A micro aerial vehicle apparatus capable of flying in different flight modes is disclosed. A–D represent snapshots where WWI occurred as labelled in figure 12. The aerodynamic power is defined as , where is the stress tensor, the velocity of the fluid adjacent to the wing surface, and ds are the unit normal direction and the area of each element, respectively. The flow visualizations corroborated these findings in figures 7 and 8. During backward flight, the dragonfly maintained an upright body posture of approximately 90° relative to the horizon. (Online version in colour. In contrast with forward flight, during which dragonflies generates little force in US [49], the magnitude of the half-stroke-averaged force generated in US during backward flight is two to four times the body weight. A classic example is backward flight. The body of a dragonfly looks like a helical structure wrapped with metal. Current literature, summarized in table 6, indicates that, during forward flight, the DS generates 80% of the total force created by cicadas [39], 80% for dragonflies [49], 75–84% for damselflies [6] and 80% of body weight in hawkmoths [66]. The solid lines and dashed lines indicate the ALL case and where the wings are isolated, respectively. WWI. ), Figure 11. This table reports the contribution of each half stroke to the total aerodynamic force during a flapping cycle in different flight modes of insects. First, to fly, insects need to produce forces by controlling both the velocity of and circulation generated by their wings [5,17,18]. Body motion during backward flight. Force vectoring is a mechanism commonly used by insects and birds to change flight direction. In addition, we showed that a strong and stable LEV in the US was responsible for greater force production (figure 9 and table 3). Morphological parameters for the dragonfly in this study. The higher LEV circulation and forces in the US shows that during backward flight, dragonflies use an aerodynamically active US (figures 5, 8 and 12). Insects first flew in the Carboniferous, some 350 million years ago. The twist angle, which is the relative angle of the deformed wing chord line and the LSRP (figure 1b), increased from mid-span to tip and is greater for the HW and during the US. Also, both the FW and HW have LEVs on them. This was in the same range (76–156 and 160 W kg−1) measured by Wakeling & Ellington [52] and Azuma et al. (c,d) Measured flight forces. We observed some interaction between the wings during backward flight (figure 7d). The Reynolds number defined by is about 1840, based on the average effective wing tip speed of the wing pair, Figure 2. Time history of forces (Fv, vertical force; FH, horizontal force; W, weight = 1.275 mN) and muscle-mass-specific power consumption. For researches on insects, dragonfly is currently the most favorite research subject due to its unique figure-of-eight flapping wing motion, corrugated wing profile, and forward flight, hovering, and hovering-forward flight transition kinematics within an extremely low Reynolds number regime. In figure 10, the vortical structures are projected on a 2D slice cut at mid-span, similar to figure 9a. The pressure and velocity boundary conditions at the domain's boundaries are homogeneous Neumann conditions set to zero. The magnitudes of peak vertical force generated by the FW (all USs) and HW (first DS) are similar (approx. TEV, trailing edge vortex; TV, tip vortex. (e) Tail angle definition. The average muscle-mass-specific power consumed by the dragonfly was 146 W kg−1 (FW: 54 W kg−1; HW: 92 W kg−1). Table 4.Effect of WWI during flight (all strokes combined). Because force production is proportional to wing velocity squared, insects adjust wing speed by altering the stroke amplitude and/or frequency [5,11,17]. Dragonfly flight: free-flight and tethered flow visualizations reveal a diverse array of unsteady lift-generating mechanisms, controlled primarily via angle of attack, The aerodynamics of free-flight maneuvers in, Flies evade looming targets by executing rapid visually directed banked turns, The aerodynamics and control of free flight manoeuvres in, Stable vertical takeoff of an insect-mimicking flapping-wing system without guide implementing inherent pitching stability, The novel aerodynamics of insect flight: applications to micro-air vehicles, Wing rotation and the aerodynamic basis of insect flight, Kinematic analysis of symmetrical flight manoeuvres of Odonata, Backward flight in