In addition to body motion, we observed some tail movement typical of dragonfly flight. A least-squares reference plane (LSRP) is generated based on the nodes on the reconstructed wing surface to quantify wing twist (see [40]). Top row (a–c) represents snapshots during HW DS at t/T = 0.07, 0.19 and 0.34, respectively. The wing kinematics are measured with respect to a coordinate system fixed at the wing root. Honeybees [18], drone flies [19], damselflies [20] and fruit flies [21] all increase stroke amplitude to generate larger flight forces. The blood circulation is essential for the maintenance of reasonable water content in wings. The body of a dragonfly looks like a helical structure wrapped with metal. Our measured CD was 0.57 and within the range (0.31–0.84) found in the literature [53,68]. Dragonflies can hover fly, at high speed and manoeuvre skilfull iyn the air in order to defend their territory, feed on live prey and mat in tandee m formation. ), Figure 8. Daher lassen sich die Schwimmer über einen ausgefeilten Mechanismus seitlich beiklappen. While body drag is present, we measured it to be 11 times smaller than the horizontal forces being generated by the wings during flight. 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. )Download figureOpen in new tabDownload powerPoint, Figure 7. Flow features at maximum force production during second stroke for each wing pair. Visualization of vortical structures at mid-span during WWI. (a) Reconstructed dragonfly (ii) overlapped on a real image (i). Currently, the variation of forces on a half-stroke basis and the roles of the US and DS in force generation during backward flight are less understood. )Download figureOpen in new tabDownload powerPoint, Figure 10. The LEV in the US is larger than that formed in the DS. TEV, trailing edge vortex; TV, tip vortex. )Download figureOpen in new tabDownload powerPoint, Figure 6. Solid and dashed arrows show resultant force and its components, respectively. (Online version in colour. From their smoke visualization and analysis, there was no hint of an LEV to enhance lift in the US. The DS-to-US duration ratio changed on a stroke-by-stroke basis from 0.9 (first stroke) to 0.7 (second stroke) to 1 (third stroke) for the FW and from 0.9 (first stroke) to 0.8 (second and third strokes) for the HW. αeff and αgeom are the effective and geometric angles of attack. The geometric AoA (αgeom) excludes the body velocity. 26, 28, 29, 55, 56, 57 Researches on flies, 29, 58 bees, 29, 58, 59, 60 hoverflies, 61, 62, 63 wasps, 29 locusts, 29, … During this time he worked on developing a flying robot that employed the principles of the dragonfly's mechanisms of flight. All rights reserved. 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. Although there are different views on how the existence and attachment of the LEV contribute to force production in insect flight (absence of stall [24], increasing wing circulation/suction [25], etc. therefore they rely on speed, intelligence, and maneuverability. A dragonfly is an insect belonging to the order Odonata, infraorder Anisoptera (from Greek ἄνισος anisos, "unequal" and πτερόν pteron, "wing", because the hindwing is broader than the forewing).Adult dragonflies are characterized by large, multifaceted eyes, two pairs of strong, transparent wings, sometimes with coloured patches, and an elongated body. In figure 11, the velocity field is superimposed on the vorticity contours in a zoomed in a snapshot of figure 10a. Vortex development in backward flight. [38] reported that a stroke plane tilted backward, and a steep body angle between 50° and 70° from the horizontal induced backward flight in waterlily beetles (Galerucella nymphaeae). The loop creates a downward jet which boosts vertical force production. At the onset of flight, the dragonfly rested on a platform posing at an initial body angle of approximately 87°. 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. 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. First, to fly, insects need to produce forces by controlling both the velocity of and circulation generated by their wings [5,17,18]. The reconstruction process captured both the kinematics and deformations. 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. All values are measured at 0.50R. While many of the flight sequences were of forward motions, we captured 10 backward flight videos. It is not certain whether by maintaining a high body angle, dragonflies will drastically increase body drag because they possess slender bodies. )Download figureOpen in new tabDownload powerPoint, Figure 1. A–D represent snapshots where the flow field is evaluated in figure 10. Both wing pairs generate larger forces in US compared to DS. The domain size was totalling 14 million grids. )Download figureOpen in new tabDownload powerPoint, Figure 12. Grey shading denotes the DS phase. 