Flapping flight is a commonly used mechanism of micro aerial vehicles and insects alike.
Dragonflies use their four-winged anatomy to navigate the environment, maneuver
around obstacles, and perform other essential flight patterns. The flight performance and
aerodynamics of intact flapping wings is well known; however, this study aims to clarify
how wing damage affects the flight performance. First, high speed videos of the damaged
wing flight, a takeoff performed by a dragonfly, is captured, and subsequently digitally
reconstructed to create a three-dimensional model. Second, using an immersed-boundary
method (IBM) based incompressible Navier-Stokes direct numerical simulation (DNS)
solver, we resolve the aerodynamic forces and wake topology of the dragonfly’s damaged
wing flapping flight in high detail. We found that spanwise damage doesn’t cause any
detriment to the force capabilities of the damaged wing which is due to increased pitch
angles of the damaged wing. As a consequence, fliers with spanwise damaged and intact
wings may be able to utilize similar strategies to achieve takeoffs. The wake topology of
the wing damaged flight is also examined. This work serves as a baseline for studying the
effect of wing damage for flapping flight and could provide useful insights to micro-aerial
vehicle (MAV) designers as some degree of wing damage may be an inevitable occurrence
for winged fliers.
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Roll Maneuverability of Flapping Flight Winged Systems
The goal of this paper is to study the effect of wing flapping kinematics on roll maneuverability of flapping flight systems. Inspired from birds maneuvering action, we study the effect of asymmetric flapping angular velocities of the wings on generating roll motions on the body. To expand the generality of the results, the equations of motion are written dimensionless. The effect of aerodynamic parameter, forward velocity and wing inertia are presented. The results show that applying asymmetric velocities during flight is useful for relatively larger wings.
more » « less- Award ID(s):
- 1931122
- NSF-PAR ID:
- 10299352
- Date Published:
- Journal Name:
- ASME 2020 Dynamic Systems and Control Conference
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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Flapping wings of insects serve for both generating aerodynamic forces and enhancing olfactory sensitivities when navigating on the odor-rich planet. Despite the extensive investigations of the aerodynamic function of flapping wings, we have limited understanding of how the flapping wings potentially affect the physiological sensitivities during flight. In this paper, direct numerical simulations were used to investigate a fruit fly model in an upwind surging motion. The wing pitch kinematics were prescribed using a hyperbolic function, which can change the wing pitch profile from a sinusoidal function to a step function by adjusting the “C” factor in the hyperbolic function. Both aerodynamic performance and olfactory detections were quantified at various wing pitch kinematics patterns. The effects of flapping wings on the odor transport were visualized using the Lagrangian approach by uniformly releasing passive odor tracers in upstream. The study revealed that the insect had the potential to achieve higher aerodynamic performance by tailoring wing pitch kinematics, but it could reduce the odor mass flux around the antenna. It was suspected that the natural flyers might sacrifice certain aerodynamic potential to enhance their olfactory sensitivity for surviving purposes. In addition, a trap-and-flick mechanism is proposed here during the supination phase in order to enhance the olfactory sensitivity. Similar to the clip-and-fling mechanism for enhancing the force generation during the pronation phase, the newly proposed trap-and-flick mechanism is also due to the wing-wing interaction in flapping flight. These findings could provide important implications for engineering applications of odor-guided flapping flight.
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Abstract Insects rely on their olfactory system to forage, prey, and mate. They can sense odorant plumes emitted from sources of their interests with their bilateral odorant antennae, and track down odor sources using their highly efficient flapping-wing mechanism. The odor-tracking process typically consists of two distinct behaviors: surging upwind at higher velocity and zigzagging crosswind at lower velocity. Despite extensive numerical and experimental studies on odor guided flight in insects, we have limited understandings on the effects of flight velocity on odor plume structure and its associated odor perception. In this study, a fully coupled three-way numerical solver is developed, which solves the 3D Navier-Stokes equations coupled with equations of motion for the passive flapping wings, and the odorant convection-diffusion equation. This numerical solver is applied to resolve the unsteady flow field and the odor plume transport for a fruit fly model at different flight velocities in terms of reduced frequency. Our results show that the odor plume structure and intensity are strong related to reduced frequency. At smaller reduced frequency (larger forward velocity), odor plume is pushed up during downstroke and draw back during upstroke. At larger reduced frequency (smaller forward velocity), the flapping wings induce a shield-like air flow around the antennae which may greatly increase the odor sampling range. Our finding may explain why flight velocity is important in odor guided flight.
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Abstract Flapping flight of animals has captured the interest of researchers due to their impressive flight capabilities across diverse environments including mountains, oceans, forests, and urban areas. Despite the significant progress made in understanding flapping flight, high-altitude flight as showcased by many migrating animals remains underexplored. At high-altitudes, air density is low, and it is challenging to produce lift. Here we demonstrate a first lift-off of a flapping wing robot in a low-density environment through wing size and motion scaling. Force measurements showed that the lift remained high at 0.14 N despite a 66% reduction of air density from the sea-level condition. The flapping amplitude increased from 148 to 233 degrees, while the pitch amplitude remained nearly constant at 38.2 degrees. The combined effect is that the flapping-wing robot benefited from the angle of attack that is characteristic of flying animals. Our results suggest that it is not a simple increase in the flapping frequency, but a coordinated increase in the wing size and reduction in flapping frequency enables the flight in lower density condition. The key mechanism is to preserve the passive rotations due to wing deformation, confirmed by a bioinspired scaling relationship. Our results highlight the feasibility of flight under a low-density, high-altitude environment due to leveraging unsteady aerodynamic mechanisms unique to flapping wings. We anticipate our experimental demonstration to be a starting point for more sophisticated flapping wing models and robots for autonomous multi-altitude sensing. Furthermore, it is a preliminary step towards flapping wing flight in the ultra-low density Martian atmosphere.more » « less
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Abstract Flapping, flexible wings deform under both aerodynamic and inertial loads. However, the fluid-structure interaction (FSI) governing flapping wing dynamics is not well understood. Conventional FSI models require excessive computational resources and are not conducive to parameter studies that consider variable wing kinematics or geometry. Here, we present a simple two-way coupled FSI model for a wing subjected to single-degree-of-freedom (SDOF) rotation. The model is reduced-order and can be solved several orders of magnitude faster than direct computational methods. We construct a SDOF rotation stage and measure basal strain of a flapping wing in-air and in-vacuum to study our model experimentally. Overall, agreement between theory and experiment is excellent. In-vacuum, the wing has a large 3ω response when flapping at approximately 1/3 its natural frequency. This response is attenuated substantially when flapping in-air as a result of aerodynamic damping. These results highlight the importance of two-way coupling between the fluid and structure, since one-way coupled approaches cannot describe such phenomena. Moving forward, our model enables advanced studies of biological flight and facilitates bio-inspired design of flapping wing technologies.
- Free Publicly Accessible Full Text
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Accepted Manuscript1.0
- Conference Paper:
- https://doi.org/10.1115/DSCC2020-3309