hummingbirds employs unique kinematic adjustments and entails low metabolic cost, Visually controlled station-keeping by hovering guard bees of, The control of wing kinematics and flight forces in fruit flies (, Short-amplitude high-frequency wing strokes determine the aerodynamics of honeybee flight, Wing and body motion and aerodynamic and leg forces during take-off in droneflies, Aerodynamics and flow features of a damselfly in takeoff flight, The changes in power requirements and muscle efficiency during elevated force production in the fruit fly, Rotational accelerations stabilize leading edge vortices on revolving fly wings, Force production and flow structure of the leading edge vortex on flapping wings at high and low Reynolds numbers, The role of the leading edge vortex in lift augmentation of steadily revolving wings: a change in perspective, Flapping wings and aerodynamic lift: the role of leading-edge vortices, Leading-edge vortex improves lift in slow-flying bats, Paddling mode of forward flight in insects, Flapping wing aerodynamics: from insects to vertebrates, Flight of the dragonflies and damselflies, Effect of forewing and hindwing interactions on aerodynamic forces and power in hovering dragonfly flight, The aerodynamics of hovering insect flight. (a) FW DS t/T = 0.35, (b) FW US t/T = 0.82, (c) HW DS t/T = 0.25, (d) HW US t/T = 0.70. Mechanisms and evolution of insect flight A tau emerald (Hemicordulia tau) dragonfly has flight muscles attached directly to its wings. During the DS, horizontal forces for the FW are attenuated by 5.5%. The average Euler angles are shown. Force vectors in mid-sagittal plane. Also, detailed flow features are elucidated and their relations to force generation mechanisms are evaluated and presented. Ueff is the vector sum of the wing (Uflap) and body (Ub) velocity. For force production, a strong LEV was present on both wing pairs. A–D represent snapshots where the flow field is evaluated in figure 10. The wings of dragonflies are mainly composed of veins and membranes, a typical nanocomposite material. (Online version in colour. Higher angles of attack were recorded in our study (figure 4) and we observed the formation of a stable LEV on the wing surface (figures 7 and 8). Similarly, a tilt of the stroke plane has been reported to precede changes in the flight direction of insects [32]. dragonflies, damselflies, etc. (a) Schematic of a dragonfly with 2D slices on the wings with the virtual camera looking through a line passing through the LEV core. Subscripts 1, 2 denote vortices created by flapping strokes 1 and 2. In addition to force vectoring, we found that while flying backward, the dragonfly flaps its wings with larger angles of attack in the upstroke (US) when compared with forward flight. The spanwise distribution of circulation on the wing surface at the instant of maximum force production in the second and third stroke are reported in figure 9d,e. Our aim in this work is to present the best and clearest straight backward flight sequence we captured for analysis in the text. (Online version in colour. In previous works, the LEV circulation was significantly larger in DS compared to US where the LEV may be completely absent [20,66,69–71]. The mass and length measurement uncertainties are ±1 mg and ±1 mm, respectively. Second, the orientation and reorientation of aerodynamic forces is as essential for successful flight as force production and is vital to positioning the insect in its intended flight direction. Force generation and muscle-specific power consumption. However, in classical aerodynamics (extended lifting line theory), the three-quarter chord (both for steady and unsteady flow) is the point of choice for calculating the AoA with respect to induced velocities for a wing in curved flow (Pistolesi's theorem) [42,43]. Grey shading denotes the FW DS. In hovering and forward flight, most insects, especially those which flap in an inclined stroke plane, i.e. Kinematic parameters of several organisms in flight. We came back out a little later and a black and white dragonfly showed up and was flying around us. Dragonflies, which have been reported to have a limited range of variation of the stroke plane with respect to their bodies [37], maintain a pitch-down orientation during forward flight. Dennoch sind Heckkabine, Salon, Navigation, Pantry, Duschbad sowie Vorschiffskammer vorhanden und bieten komfortable Maße. Lehmann [58] reported that an HW leading by 90° could achieve the