| 1. |
- Bomphrey, Richard J., et al.
(författare)
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Flight of the dragonflies and damselflies
- 2016
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Ingår i: Philosophical Transactions of the Royal Society B: Biological Sciences. - : The Royal Society. - 0962-8436 .- 1471-2970. ; 371:1704
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Tidskriftsartikel (refereegranskat)abstract
- This work is a synthesis of our current understanding of the mechanics, aerodynamics and visuallymediated control of dragonfly and damselfly flight, with the addition of new experimental and computational data in several key areas. These are: the diversity of dragonfly wing morphologies, the aerodynamics of gliding flight, force generation in flapping flight, aerodynamic efficiency, comparative flight performance and pursuit strategies during predatory and territorial flights. Newdata are set in context by brief reviews covering anatomy at several scales, insect aerodynamics, neuromechanics and behaviour. We achieve a new perspective by means of a diverse range of techniques, including laser-line mapping of wing topographies, computational fluid dynamics simulations of finely detailed wing geometries, quantitative imaging using particle image velocimetry of on-wing and wake flow patterns, classical aerodynamic theory, photography in the field, infrared motion capture and multi-camera optical tracking of free flight trajectories in laboratory environments. Our comprehensive approach enables a novel synthesis of datasets and subfields that integrates many aspects of flight from the neurobiology of the compound eye, through the aeromechanical interface with the surrounding fluid, to flight performance under cruising and higher-energy behavioural modes.
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| 2. |
- Henningsson, Per, et al.
(författare)
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Efficiency of Lift Production in Flapping and Gliding Flight of Swifts
- 2014
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Ingår i: PLoS ONE. - : Public Library of Science (PLoS). - 1932-6203. ; 9:2
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Tidskriftsartikel (refereegranskat)abstract
- Many flying animals use both flapping and gliding flight as part of their routine behaviour. These two kinematic patterns impose conflicting requirements on wing design for aerodynamic efficiency and, in the absence of extreme morphing, wings cannot be optimised for both flight modes. In gliding flight, the wing experiences uniform incident flow and the optimal shape is a high aspect ratio wing with an elliptical planform. In flapping flight, on the other hand, the wing tip travels faster than the root, creating a spanwise velocity gradient. To compensate, the optimal wing shape should taper towards the tip (reducing the local chord) and/or twist from root to tip (reducing local angle of attack). We hypothesised that, if a bird is limited in its ability to morph its wings and adapt its wing shape to suit both flight modes, then a preference towards flapping flight optimization will be expected since this is the most energetically demanding flight mode. We tested this by studying a well-known flap-gliding species, the common swift, by measuring the wakes generated by two birds, one in gliding and one in flapping flight in a wind tunnel. We calculated span efficiency, the efficiency of lift production, and found that the flapping swift had consistently higher span efficiency than the gliding swift. This supports our hypothesis and suggests that even though swifts have been shown previously to increase their lift-to-drag ratio substantially when gliding, the wing morphology is tuned to be more aerodynamically efficient in generating lift during flapping. Since body drag can be assumed to be similar for both flapping and gliding, it follows that the higher total drag in flapping flight compared with gliding flight is primarily a consequence of an increase in wing profile drag due to the flapping motion, exceeding the reduction in induced drag.
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| 3. |
- Henningsson, Per, et al.
(författare)
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The complex aerodynamic footprint of desert locusts revealed by large-volume tomographic particle image velocimetry.
- 2015
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Ingår i: Journal of the Royal Society Interface. - : The Royal Society. - 1742-5662 .- 1742-5689. ; 12:108
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Tidskriftsartikel (refereegranskat)abstract
- Particle image velocimetry has been the preferred experimental technique with which to study the aerodynamics of animal flight for over a decade. In that time, hardware has become more accessible and the software has progressed from the acquisition of planes through the flow field to the reconstruction of small volumetric measurements. Until now, it has not been possible to capture large volumes that incorporate the full wavelength of the aerodynamic track left behind during a complete wingbeat cycle. Here, we use a unique apparatus to acquire the first instantaneous wake volume of a flying animal's entire wingbeat. We confirm the presence of wake deformation behind desert locusts and quantify the effect of that deformation on estimates of aerodynamic force and the efficiency of lift generation. We present previously undescribed vortex wake phenomena, including entrainment around the wing-tip vortices of a set of secondary vortices borne of Kelvin-Helmholtz instability in the shear layer behind the flapping wings.
