Passive maintenance of high angle of attack and its lift generation during flapping translation in crane fly wing

Abstract

SUMMARYWe have studied the passive maintenance of high angle of attack and its lift generation during the crane fly's flapping translation using a dynamically scaled model. Since the wing and the surrounding fluid interact with each other, the dynamic similarity between the model flight and actual insect flight was measured using not only the non-dimensional numbers for the fluid (the Reynolds and Strouhal numbers) but also those for the fluid-structure interaction (the mass and Cauchy numbers). A difference was observed between the mass number of the model and that of the actual insect because of the limitation of available solid materials. However, the dynamic similarity during the flapping translation was not much affected by the mass number since the inertial force during the flapping translation is not dominant because of the small acceleration. In our model flight, a high angle of attack of the wing was maintained passively during the flapping translation and the wing generated sufficient lift force to support the insect weight. The mechanism of the maintenance is the equilibrium between the elastic reaction force resulting from the wing torsion and the fluid dynamic pressure. Our model wing rotated quickly at the stroke reversal in spite of the reduced inertial effect of the wing mass compared with that of the actual insect. This result could be explained by the added mass from the surrounding fluid. Our results suggest that the pitching motion can be passive in the crane fly's flapping flight.

Scaling law and enhancement of lift generation of an insect-size hovering flexible wing

“…It has been, for example, shown that wing deformations [13,14] can enhance the force generation and efficiency of a locust operating at Re % 4 Â 10 3 [13], or a hawkmoth at Re % 6.3 Â 10 3 [15]. Moreover, several studies have suggested that insect wing rotations may be passive [16,17], meaning that the resulting rotation is due to a dynamic balance between the wing inertial force, elastic restoring force and fluid dynamic force.…”

Flexible Wing Kinematics of a Free-Flying Beetle (Rhinoceros Beetle Trypoxylus Dichotomus)

“…On the other hand, other insects usually have small Reynolds number. The Reynolds number is from 100 to 200 for Drosophila melanogaster [27] , around 333 for Crane fly [28] , from 1200 to 3000 for Bumblebee [29] , around 1140 for dragonfly [13] , and from 250 to 500 for smallest dragonfly [30] . There were 53 frames for a single stroke, which means that the duration of one cycle (T) lasted 0.027 s and that the frequency (f) was (37.7 ± 0.3) Hz.…”

Numerical study on hydrodynamic effect of flexibility in a self-propelled plunging foil

“…In a series of experimental studies, chordwise and spanwise flexibility have been shown to increase propulsive efficiency in flapping-based propulsion [4][5][6]. In the works by Ishihara et al [7] and Zhao et al [8], a dynamically scaled mechanical model of flapping flight was used to measure the aerodynamic forces on flapping wings of variable flexural stiffness. Due to the complexity of fluid-structure interaction (FSI) problems, in computational simulations simplifications are usually made, either in the model for the fluid or for the structure.…”