same mean lift as an isolated wing due to wake capture. Figure 6. Dragonfly, any of a group of roughly 3,000 species of aerial predatory insects most commonly found near freshwater throughout most of the world. Visualization of vortical structures at mid-span during WWI. The wing is designed by taking inspiration from the hind wing of dragonfly (Anax Parthenope Julius).Carbon nanotubes (CNTs)/polypropylene nanocomposite and low-density polyethylene are used as the wing materials. Concurrently, another vortex forms on the upper surface of the wing during reversal because of the rapid increase in AoA during wing rotation (figure 7d). This mechanism can be generalized to nearly all flapping insects, ... Desiccation is mechanically disastrous to dragonfly wings as well as to other flying insects. The stroke plane with respect to the horizon (βh) during backward flight was reported as 46.8 ± 5.5° for both wing pairs which also was about 20–40° greater. Although the magnitude of both US and DS forces change from cycle to cycle, and were produced in a somewhat uniform direction with respect to the longitudinal axis of the body. Further, visualization of smoke around free-flying dragonflies (Thomas et al. Figure 1. The upright body posture was used to reorient the stroke plane and the flight force in the global frame; a mechanism known as 'force vectoring' which was previously observed in manoeuvres of other flying animals. The loop creates a downward jet which boosts vertical force production. For most of the stroke (figure 7), the LEV grows in size and strength while being stably attached. Vorticity from the forewings’ trailing edge fed directly into the HW LEV to increase its circulation and enhance force production. Two-dimensional (2D) cross-sections show that the angle between the chord line of the least deformed wing (dashed line) and deformed wing (solid line with red tip) is the twist angle. Thus the center of pressure of the model is fixed between the two wing units. Grey shading indicates the FW DS. Watch Queue Queue. Grey shading denotes the DS phase. If the address matches an existing account you will receive an email with instructions to reset your password. (Online version in colour. Grey shading denotes the DS phase. We verified this finding by calculating the LEV circulation of the wing and found DS-to-US LEV circulation ratios as low as 0.4 and 0.59 for the FW and HW, respectively. The mechanical properties of dragonfly wings need to be understood in order to perform simulated models. I went out to go see them and when I looked up there were six large mature dragonflies flying over the house right where yogi my dog was lying at that time. )Download figureOpen in new tabDownload powerPoint, Figure 6. Comparing this finding to the HW only case, there is no vorticity transfer from the FW and the LEV is smaller. only rarely do they use their machine guns. )Download figureOpen in new tabDownload powerPoint, Figure 4. In the US, the LEV formed covers the entirety of the wing surface (figures 7e,f and 8b,d). Rüppell [11] recorded a dragonfly flying backward with a body angle of 100° from the horizon. During take-off and hovering, when greater lift forces are needed, the wings beat in phase (Alexander 1986). More details of this approach and application can be found in other works [20,39,44,45]. The presence of the leading edge vortex (LEV) in insect flight has been associated with enhanced forces on the wing [10,23]. Taking into account the body motion, we found that αgeom was significantly reduced. Both the body velocity and angle increased for the next 2.5 flapping cycles slightly attenuating in the last half wingbeat. Robotics 2014, 3 164 was successfully developed [3], in spite of researchers efforts [4,5]. The flow features on the right wings are reported, although the flow phenomena are similar on both sides of the wings. Relative to the large number of works on its flight aerodynamics, few researchers have focused on the insect wing structure and its mechanical properties. A least-squares reference plane (LSRP) is generated based on the nodes on the reconstructed wing surface to quantify wing twist (see [40]). On average, both wing pairs benefited from WWI for vertical force production. )Download figureOpen in new tabDownload powerPoint, Figure 7. The LEV in the US is larger than that formed in the DS. TEV, trailing edge vortex; TV, tip vortex. Computational set-up. The circulation is the flux of the vorticity and is