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| 4. |
- Horstmann, Jan T, et al.
(författare)
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Wake Development behind Paired Wings with Tip and Root Trailing Vortices: Consequences for Animal Flight Force Estimates.
- 2014
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Ingår i: PLoS ONE. - : Public Library of Science (PLoS). - 1932-6203. ; 9:3
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Tidskriftsartikel (refereegranskat)abstract
- Recent experiments on flapping flight in animals have shown that a variety of unrelated species shed a wake behind left and right wings consisting of both tip and root vortices. Here we present an investigation using Particle Image Velocimetry (PIV) of the behaviour and interaction of trailing vortices shed by paired, fixed wings that simplify and mimic the wake of a flying animal with a non-lifting body. We measured flow velocities at five positions downstream of two adjacent NACA 0012 aerofoils and systematically varied aspect ratio, the gap between the wings (corresponding to the width of a non-lifting body), angle of attack, and the Reynolds number. The range of aspect ratios and Reynolds number where chosen to be relevant to natural fliers and swimmers, and insect flight in particular. We show that the wake behind the paired wings deformed as a consequence of the induced flow distribution such that the wingtip vortices convected downwards while the root vortices twist around each other. Vortex interaction and wake deformation became more pronounced further downstream of the wing, so the positioning of PIV measurement planes in experiments on flying animals has an important effect on subsequent force estimates due to rotating induced flow vectors. Wake deformation was most severe behind wings with lower aspect ratios and when the distance between the wings was small, suggesting that animals that match this description constitute high-risk groups in terms of measurement error. Our results, therefore, have significant implications for experimental design where wake measurements are used to estimate forces generated in animal flight. In particular, the downstream distance of the measurement plane should be minimised, notwithstanding the animal welfare constraints when measuring the wake behind flying animals.
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| 5. |
- Nakata, Toshiyuki, et al.
(författare)
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Recent progress on the flight of dragonflies and damselflies
- 2020
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Ingår i: International Journal of Odonatology. - : Worldwide Dragonfly Association. - 1388-7890 .- 2159-6719. ; 23:1, s. 41-49
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Tidskriftsartikel (refereegranskat)abstract
- Remarkable flight performance is key to the survival of adult Odonata. They integrate varied three-dimensional architectures and kinematics of the wings, unsteady aerodynamics, and sensory feedback control in order to achieve agile flight. Therefore, a diverse range of approaches are necessary to understand their flight strategy comprehensively. Recently, new data have been presented in several key areas in Odonata such as measurement of surface topographies, computational fluid dynamic analyses, quantitative flow visualisation using particle image velocimetry, and optical tracking of free flight trajectories in laboratory environments. In this paper, we briefly review those findings alongside more recent studies that have advanced our understanding of the flight mechanics of Odonata still further.
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| 6. |
- Ray, Robert P, et al.
(författare)
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Enhanced flight performance by genetic manipulation of wing shape in Drosophila.
- 2016
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Ingår i: Nature Communications. - : Springer Science and Business Media LLC. - 2041-1723. ; 7
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Tidskriftsartikel (refereegranskat)abstract
- Insect wing shapes are remarkably diverse and the combination of shape and kinematics determines both aerial capabilities and power requirements. However, the contribution of any specific morphological feature to performance is not known. Using targeted RNA interference to modify wing shape far beyond the natural variation found within the population of a single species, we show a direct effect on flight performance that can be explained by physical modelling of the novel wing geometry. Our data show that altering the expression of a single gene can significantly enhance aerial agility and that the Drosophila wing shape is not, therefore, optimized for certain flight performance characteristics that are known to be important. Our technique points in a new direction for experiments on the evolution of performance specialities in animals.
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