Elastic Wing Deformations Research Articles

Numerical Investigation of Aeroelastic Deformation Effect on the NASA Common Research Model

The risk of the aeroelastic deformation of the wings to the flight safety has become increasingly prominent for commercial transport aircraft due to the requirements for lightweight structure. In this work, Reynolds averaged Navier-Stokes (RANS) method coupled with transfinite interpolation were employed to investigate the influence of static elastic deformation of wing on aerodynamic characteristics of NASA CRM. Both bend and twist distributions were scaled in numerical simulations based on dynamic pressure, which was shown to be reasonable by the compassions between the calculations and measurements. The numerical results show premature flow separation in the middle and outboard of the wing for original configuration. Furthermore, the flow separation was supressed by the upward bending of the wing and negative twist in the leading edge, and the aerodynamic characteristics of the aircraft were improved by the aeroelastic deformation.

Morphological diversification has led to inter-specific variation in elastic wing deformation during flight in scarab beetles.

Insect wing shapes and the internal wing-vein arrangement are remarkably diverse. Although the wings lack intrinsic musculature to adjust shape actively, they elastically deform due to aerodynamic and inertial loads during flapping. In turn, the deformations alter the shape of the wing profile affecting the aerodynamic force. To determine how changes in wing-vein arrangement affect elastic wing deformation during free flight, we compared elastic wing deformations between free-flying rose chafers (Protaetia cuprea) and dung beetles (Scarabaeus puncticollis), complementing the comparison with wing static bending measurements. The broader relevance of the results to scarab beetle divergence was examined in a geometric morphometric (GM) analysis of wing-vein arrangement in 20 species differing in phylogeny and ecology. Despite rose chafers and dung beetles demonstrating similar flapping kinematics and wing size, the rose chafer wings undergo greater elastic deformation during flapping. GM analyses corrected for phylogenetic relatedness revealed that the two beetles represent extremes in wing morphology among the scarab subfamilies. Most of the differences occur at the distal leading edge and the proximal trailing edge of the wing, diversifying the flexibility of these regions, thereby changing the pattern of elastic wing deformation during flapping. Changes to local wing compliance seem to be associated with the diversification of scarab beetles to different food sources, perhaps as an adaptation to meet the demands of diverse flight styles.

Elastic wing deformations mitigate flapping asymmetry during manoeuvres in rose chafers (Protaetia cuprea).

ABSTRACTTo manoeuvre in air, flying animals produce asymmetric flapping between contralateral wings. Unlike the adjustable vertebrate wings, insect wings lack intrinsic musculature, preventing active control over wing shape during flight. However, the wings elastically deform as a result of aerodynamic and inertial forces generated by the flapping motions. How these elastic deformations vary with flapping kinematics and flight performance in free-flying insects is poorly understood. Using high-speed videography, we measured how contralateral wings elastically deform during free-flight manoeuvring in rose chafer beetles (Protaetia cuprea). We found that asymmetric flapping during aerial turns was associated with contralateral differences in chord-wise wing deformations. The highest instantaneous difference in deformation occurred during stroke reversals, resulting from differences in wing rotation timing. Elastic deformation asymmetry was also evident during mid-strokes, where wing compliance increased the angle of attack of both wings, but reduced the asymmetry in the angle of attack between contralateral wings. A biomechanical model revealed that wing compliance can increase the torques generated by each wing, providing higher potential for manoeuvrability, while concomitantly contributing to flight stability by attenuating steering asymmetry. Such stability may be adaptive for insects such as flower chafers that need to perform delicate low-speed landing manoeuvres among vegetation.

Deformation Control of Highly Flexible Aircraft in Trimmed Flight and Gust Encounter

High-altitude long-endurance unmanned aerial vehicles are inherently highly flexible, and therefore are more susceptible to very large structural deformation in trimmed flight and in atmospheric turbulence. This work aims to avoid these large wing deformations by incorporating and deflecting multiple redundant control surfaces along the leading and trailing edges of the wing. These surfaces are used in both trim optimization to constrain wing deformation to a user-defined value in steady trimmed flight and in minimizing the dynamic response to gust encounter via a feedback controller. Trim optimization is performed using the simplex algorithm. Concurrently, a robust control scheme is designed and applied using loop shaping to demonstrate that, although the control surfaces are used for trimming the aircraft, they have enough authority left to effectively minimize elastic wing deformations during gust penetration. The aforementioned methodology is demonstrated on a highly flexible flying wing. Trim optimization effectively allows trimmed flight at various load factors in the flight envelope while maintaining small structural deformations. The designed controller significantly reduces the maximum wing deflection experienced by a gust disturbance, which is bounded below a user-specified value.

D314 蝶の飛翔における翅の挙動

In order to clarify the flight mechanism of butterfly, we have observed the butterfly flight using high-speed camera. The Test butterfly is Cynthia cardui and its diameter is 25mm in wing chord length, 30mm in wing span length, 254mm2 in wing area and 160mg in weight. Especially, we have discussed the dynamic behavior of butterfly wing in flight motion, such as the elastic deformation of wing, the trajectory of wing tip and the flapping angle of wing. In flight motion of butterfly, the wing carried out elastic deformation not only in the wing span direction but also in the wing chord direction. The flapping angle shows the periodic triangular waveform and the ratio of between the up stroke and down stroke of flapping motion is about 1:1.25.