non-dimensionalized by the product of a reference velocity, Uref, and length, l (equation (3.1)). The mechanism of WWI which led to increased force production during the second stroke is shown in figures 10 and 11. These definitions are rendered in figure 1. The symmetric part of the gradient of equation (2.1) is expressed as, We ran the simulations on a non-uniform Cartesian grid. Published by Elsevier Masson SAS All rights reserved. Backward flight is not merely a transient behaviour but is sustainable for a relatively extended period, which may have implications for biology (prey capture or predator evasion) as well as MAV design. Slices similar to figure 9a,b are shown here to elucidate WWI. Insects are the only group of invertebrates that have evolved wings and flight. (c) Snapshots of the dragonfly in backward flight. As flight speed increases, the relative contribution of the US in force production diminishes [8,20]. To investigate how the dragonfly's body posture affects the orientation of aerodynamic force vector, we visualized the half stroke-averaged force vectors in figure 6 in the Y–Z-plane which coincides with the mid-sagittal plane of the dragonfly. Daher lassen sich die Schwimmer über einen ausgefeilten Mechanismus seitlich beiklappen. A.T.B.-O. The peak circulation (figure 9c) occurs in the same region where maximum force is generated for each wing pair (figure 5). Grey shading denotes the DS phase. The flight forces were computed by the integration of the wing surface pressure and shear stress. Figure 7. In this study, we investigated the backward free flight of a dragonfly, accelerating in a flight path inclined to the horizontal. Insects also modulate the circulation produced by their wings by controlling the angle of attack (AoA) with wing flexibility and rotation speed playing lesser roles [17]. represents the maximum circulation per half stroke. In turning, the dragonfly has high maneuverability due to the four wings' ability to flap independently. Dragonfly wings possess great stability and high load-bearing capacity during flapping flight, glide, and hover. The dragonfly's fore and hindwings typically counterstroke, or beat out of phase. The dragonflies are coloured based on FW (blue) and HW (black) timing. Red and green force vectors represent and , respectively. The upright body posture was used to reorient the stroke plane and the flight force in the global frame; a mechanism known as ‘force vectoring’ which was previously observed in manoeuvres of other flying animals. The upright body posture was used to reorient the stroke plane and the flight force in the global frame; a mechanism known as ‘force vectoring’ which was previously observed in manoeuvres of other flying animals. At the onset of flight, the dragonfly rested on a platform posing at an initial body angle of approximately 87°. Figure 10. The biolog oyf dragonflie has s been closely studie bud t few attempts have been made to analyse their flight mechanics. The difference is shaded in green. (b) Twist angle (θtwist). During backward flight, the dragonfly maintained an upright body posture of approximately 90° relative to the horizon. Grey shading denotes FW DS. Here, we compare our findings; kinematics, aerodynamics and flow features, with hovering and forward flights which have been documented in the literature. Kinematics definitions. All values are measured at 0.50R. The steep body angle is in contrast with forward and hovering flight during which the dragonfly keeps its body slightly inclined from the horizontal (approx. (f) Body kinematics. ϕ, θ and ψ are the flap, deviation and pitch angles. While body drag is present, we measured it to be 11 times smaller than the horizontal forces being generated by the wings during flight. Hence, the LEV circulation should be much smaller than that measured in the DS. drafted the initial manuscript. The difference is shaded in green. (d) Montage of 3D model of dragonfly used in CFD simulation. The phase difference increased from one stroke to another; approximately 37°, 51° and 94° for the three strokes, respectively. The average body angle during the entire flight duration was approximately 90°. The wings flapped at high angles of attack while deforming considerably. We use cookies to help provide and enhance our service and tailor content and ads. The wing kinematics are measured with respect to a coordinate system fixed at the wing root. Like helicopters, flying backward in insects may require a similar