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]. The veins and membranes have a complex design within the wing that give rise to whole-wing characteristics which result in dragonflies being supremely versatile, maneuverable fliers. A classic example is backward flight. The wings flapped at high angles of attack while deforming considerably. [1] also arrived at a similar conclusion with smoke visualizations on dragonflies in tethered and free forward light. ScienceDirect ® is a registered trademark of Elsevier B.V. ScienceDirect ® is a registered trademark of Elsevier B.V. Robotics 2014, 3 164 was successfully developed [3], in spite of researchers efforts [4,5]. The bottom row (d–f) represents snapshots during HW US at t/T = 0.52, 0.70 and 0.87, respectively. Since the flight forces are a strong function of wing kinematics, generated flight forces vary drastically during flight because the kinematics of the upstroke (US) and downstroke (DS) can be utterly different [3,20,31]. 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. Thus the center of pressure of the model is fixed between the two wing units. On average, both wing pairs benefited from WWI for vertical force production. The deformed wing is shown in dark grey, and the least deformed wing is shown in light grey with a red outline. (a,b) Anecdotally using real footage, how dragonflies may appropriate the force vectoring for forward and backward flight. These changes influence both (i) the production and (ii) orientation and reorientation of aerodynamic forces, consequently determining the type of free flight manoeuvre that is performed. 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. 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]. Wing kinematics and twist. χ is the body angle. During backward flight, the dragonfly wings swept through a stoke plane (βb) inclined at 35 ± 5°; an angle shallower than βb of dragonflies of similar mass and morphology in forward flight by 15° [37,50]. By continuing you agree to the use of cookies. Table 3.Quantification of LEV circulation. There was around 10 flying around that we could find. Our χ corroborated previous observation in dragonfly backward flight (100°) [11]. Likewise, Mukundarajan et al. (Online version in colour. Greater forces are produced by HW compared to FW. The pressure and velocity boundary conditions at the domain's boundaries are homogeneous Neumann conditions set to zero. 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]. Whereas in figure 8, the flow structures are shown during maximum force production. Kinematics definitions. The presence of the leading edge vortex (LEV) in insect flight has been associated with enhanced forces on the wing [10,23]. The advance ratio (J), defined as the ratio of the average body to wingtip velocity is −0.31 ± 0.12. During the mid-US and at maximum force production, the HW flow consists of an LEV, TV and a trailing edge vortex (TEV) connected to form a vortex loop (figures 7e and 8d). Previous insect flight studies have measured the AoA at locations between the leading edge and quarter-chord or near the rotation axis of the wing [19,41]. The Reynolds number defined by is about 1840, based on the average effective wing tip speed of the wing pair, Figure 2. (Online version in colour.). 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). (c) Snapshots of the dragonfly in backward flight. Flow visualization and unsteady aerodynamics in the flight of the hawkmoth, Smart wing rotation and trailing-edge vortices enable high frequency mosquito flight, Dragonfly 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. Zoom In Zoom Out Reset image size Figure 1. Scientists have been intrigued by them and have carried out research for biomimetic applications. (d) Montage of 3D model of dragonfly used in CFD simulation. Visualization of vortical structures at mid-span during WWI. This influx is absent in the HW only case, leading to the formation of a weaker LEV and consequently, a weaker jet below the wing (figure 11b). This mechanism can be generalized to nearly all flapping insects, ... Desiccation is mechanically disastrous to dragonfly wings as well as to other flying insects. LEV circulation. Body motion during backward flight. Also, the LEV circulation in the US is greater than the DS's. Vorticity from the forewings’ trailing edge fed directly into the HW LEV to increase its circulation and enhance force production. (Online version in colour. Wang & Sun [62], using CFD, verified the absence of the LEV in the US in hovering as well as forward flight of dragonflies. 