Regularities between kinematic and aerodynamic characteristics of flexible membrane wing

The kinematic characteristics of flexible membrane wing have vital influences on its aerodynamic characteristics. To deeply explore the regularities between them, time-resolved aerodynamic forces and deformations at different aeroelastic parameters and angles of attack (α) were measured synchronously by wind tunnel experiments. The membrane motion can be mainly divided into two states at α > 0° with various lift-enhancement regularities: Deformed-Steady State (DSS) at pre-stall, and Dynamic Balance State (DBS) at around stall and post-stall. Besides, the mean camber, maximum vibration amplitude, and lift coefficient almost reach their maxima simultaneously within the DBS region. By introducing momentum coefficient C_μ of membrane vibration, positive correlation among amplitude, momentum and lift is successfully established, and the lift-enhancement mechanism of membrane vibration is revealed. Moreover, it is newly and surprisingly found that at different vibration modes, the maximum vibration amplitude and root mean square of vibration velocity present positive and linear correlation with different slopes, and their chordwise locations are basically consistent. Therefore, novel ideas for active control of flexible wing are proposed: by controlling the vibration amplitude, frequency, and mode, while selecting the specific chordwise locations for intensive excitation, C_μ can be efficiently increased. Ultimately, the aerodynamic performance will be improved.