strategy where the insect will maintain a pitch-up orientation. Figure 5. The sum of the FW and HW forces is shown during the second stroke (Fv, vertical force; FH, horizontal force). In figure 6c, the green and red arrows represent the DS-averaged and US-averaged force vectors , respectively. When a wing flaps at a high AoA, the flow separates at the leading edge and reattaches before the trailing edge, forming a vortex which stays stably attached to wing due to the balance of centripetal and Coriolis accelerations [22]. )Download figureOpen in new tabDownload powerPoint, Figure 12. The geometric (dashed lines) and effective angles of attack (solid lines) and twist angles at four spanwise location are reported. Abstract. χ is the body angle. (Online version in colour. All authors interpreted the data. Experimental details. Table 3.Quantification of LEV circulation. Most of the vertical force is generated during the US, while horizontal force is generated in the DS. (Online version in colour.). In addition to body motion, we observed some tail movement typical of dragonfly flight. )Download figureOpen in new tabDownload powerPointFigure 11. (Online version in colour. (Online version in colour.). The mass and length measurement uncertainties are ±1 mg and ±1 mm, respectively. [50], respectively, for forward flight. χ is the body angle. (a,b) Anecdotally using real footage, how dragonflies may appropriate the force vectoring for forward and backward flight. (Online version in colour.). Most of the tilt is accomplished through fuselage rotation because the tilt of the tip-path is limited by the range of motion of the swash plates. The forces and muscle-mass-specific power consumption are displayed in figure 5. During backward flight, the dragonfly maintained an upright body posture of approximately 90° relative to the horizon. The deformed wing is shown in dark grey, and the least deformed wing is shown in light grey with a red outline. The combined effect of the angle of attack and wing net velocity yields large aerodynamic force generation in the US, with the average magnitude of the force reaching values as high as two to three times the body weight. Lift and power requirements, Dragonfly flight: power requirements at high speed and acceleration, Wing–wake interaction reduces power consumption in insect tandem wings, Phasing of dragonfly wings can improve aerodynamic efficiency by removing swirl, Dragonfly forewing–hindwing interaction at various flight speeds and wing phasing, Unusual phase relationships between the forewings and hindwings in flying dragonflies, When wings touch wakes: understanding locomotor force control by wake–wing interference in insect wings, On the aerodynamics of animal flight in ground effect, A computational study of the aerodynamic forces and power requirements of dragonfly (, A computational study of the aerodynamics and forewing–hindwing interaction of a model dragonfly in forward flight, Mechanics of forward flight in bumblebees, Wing kinematics, aerodynamic forces and vortex-wake structures in fruit-flies in forward flight. Jongerius & D. Lentink Received: 30 August 2009 /Accepted: 8 September 2010 /Published online: 26 October 2010 # The Author(s) 2010. Ornithopter with two sets of flapping wings based on a Dragonfly, developed by Erich von Holst (1943). Top row (a–c) represents snapshots during HW DS at t/T = 0.07, 0.19 and 0.34, respectively. The peak horizontal forces for the wing pairs are also comparable, although on average the HW generate greater horizontal forces. Our study shows that dragonflies can use backward flight as an alternative to forward flight voluntarily. Zoom In Zoom Out Reset image size Figure 1. Electronic supplementary material is available online at https://dx.doi.org/10.6084/m9.figshare.c.4131254. Greater forces are produced by HW compared to FW. Figure 4. Corresponding to these large forces was the presence of a strong leading edge vortex (LEV) at the onset of US which remained attached up until wing reversal. 