Flow Visualization and Force Measurement of an Insect Wing Based on Dragonfly Hovering

Flow visualization and aerodynamic force measurements were conducted in order to investigate the flow phenomena around the wing of a hovering dragonfly. Two pairs of 4-bar linkage mechanisms were installed in a flapping model and driven by a stepping motor. The foreand hindwing have a phase difference angle of 180°. The stroke amplitude, pitch angle and incidence angle of the model were 75°, 0-90° and 60°, respectively. A wing beat frequency of 0.087 was chosen, and the corresponding Reynolds number was 2.0×10 based on the forewing. Each wing generated LEV at the start of downstroke and the LEV was developed and maintained on the upper surface of the wing. Aerodynamic forces were also generated in the downstroke motion in all cases. When the wings stroke together, the LEV on the hindwing was deformed by the forewing, and the forces on the hindwing are lower than in the hindwing only cases. These results indicate that the wing-wing interaction have a negative effect on the generation of aerodynamic forces.