance for designing of micro air vehicle with flapping wing is stated. |