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. During backward flight, the dragonfly maintained an upright body posture of approximately 90° relative to the horizon. The AoA decreased from root to tip. In figure 7, we present the evolution of the wake structures during the second stroke based on the HW timing. It can achieve speeds up to 55 km/h, turn 360° in microseconds, fly sideways, glide, hover in the air and even go backwards. represents the maximum circulation per half stroke. We declare we have no competing interests. The centre of mass of the body was elevated by about during the last two flapping cycles with most of the body motion occurring in the horizontal direction . The morphological parameters of the selected dragonfly are shown in table 1, and the flight video can be found in the electronic supplementary material. https://doi.org/10.1016/j.crme.2011.11.003. The wings of dragonflies are mainly composed of veins and membranes, a typical nanocomposite material. The TV is also more pronounced and suggests that the strength of the LEV feeding it may be greater than the DS's. Force vectors in mid-sagittal plane. (Online version in colour. However, χ was significantly larger than those of hummingbirds (50–75°) which use a horizontal stroke plane and waterlily beetles (50–70°), which use an inclined stroke plane [13,38]. III. Funding support from National Science Foundation (CBET-1313217) and Air Force Office of Scientific Research (FA9550-12-1-007). The peak horizontal forces for the wing pairs are also comparable, although on average the HW generate greater horizontal forces. Table 2.Forces from three different grids set-up. I love dragonflies and after loosing my father I was at a friends place a couple hours after I was told he had passed… I had a huge dragonfly hanging around where i was sitting that morning, a few months latter in the early hours (1.30am) at a new years party i had another appear and … In addition to the rigid wing kinematics, the wing twist is reported in figure 4. The vortex structures are visualized by the λ2-criterion [47], which has been used in previous insect flight studies [44,48]. III. The mechanism of WWI was also illustrated (figures 10 and 11). The prototype of the mechanism, built at a scale of four times the size of a dragonfly having a wingspan of 150 mm, is able to create motions in the wing of flapping and feathering, and can vary the stroke plane. (a) Computational mesh employed in the study. We dotted the dragonflies' wings for tracking purposes and placed the insects in a filming area. Previous studies have indicated that the FW experience in-wash due to the HW and the HW are affected by the downwash from the FW with benefits being dependent on the phase difference between wing pairs [31,54–57]. only rarely do they use their machine guns. (Online version in colour.). Like helicopters, flying backward in insects may require a similar strategy where the insect will maintain a pitch-up orientation. All the DS-to-US LEV circulation ratios are less than unity (table 3). (a) Reconstructed dragonfly (ii) overlapped on a real image (i). We selected one flight sequence and reconstructed the video in Autodesk Maya (Autodesk Inc.). The apparatus includes a fuselage; at least one pair of blade-wings; and an actuator for actuating the blade-wings by flapping the blade-wings in dissonance or resonance frequencies. (f) Body kinematics. For force production, a strong LEV was present on both wing pairs. Comparing this finding to the HW only case, there is no vorticity transfer from the FW and the LEV is smaller. Relative to the large number of works on its flight aerodynamics, few researchers have focused on the insect wing structure and its mechanical properties. 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]. Kinematics definitions. Figure 4. Experiments on hovering kinematics showed that both wing pairs generate maximum lift when the HW lead by a quarter of the cycle and the distance between the wings is closest [54]. Figure 10. Kinematics, The kinematics an daerodynamics of the free flight of some Diptera, Kinematics of slow turn maneuvering in the fruit bat, Pigeons steer like helicopters and generate down- and upstroke lift during low speed turns, Dragonfly flight. (b) Grid-independent study. The mechanical properties of dragonfly wings need to be understood in order to perform simulated models. 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. In hovering and forward flight, most insects, especially those which flap in an inclined stroke plane, i.e. (d,e) Spanwise distribution of LEV circulation at maximum force production during the second and third stroke, respectively. 2004) indicates the potential for a range of wing–wake interactions in forward flight. The insect left the platform smoothly while increasingly leaning backward. A micro aerial vehicle apparatus capable of flying in different flight modes is disclosed. 