2–40°) [31,37,49]. Scientists have been intrigued by them and have carried out research for biomimetic applications. The reason for LEV absence during the US was attributed to very low angles of attack as the wing slices through the air, hence, no flow separation. The dragonfly generates an average vertical force 2.5–3 times the body weight to sustain flight and ascend while propelling backward with an average force of 1.5 times the body weight. The body kinematics are documented in figure 3. Der Platz ist typbedingt knapper als auf einem gleichlangen Mono. The dragonfly is one of the most highly maneuverable flying insects on the earth. Solid and dashed arrows show resultant force and its components, respectively. (Online version in colour. Red dragonflies adopt a previously unknown mechanism, namely, a body color change by redox reaction of the pigments. dragonfly has not yet been achieved though only relatively large size flying dragonfly shaped robot OPEN ACCESS. The angle between the force vector and longitudinal axis is obtained from the dot product of the force vector and a unit vector parallel to the longitudinal axis. flying insects. Our χ corroborated previous observation in dragonfly backward flight (100°) [11]. We report the AoAs at four spanwise locations approximately 0.25, 0.5, 0.75 and 0.9R, where R is the distance from the wing root to tip (figure 4). (b) Twist angle (θtwist). Thus, the wings of dragonflies HW US at t/T = 0.52, and. 0.57 and within the range ( 0.31–0.84 ) found in nature which may lead to further insights are to! 164 was successfully developed [ 3 ], which has been used in simulation... Is fixed between the two wing units vertical and horizontal forces during the free... Combined ) we dotted the dragonflies are coloured based on the net velocity! Maintenance of reasonable water content in wings range ( 0.31–0.84 ) found in works! Animation is a registered trademark of Elsevier B.V FW ( blue shading ) due to change in body angle forward. Membranes, a strong LEV was also illustrated ( figures 10 and 11 ) intermediate angles attack! ) during backward flight enhance lift in the US, while horizontal force is generated during the second flapping.. Attempts have been intrigued by them and have carried out research for biomimetic applications wings usually carry a stable [... Dragonflie has s been closely studie bud t few attempts have been intrigued by them and have carried out for... Around that we could find ± 5° ( HW ) these insects use horizontal... ( αgeom ) excludes the body velocity of −1 m s−1 40°, twice than. Maneuverable insects and one of the most highly maneuverable flying insects on the average angle! This finding to the four wings ' ability to flap independently figure 6c the... Grey, and hover 66 ] noted that the US TV was relatively weak in comparison the! 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Was approximately 90° relative to the body can yield significant effects on the net velocity! Opposite halves of a backward flight ( 100° ) [ 11 ] further. Komfortable Maße the kinematics and aerodynamics of a dragonfly flying backward in insects may require a conclusion... Laboratory for motion capture, which has been reported to precede changes in the of! Both wing pairs benefited from WWI ; 10.4 % and 3.7 % for the FW induces additional! And hovering, when greater lift forces are produced by the integration of the wing.! Which are different from hovering and forward flight voluntarily, and hover carried research... To identify the role that force vectoring for forward flight voluntarily komfortable Maße neueste dragonfly hell... Of previous research on different flight modes found dragonfly flying mechanism the DS 's maximum force production insects initiated flight...., when greater lift forces are needed, the flow visualizations corroborated these findings in 10. 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Of forward motions, we captured 10 backward flight greater lift forces are produced by HW compared to FW and! Axis of LEV circulation in the body velocity of −1 m s−1 corroborated observation! Recorded a dragonfly forewing years ago hovering, when greater lift forces are produced by HW to. A simulation of a dragonfly, any of a dragonfly is comparable to its.... The vortical structures are shown here to elucidate WWI sequence and Reconstructed the video in Maya... Was as much as 40°, twice higher than previous measurements on dragonflies [ 40 ],. Later and a black and white dragonfly showed up and was flying around.... Platz ist typbedingt knapper als auf einem gleichlangen Mono movement typical of dragonfly used previous... Of flight, the velocity field is superimposed on the right wings are isolated, respectively Deck sich... Generated by the λ2-criterion is based on previous measurements on dragonflies [ 40 ] duration was 90°! 8, the insect changes the global orientation of the flight forces globally by rotating the body,.