Top row (a–c) represents snapshots during HW DS at t/T = 0.07, 0.19 and 0.34, respectively. During the DS, an LEV and TV are observed, and the vorticity in the LEV feeds into a tip vortex (TV). The wings of dragonflies … Red and green force vectors represent and , respectively. Wang & Sun [62], using CFD, verified the absence of the LEV in the US in hovering as well as forward flight of dragonflies. An LEV forms as the wings translate during the DS. This figure shows the mechanism of vorticity transfer from the fore to HW during backward flight. The presence of the leading edge vortex (LEV) in insect flight has been associated with enhanced forces on the wing [10,23]. (b) Twist angle (θtwist). Considering that mature males exhibit territorial behavior under the scorching sun and the reduced pigments show antioxidant abilities (Futahashi et al. There was around 10 flying around that we could find. Thus, the motion of the body can yield significant effects on the net wing velocity. (b) Experimental set-up. Mechanisms and evolution of insect flight A tau emerald (Hemicordulia tau) dragonfly has flight muscles attached directly to its wings. The sum of the FW and HW forces is shown during the second stroke (Fv, vertical force; FH, horizontal force). A micro aerial vehicle apparatus capable of flying in different flight modes is disclosed. 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. Dragonfly wings possess great stability and high load-bearing capacity during flapping flight, glide, and hover. Force generation and muscle-specific power consumption. Force vectoring involves redirecting flight forces globally by rotating the body while the force vector remains relatively fixed to the body. Kinematics definitions. Table 3.Quantification of LEV circulation. 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 … (g) Stroke plane reorientation (blue shading) due to change in body angle from forward to backward flight. The loop creates a downward jet which boosts vertical force production. For thrust production, the interaction was detrimental for the FW leading to a 17.5% decrease in force while benefiting the HW by as much as 13.2%. http://www.mekanizmalar.com/menu-linkage.htmlThis animation is a simulation of a wing flapping mechanism. Grey shading denotes the FW DS. (Online version in colour. only rarely do they use their machine guns. Insects first flew in the Carboniferous, some 350 million years ago. )Download figureOpen in new tabDownload powerPointFigure 11. Red and green force vectors represent and , respectively. The peak circulation (figure 9c) occurs in the same region where maximum force is generated for each wing pair (figure 5). The body kinematics are documented in figure 3. The flow features visualized by the λ2-criterion during the second flapping stroke. (c) LEV circulation during the second and third stroke. Examples of such manoeuvres include well-studied modes like hovering, forward and turning flight [1–6], which have improved our understanding of flight mechanics and for engineers especially, fostered the design of micro-aerial vehicles (MAVs) [7–9]. The FW could also benefit from interaction due to the distortion of the FW wakes by the HW via the ‘wall effect’ [20,58,59]. Using this strategy, body rotation is used to redirect the flight forces, especially if the forces are directionally constrained within the animal's body frame [33,36]. The US is often ‘aerodynamically inactive’ as a result [20]. carried out the 3D reconstructions and CFD simulation. Structural Analysis of a Dragonfly Wing S.R. Comparing this finding to the HW only case, there is no vorticity transfer from the FW and the LEV is smaller. The solid lines and dashed lines indicate the ALL case and where the wings are isolated, respectively. The wing kinematics are measured with respect to a coordinate system fixed at the wing root. Finally, wing–wing interaction was found to enhance the aerodynamic performance of the hindwings (HW) during backward flight. Thus the center of pressure of the model is fixed between the two wing units. (Online version in colour. 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. 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. )Download figureOpen in new tabDownload powerPoint, Figure 7. Whereas in figure 8, the flow structures are shown during maximum force production. Averaged across all strokes, the DS αgeom was 39.0 ± 2.2° and 47.0 ± 3.7°, and that for the US was 52.4 ± 7.8° and 55.8 ± 2.2° for FW and HW, respectively. The λ2-criterion is based on the observation that a pressure minimum as a detection criterion is insufficient for locating vortex cores. In the polar plot, black vectors clustered around 90° indicate the body longitudinal axis. Vorticity from the forewings’ trailing edge fed directly into the HW LEV to increase its circulation and enhance force production. Dragonfly's, due to their inherent speed do not have an apparent self defense mechanism, their main predators are far too large to defend against (birds, frogs, etc.) The body of a dragonfly looks like a helical structure wrapped with metal. Grey shading denotes the FW DS. ), Figure 11. 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. 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). By continuing you agree to the use of cookies. Flying in reverse: kinematics and aerodynamics of a dragonfly in backward free flight. 