柔軟なハチドリ規範型羽ばたき翼の流れ場のPIVによる可視化

抄録

Flapping wings are expected to be beneficial to small flying robots in terms of the large lift with large angle of attack in low Reynolds number flow. We are focusing on hummingbirds which are the only birds capable of sustained hovering flight, and are conducting research toward the realization of small flying objects that imitate them. Although the wing flexibility can improve the aerodynamic lift and efficiency, resultant flow field around the flexible flapping wings have not been fully understood yet. Here, we created two types of hummingbird-mimetic wings and compared their lift, efficiency, and flow field by means of an electric flapping mechanism and PIV (particle image velocimetry). The design difference between the two wings was the number of wing shafts: one has four shafts and the other had eight shafts. The flow field on the wing cross sections near the mid-stroke was two-dimensionally visualized at the flapping frequency of 20 Hz. As a result, the leading-edge vortex was found to be attached to the 4-shafts wing at distal region, producing notable downwash. The efficiency of the 4-shafts wing was better than that of the 8-shafts wing while the lifts are similar to each other.