Thomas et al. Taking into account the body motion, we found that αgeom was significantly reduced. (a) βh and βb are the stroke plane angles with respect to the horizontal and body longitudinal axis, respectively. 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. Because force production is proportional to wing velocity squared, insects adjust wing speed by altering the stroke amplitude and/or frequency [5,11,17]. 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. 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 wing kinematics are measured with respect to a coordinate system fixed at the wing root. Slices similar to figure 9a,b are shown here to elucidate WWI. Rüppell [11] recorded a dragonfly flying backward with a body angle of 100° from the horizon. In contrast with backward flight, during forward and hovering flight, most of the flight force is produced in the DS [20,31,72]. The flow features on the right wings are reported, although the flow phenomena are similar on both sides of the wings. (Online version in colour.). (b) Spanwise vorticity on FW during the (i) DS (dorsal surface shaded in grey) and (ii) US in the third stroke (ventral surface shaded in blue). During this time he worked on developing a flying robot that employed the principles of the dragonfly's mechanisms of flight. The flow features visualized by the λ2-criterion during the second flapping 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 . https://doi.org/10.1016/j.crme.2011.11.003. For display, the meshes coarsened four times. The λ2-criterion is based on the observation that a pressure minimum as a detection criterion is insufficient for locating vortex cores. 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.) All authors interpreted the data. (Online version in colour. Hence, the LEV circulation should be much smaller than that measured in the DS. In these flight modes, the DS is conventionally regarded as vertical force producing and the US, thrust (horizontal force) producing [11,31,50]. The body kinematics are documented in figure 3. As the wings separate from each other during the excursion, the initial increase in HW LEV circulation is maintained in addition to the new vorticity influx formed as the LEV grows during translation (figure 10b–d). The structure and mechanical properties of dragonfly wings and their role on flyability. Mechanism of WWI. Grey shading denotes the DS phase. Daher lassen sich die Schwimmer über einen ausgefeilten Mechanismus seitlich beiklappen. Finally, wing–wing interaction was found to enhance the aerodynamic performance of the hindwings (HW) during backward flight. Mechanism of WWI. Also, both the FW and HW have LEVs on them. 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. Top row (a–c) represents snapshots during HW DS at t/T = 0.07, 0.19 and 0.34, respectively. At these intermediate angles of attack, insect wings usually carry a stable LEV [1,51]. ϕ, θ and ψ are the flap, deviation and pitch angles. Likewise, Mukundarajan et al. (d) Montage of 3D model of dragonfly used in CFD simulation. The research objectives are then presented along with the research contributions. A micro aerial vehicle apparatus capable of flying in different flight modes is disclosed. Time history of forces (Fv, vertical force; FH, horizontal force; W, weight = 1.275 mN) and muscle-mass-specific power consumption. 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. There might be difficulty in four wings motion control system to decrease their weight. ϕ, θ and ψ are the flap, deviation and pitch angles. The FW TEV and HW LEV are linked together due to interaction (figure 11a). Greater forces are produced by HW compared to FW. 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]. Comparing the CD measured from our simulation (Reynolds number based on body length, Reb ∼ 3860) with results for forward flight of dragonflies of similar Reb approximately 2460–7790 in the literature, the results were comparable indicating that an upright body posture did not substantially influence body drag production. The US circulation, shown in dashed lines, is higher than the DS circulation, consistent with greater flight force generated in the US. (a,b) Anecdotally using real footage, how dragonflies may appropriate the force vectoring for forward and backward flight. 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. Validations of the flow solver are in the works of Wan et al. Like helicopters, flying backward in insects may require a similar strategy where the insect will maintain a pitch-up orientation. 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. Subscripts 1, 2 denote vortices created by flapping strokes 1 and 2. The wing structure, especially corrugation, on dragonflies is believed to enhance aerodynamic performance. The tail angle is the angle between the thorax and the tail. dragonflies, damselflies, etc. Figure 3. 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). (Online version in colour. ), it is known that a wing with an LEV imparts greater momentum to the fluid, leading to the production of larger forces than under steady-state conditions [26–29]. An accurate three-dimensional (3D) surface reconstruction technique coupled with a high-fidelity computational fluid dynamics (CFD) flow solver [39] is used to quantify the coordination of the wing and body motion and to identify how flight forces are generated during flight. Body motion during backward flight. The wings propelled the body backward with an average velocity of −1 m s−1. 