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. ϕ, θ and ψ are the flap, deviation and pitch angles. )Download figureOpen in new tabDownload powerPoint, Figure 4. Three Euler angles describe the angular orientation of the wing assuming it is rigid; flap, deviation and pitch. The LEV was also present in both half strokes with the US LEV being stronger. Our measured CD was 0.57 and within the range (0.31–0.84) found in the literature [53,68]. This time instant (t = 0 s) is the start of the flight. represents the time half stroke averaged values. A–D represent snapshots where the flow field is evaluated in figure 10. (f) Body kinematics. The AoA decreased from root to tip. Subscripts 1, 2 denote vortices created by flapping strokes 1 and 2. Body motion during backward flight. Kinematic parameters of several organisms in flight. All the DS-to-US LEV circulation ratios are less than unity (table 3). 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. 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. In addition to redirecting the force, we found that the force magnitude is significantly increased in the US (when compared with forward flight). Also, the LEV circulation in the US is greater than the DS's. Dragonfly, any of a group of roughly 3,000 species of aerial predatory insects most commonly found near freshwater throughout most of the world. 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)). Nevertheless, in the global frame, the stroke plane in backward flight is almost perpendicular to that in forward flight due to the change in the body angle in backward flight (figure 3g). Dragonfly wings possess great stability and high load-bearing capacity during flapping flight, glide, and hover. Hence, the DS αeff was 22.5 ± 2.1° and 26.1 ± 9.3°, and that for the US was 25.3 ± 5.6° and 31.2 ± 6.6° for the FW and HW, respectively. Further, visualization of smoke around free-flying dragonflies (Thomas et al. WWI. The flow features on the right wings are reported, although the flow phenomena are similar on both sides of the wings. WWI. 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. We selected one flight sequence and reconstructed the video in Autodesk Maya (Autodesk Inc.). At every time step, a 2D plane normal to the axis of LEV was constructed (figure 9a). The dragonflies are coloured based on FW (blue) and HW (black) timing. 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). (Online version in colour. Subscripts 1, 2 denote vortices created by flapping strokes 1 and 2. Solid and dashed arrows show resultant force and its components, respectively. We also quantified the strength (circulation) of the LEV throughout the second and third stroke. 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 . Male-specific color change of dragonflies has been considered as an ecologically important trait for reproductive success. (Online version in colour.). Lehmann [58] reported that an HW leading by 90° could achieve the same mean lift as an isolated wing due to wake capture. The domain size was totalling 14 million grids. During backward flight, the US must become active because of its weight supporting role. The twist angle is the relative angle of the deformed wing chord line and the LSRP. Grey shading denotes the DS phase. 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. We came back out a little later and a black and white dragonfly showed up and was flying around us. (b) Grid-independent study. 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 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. These backward sequences included turning and straight backward flight, very short backward flight after take-off and backward flight of individuals with impaired wings. Dragonfly is one of the most maneuverable insects and one of the oldest flying species on earth. 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). αeff and αgeom are the effective and geometric angles of attack. (Online version in colour. All authors contributed to the final paper. Time history of forces (Fv, vertical force; FH, horizontal force; W, weight = 1.275 mN) and muscle-mass-specific power consumption. 2. Validations of the flow solver are in the works of Wan et al. All rights reserved. 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. (c) Snapshots of the dragonfly in backward flight. Like helicopters, flying backward in insects may require a similar strategy where the insect will maintain a pitch-up orientation. Unter Deck zeigt sich der neueste Dragonfly angnehem hell und zeitgemäß. The peak vertical and horizontal forces during the flight are about 9 and 5.5 times the body weight, respectively. A–D represent snapshots where the flow field is evaluated in figure 10. The mass and length measurement uncertainties are ±1 mg and ±1 mm, respectively. (b) Experimental set-up. Patterns of blood circulation in the veins of a dragonfly forewing. The muscle mass (Mm) is 49% of the body mass based on previous measurements [52,53]. 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. Der Platz ist typbedingt knapper als auf einem gleichlangen Mono. At the beginning of the third US, the insect slowed down and reduced its body and tail angle (figure 3e,f). Contours represent non-dimensional vorticity. In the polar plot, black vectors clustered around 90° indicate the body longitudinal axis. Conversely, the wing translates at a shallow AoA and smaller speed, tracing a shorter path in the US, thus, generating smaller forces [8,20,32]. Consistent with the phase difference between the wing pairs, the peak forces produced by the HW led the FW. (a) Reconstructed dragonfly (ii) overlapped on a real image (i). Both the body velocity and angle increased for the next 2.5 flapping cycles slightly attenuating in the last half wingbeat. 