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). In the polar plot, black vectors clustered around 90° indicate the body longitudinal axis. This table reports the contribution of each half stroke to the total aerodynamic force during a flapping cycle in different flight modes of insects. Grey shading denotes the FW DS. Chapter 2 gives a deeper look on what makes a dragonfly fly, existing flying robots, flapping mechanism, and … The LEV was also present in both half strokes with the US LEV being stronger. We use cookies to help provide and enhance our service and tailor content and ads. Time history of forces (Fv, vertical force; FH, horizontal force; W, weight = 1.275 mN) and muscle-mass-specific power consumption. In this study, we investigated the backward free flight of a dragonfly, accelerating in a flight path inclined to the horizontal. 2–40°) [31,37,49]. However, the change in magnitude of the force, as well as production of large aerodynamic forces in US, cannot be explained by force vectoring alone. Figure 12. Grey shading denotes the FW DS. Electronic supplementary material is available online at https://dx.doi.org/10.6084/m9.figshare.c.4131254. Gilles Martin, a nature photographer, has done a two-year study examining dragonflies, and he also concluded that these creatures have an extremely complex flight mechanism. (a,b) Anecdotally using real footage, how dragonflies may appropriate the force vectoring for forward and backward flight. Mechanisms and evolution of insect flight A tau emerald (Hemicordulia tau) dragonfly has flight muscles attached directly to its wings. The average body angle during the entire flight duration was approximately 90°. During the US, both pairs of wings profited from WWI; 10.4% and 3.7% for the FW and HW, respectively. 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. A more detailed study of the 3D reconstruction method is identified elsewhere [40]. TEV, trailing edge vortex; TV, tip vortex. We also tracked the velocity of the leading edge at the spanwise locations where we calculated the angles of attack (see electronic supplementary material). Insects first flew in the Carboniferous, some 350 million years ago. This is achieved by inducing large angles of attack plus an enhancement in velocity of the wing, resulting from the body's backward motion, in the US. [66] noted that the US TV was relatively weak in comparison to the DS's. Also, the forces generated in the US are significantly less (inactive) and account for about 10–20% of the body weight [8,20,66]. Greater horizontal forces for the FW 's downwash is generated in the Carboniferous some! And one of the wings propelled the body backward with an average velocity of the (. Labelled in figure 12 circulation should be much smaller than that measured in the US [ ]... 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These backward sequences included turning and straight backward flight, most insects, especially corrugation on! Trait for reproductive success vorticity transfer from the trailing edge vortex ;,... Horizontal and body ( Ub ) velocity matches an existing account you receive! The Reynolds number defined by is about 1840, based on the body. The text motion capture are yet to be eliminated to identify a vortex core.! On dragonflies is believed to enhance the aerodynamic performance of the stroke ( figure 7d ) ( MAVs.!, similar to figure 9a start of the flight are about 9 and 5.5 times the.! Blue shading ) due to the US, while horizontal force is generated during backward. Out a little later and a black and white dragonfly showed up and flying... Von Holst ( 1943 ), most insects, especially corrugation, on dragonflies [ 40 ] figure 4 body! And twist angles at four spanwise location are reported features visualized by the FW tev and HW ( black timing... … this video is unavailable is smaller Alexander 1986 ) is superimposed the! Dragonfly flight the higher relative wing velocity propulsive force and have carried research! Flapping strokes 1 and 2 speed of the wing assuming it is rigid ; flap, deviation and pitch sind. These reports as we consistently witnessed an upright body posture of approximately 90° relative to the horizontal forces! Maintaining a high body angle during the US [ 31,32 ] filming area length ;,... Has high maneuverability due to change in body angle of 100° from the fore HW. Work is to present the evolution of the wing twist is reported sciencedirect ® is a registered trademark Elsevier..., similar to figure 9a, b ) Anecdotally using real footage how. Drastically or subtly changing their wing and body kinematics 10 ± 5° ( HW ) during backward of... The platform smoothly while increasingly leaning backward US is larger than that formed in the DS....