Lift enhancement by bats' dynamically changing wingspan

Wang, Shizhao; Zhang, Xing; He, Guowei; Liu, Tianshu

doi:10.1098/rsif.2015.0821

Cited by 41 publications

(20 citation statements)

References 47 publications

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“…With these techniques, it has been shown that insects do exhibit time-varying changes in wing shape during flapping flight, and that these dynamic morphings are helpful in efficient aerodynamic force generation [16][17][18]. Generally, in-flight wing shapes of vertebrates are still largely unknown, with a few exceptions, particularly for bats [19][20][21][22].…”

Section: Introductionmentioning

confidence: 99%

Quantifying the dynamic wing morphing of hovering hummingbird

et al. 2017

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Animal wings are lightweight and flexible; hence, during flapping flight their shapes change. It has been known that such dynamic wing morphing reduces aerodynamic cost in insects, but the consequences in vertebrate flyers, particularly birds, are not well understood. We have developed a method to reconstruct a three-dimensional wing model of a bird from the wing outline and the feather shafts (rachides). The morphological and kinematic parameters can be obtained using the wing model, and the numerical or mechanical simulations may also be carried out. To test the effectiveness of the method, we recorded the hovering flight of a hummingbird (Amazilia amazilia) using high-speed cameras and reconstructed the right wing. The wing shape varied substantially within a stroke cycle. Specifically, the maximum and minimum wing areas differed by 18%, presumably due to feather sliding; the wing was bent near the wrist joint, towards the upward direction and opposite to the stroke direction; positive upward camber and the ‘washout’ twist (monotonic decrease in the angle of incidence from the proximal to distal wing) were observed during both half-strokes; the spanwise distribution of the twist was uniform during downstroke, but an abrupt increase near the wrist joint was found during upstroke.

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Section: Introductionmentioning

confidence: 99%

Quantifying the dynamic wing morphing of hovering hummingbird

et al. 2017

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“…Wang et al [48] found that folding motion will increase both the time-averaged lift coefficient and instantaneous lift coefficient. Further research [49,50] revealed that folding motion can also increase the efficiency of lift production and reduce power consumption. Therefore, it may be inadequate to conduct the studies only under static and steady conditions.…”

Section: Comments On Research Modelsmentioning

confidence: 99%

The Progress of Aerodynamic Mechanisms Based on Avian Leading-Edge Alula and Future Study Recommendations

et al. 2021

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Birds in nature have many unique devices to help them acquire excellent flight abilities under various complex flight conditions. One of the unique devices is the leading-edge alula, located at the junction of the arm wing and the hand wing of most birds. It often spreads out during takeoff and landing, probably playing a similar role to high-lift devices in fixed-wing aircraft. This paper analyzed and reviewed the results of current research on leading-edge alula, finding some important factors, such as the complex flapping motions, flexibility, and the plane and section shape of the wing, that have been ignored in current research to a certain extent. These would greatly affect the conclusions obtained. Hence, for a deeper understanding of the aerodynamic mechanisms and functions of the alula, some new study predictions for future research are presented. In addition, the feasible models and methods for further research based on these predictions are discussed and proposed. For example, the higher-accuracy LES or hybrid LES/RANS method and the combinations of these methods with wind-tunnel experiments using PIV technology are recommended.

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“…Since then, certain unsteady mechanisms such as enhanced lift by the leading edge vortex (LEV) have been shown to be nearly ubiquitous in flapping flight, while other mechanisms such as clap and fling are only observed in certain insects operating at smaller length scales. Bats have also been shown to enhance lift by dynamically changing their wingspan [ 9 ].…”

Section: Introductionmentioning

confidence: 99%

Analysis of a 180-degree U-turn maneuver executed by a hipposiderid bat

2020

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Bats possess wings comprised of a flexible membrane and a jointed skeletal structure allowing them to execute complex flight maneuvers such as rapid tight turns. The extent of a bat’s tight turning capability can be explored by analyzing a 180-degree U-turn. Prior studies have investigated more subtle flight maneuvers, but the kinematic and aerodynamic mechanisms of a U-turn have not been characterized. In this work, we use 3D optical motion capture and aerodynamic simulations to investigate a U-turn maneuver executed by a great roundleaf bat ( Hipposideros armiger : mass = 55 g, span = 51 cm). The bat was observed to decrease its flight velocity and gain approximately 20 cm of altitude entering the U-turn. By lowering its velocity from 2.0 m/s to 0.5 m/s, the centripetal force requirement to execute a tight turn was substantially reduced. Centripetal force was generated by tilting the lift force vector laterally through banking. During the initiation of the U-turn, the bank angle increased from 20 degrees to 40 degrees. During the initiation and persisting throughout the U-turn, the flap amplitude of the right wing (inside of the turn) increased relative to the left wing. In addition, the right wing moved more laterally closer to the centerline of the body during the end of the downstroke and the beginning of the upstroke compared to the left wing. Reorientation of the body into the turn happened prior to a change in the flight path of the bat. Once the bat entered the U-turn and the bank angle increased, the change in flight path of the bat began to change rapidly as the bat negotiated the apex of the turn. During this phase of the turn, the minimum radius of curvature of the bat was 5.5 cm. During the egress of the turn, the bat accelerated and expended stored potential energy by descending. The cycle averaged total power expenditure by the bat during the six wingbeat cycle U-turn maneuver was 0.51 W which was approximately 40% above the power expenditure calculated for a nominally straight flight by the same bat. Future work on the topic of bat maneuverability may investigate a broader array of maneuvering flights characterizing the commonalities and differences across flights. In addition, the interplay between aerodynamic moments and inertial moments are of interest in order to more robustly characterize maneuvering mechanisms.

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Lift enhancement by bats' dynamically changing wingspan

Cited by 41 publications

References 47 publications

Quantifying the dynamic wing morphing of hovering hummingbird

Quantifying the dynamic wing morphing of hovering hummingbird

The Progress of Aerodynamic Mechanisms Based on Avian Leading-Edge Alula and Future Study Recommendations

Analysis of a 180-degree U-turn maneuver executed by a hipposiderid bat

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