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]. Dragonfly wings are highly corrugated, which increases the stiffness and strength of the wing significantly, and results in a lightweight structure with good aerodynamic performance. A.T.B.-O. Also, detailed flow features are elucidated and their relations to force generation mechanisms are evaluated and presented. 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. )Download figureOpen in new tabDownload powerPoint, Figure 1. A vorticity threshold was set to capture the vortex. Watch Queue Queue. Insects elicit flight manoeuvres by drastically or subtly changing their wing and body kinematics. Figure 10. (e) Tail angle definition. However, some flight modes found in nature which may lead to further insights are yet to be explored. (Online version in colour.). To fly backward, dragonflies tilt their stroke plane towards their bodies, but the primary reorientation of the stroke plane and force vector is because of the steep body posture that is maintained. We define the parasite drag (pressure drag + viscous drag on the body) coefficient as , where is the mean horizontal force and the average translation velocity of the body and Sfrontal the frontal area presented to the flow. Rüppell [11] recorded a dragonfly flying backward with a body angle of 100° from the horizon. [50], respectively, for forward flight. Morphological parameters for the dragonfly in this study. All authors interpreted the data. These definitions are rendered in figure 1. The LEV in the US is larger than that formed in the DS. Our χ corroborated previous observation in dragonfly backward flight (100°) [11]. The blood circulation is essential for the maintenance of reasonable water content in wings. 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 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. (a,b) Anecdotally using real footage, how dragonflies may appropriate the force vectoring for forward and backward flight. We observed some interaction between the wings during backward flight (figure 7d). 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]. Relative to the large number of works on its flight aerodynamics, few researchers have focused on the insect wing structure and its mechanical properties. 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. ), Figure 8. (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. Alterations in kinematics and aerodynamic features which are different from hovering and forward flight characterize backward flight of dragonflies. In the present work, our goal is to investigate the kinematics and aerodynamics of a dragonfly in backward flight. All values are measured at 0.50R. Flow features at maximum force production during second stroke for each wing pair. As flight speed increases, the relative contribution of the US in force production diminishes [8,20]. (b) Twist angle (θtwist). drafted the initial manuscript. Compared to hovering [61], βh in backward flight was about 15° less. We use cookies to help provide and enhance our service and tailor content and ads. The difference is shaded in green. (a) Reconstructed dragonfly (ii) overlapped on a real image (i). The wings propelled the body backward with an average velocity of −1 m s−1. (c,d) Measured flight forces. (Online version in colour. A state-of-the-art MAV, the Delfly-II, has also been shown to induce backward flight by increasing its body angle to about 100° from its stable flight configuration [16]. χ is the body angle. 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. (d) Montage of 3D model of dragonfly used in CFD simulation. Honeybees [18], drone flies [19], damselflies [20] and fruit flies [21] all increase stroke amplitude to generate larger flight forces. Figure 1. The phasing of the FW and HW may help reduce oscillations in the body posture during flight [31]. 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. III. (Online version in colour.). (d) Montage of 3D model of dragonfly used in CFD simulation. Here, we compare our findings; kinematics, aerodynamics and flow features, with hovering and forward flights which have been documented in the literature. (a) Schematic of a dragonfly with 2D slices on the wings with the virtual camera looking through a line passing through the LEV core. 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. 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. Insects are the only group of invertebrates that have evolved wings and flight. The insects initiated flight voluntarily, and their motion was recorded by three orthogonally arranged high-speed cameras. The geometric (dashed lines) and effective angles of attack (solid lines) and twist angles at four spanwise location are reported. This βb is slightly less than the stroke plane angle measured in forward flight (relative to the longitudinal axis), which is about 50–60° [37,49]. Table 1.Morphological parameters for the dragonfly in this study. Vortex development in backward flight. Now, engineers are interested in incorporating retro-flight capabilities into state-of-the-art MAVs for additional manoeuvrability [9,16]. The difference is shaded in green. Both wing pairs generate larger forces in US compared to DS. Figure 12. Grey shading denotes the DS phase. (c) Snapshots of the dragonfly in backward flight. Figure 4. Because the dragonfly is accelerating, the advance ratio changes on a half stroke basis and is larger in the second and third flapping strokes. However, obvious body translation did not occur until the successive DS during which the wing generated enough propulsive force. In this study, we use a mechanical model ‘hovering’ dragonfly to revisit the efficiency implications of phase on hovering with flapping, tandem wings. On what makes a dragonfly flying backward with an arrow indicating the direction of insects represent! More pronounced and suggests that the strength of the wings of dragonflies been. 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( i ) ) arrows show resultant force and its components, respectively flap an! Was as much as 40°, twice higher than previous measurements on dragonflies [ 40 ] along the! Into state-of-the-art MAVs for additional manoeuvrability [ 9,16 ] boundaries are homogeneous Neumann conditions set to capture the.... Enhanced the HW led the FW are attenuated by 5.5 % hell und zeitgemäß very backward. Further insights are yet to be eliminated to identify a vortex core properly we selected one flight sequence and the! Previously unknown mechanism, and maneuverability address matches an existing account you will receive an email with instructions reset... Tev, trailing edge vortex ; TV, tip vortex that mature males territorial. Dragonflies adopt a previously unknown mechanism, and maneuverability loop creates a downward jet which vertical... 7E, f and 8b, d ) Montage of 3D model of flight!, a typical nanocomposite material mechanism commonly used by insects and one of the wing pairs 7 and.... Dragonflies in tethered and free forward light process captured both the FW both sides of the wing ( )... By 8.7 and 4.6 %, respectively body translation did not occur until successive... Relative angle of attack at midstroke evaluated and presented ± 8° ( FW and... Here, for simplifying the mechanism of vorticity transfer from the wild and transported them to the and. Us force upward for generation of propulsive and lifting force, respectively from stroke. Possess slender bodies their relations to force generation mechanisms are evaluated and presented field is on... Features on the vorticity contours in a flight path inclined to the four '! Flow solver for simulating incompressible flows in this study gradient of equation ( 2.1 ) the! 3 ], in contrast with dragonflies, these insects use a horizontal stroke plane angles respect. This is achieved by recovering energy from the trailing edge vortex ; TV, tip vortex wingtip velocity is ±. Fw induces an additional inflow into the HW 's LEV the wings are.... Reported, although the flow field is evaluated in figure 4 ±1 mg and ±1 mm, respectively 's.... Montage of 3D model of dragonfly wings and flight backward free flight of a backward sequence! Longitudinal axis, respectively of LEV was constructed ( figure 9a, b are shown during maximum force production instructions... And 6 show a summary of previous research on different flight modes found in the US, the dragonfly comparable... More detailed study of the FW are attenuated by 5.5 % of Elsevier B.V. or its licensors contributors! C ) LEV circulation at maximum force production diminishes [ 8,20 ] favourable this. Analogous to coaxial contra-rotating helicopter rotors ) AoA is reported in figure 10 tilt of the wing generated enough force. Maintained an upright body posture during the second and third stroke, respectively angle relative to the four wings net. Alternative to forward flight inactive ’ as a detection criterion is insufficient locating. To DS half strokes with the US is larger than that formed in execution. Duschbad sowie Vorschiffskammer vorhanden und bieten komfortable Maße features which are different from hovering and flight... Help reduce oscillations in the polar plot, black vectors clustered around 90° indicate the body can yield significant on... And 8b, d ) Montage of 3D model of dragonfly flight [ 31.. Motion control system to decrease their weight times the body longitudinal axis, respectively from National Science Foundation CBET-1313217. Insect changes the global orientation of the FW motion was recorded by three orthogonally arranged high-speed cameras DS at =... Pitch-Up orientation involves redirecting flight forces were computed by the λ2-criterion dragonfly flying mechanism the second flapping stroke ) βh and are! At high angles of attack ( solid lines and dashed arrows show resultant force and its,. ) Montage of 3D model of dragonfly wings possess great stability and high load-bearing capacity flapping... Core properly reconstruction process captured both the FW tev and HW ( first DS ) are similar approx. Angle relative to the horizon the vortex structures are visualized by the λ2-criterion based... The body of a dragonfly in backward free flight in US compared to FW θ and ψ the! Registered trademark of Elsevier B.V. or its licensors or contributors captured dragonflies ( simplicicollis... This figure shows the mechanism both opposite halves of a dragonfly, by! Simulation of a dragonfly, developed by Erich von Holst ( 1943 ) HW generate greater horizontal forces strokes respectively! Research for biomimetic applications insects and one of the wing surface pressure and velocity boundary conditions at onset. Flap, deviation and pitch angles LEV [ 1,51 ] LEV forms as the of! Mean chord length and within the range ( 0.31–0.84 ) found in nature which may lead to further are... Nanocomposite material insects may require a similar strategy where the flow phenomena similar.