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). )Download figureOpen in new tabDownload powerPoint, Figure 6. 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). The bottom row (d–f) represents snapshots during HW US at t/T = 0.52, 0.70 and 0.87, respectively. Wang & Sun [62], using CFD, verified the absence of the LEV in the US in hovering as well as forward flight of dragonflies. The mass and length measurement uncertainties are ±1 mg and ±1 mm, respectively. L, body length; R, wing length from root to tip, , mean chord length. This is achieved by recovering energy from the wake wasted as swirl in a manner analogous to coaxial contra-rotating helicopter rotors. Effect of WWI during flight (all strokes combined). The insect left the platform smoothly while increasingly leaning backward. The dragonflies are coloured based on FW (blue) and HW (black) timing. During backward flight, the US must become active because of its weight supporting role. 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. (Online version in colour. The mean stroke plane angle relative to the horizon (βh) is 46.8 ± 5.5° for the FW and hindwings (HW). 26, 28, 29, 55, 56, 57 Researches on flies, 29, 58 bees, 29, 58, 59, 60 hoverflies, 61, 62, 63 wasps, 29 locusts, 29, … 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. All rights reserved. Thus the center of pressure of the model is fixed between the two wing units. We dotted the dragonflies' wings for tracking purposes and placed the insects in a filming area. (Online version in colour.). Male-specific color change of dragonflies has been considered as an ecologically important trait for reproductive success. The region of interaction is shown in dashed lines with an arrow indicating the direction of vorticity transfer (a (i)). The advance ratio (J), defined as the ratio of the average body to wingtip velocity is −0.31 ± 0.12. χ is the body angle. Simulations of dragonfly-like wings at different advance ratios and phase differences indicated that total forces of the FW and HW are influenced by wing–wing interaction (WWI) when the HW lead the FW [56]. (a) Reconstructed dragonfly (ii) overlapped on a real image (i). The AoA decreased from root to tip. In this study, we investigated the backward free flight of a dragonfly, accelerating in a flight path inclined to the horizontal. Their flight performance far exceeds other insects. The wings of dragonflies … 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. (Online version in colour. Unlike most other insects, such as flies, wasps, and cicadas, that have either reduced hindwings or functionally combined forewings and hindwings as a single pair, dragonflies have maintained two pairs of wings throughout their evolution [1]. II. Figure 9. The circulation increases along the span and tapers towards the tip. The presence of the FW induces an additional inflow into the LEV which is favourable in this case. In the text, the mid-span (0.5R) AoA is reported. Jeong & Hussain [47] opined that unsteady straining could cause a pressure minimum without vortical motion and viscous effects could also eliminate the pressure minimum in the flow when there is vortical motion. [30] measured the LEV contribution to weight support during the forward flight of dragonflies and concluded that dragonflies could sustain their weight from the contribution of the LEV on the forewings (FW) alone. 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. From their smoke visualization and analysis, there was no hint of an LEV to enhance lift in the US. In figure 10, the vortical structures are projected on a 2D slice cut at mid-span, similar to figure 9a. (c) Snapshots of the dragonfly in backward flight. The solid lines and dashed lines indicate the ALL case and where the wings are isolated, respectively. Insects first flew in the Carboniferous, some 350 million years ago. 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. This time instant (t = 0 s) is the start of the flight. More precisely, we aim to identify the role that force vectoring plays in the execution of a backward flight manoeuvre. The difference is shaded in green. Jongerius & D. Lentink Received: 30 August 2009 /Accepted: 8 September 2010 /Published online: 26 October 2010 # The Author(s) 2010. Body motion during backward flight. Vortex development in backward flight. The twist angle is the relative angle of the deformed wing chord line and the LSRP. Also, the forces generated in the US are significantly less (inactive) and account for about 10–20% of the body weight [8,20,66]. Funding support from National Science Foundation (CBET-1313217) and Air Force Office of Scientific Research (FA9550-12-1-007). Grey shading denotes the FW DS. (Online version in colour.). Electronic supplementary material is available online at https://dx.doi.org/10.6084/m9.figshare.c.4131254. 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]. Red and green force vectors represent and , respectively. Both the body velocity and angle increased for the next 2.5 flapping cycles slightly attenuating in the last half wingbeat. Table 2.Forces from three different grids set-up. Abstract. Force generation and muscle-specific power consumption. They intercept prey This figure shows the mechanism of vorticity transfer from the fore to HW during backward flight. Velocities, accelerations and kinematics of flapping flight, Surface tension dominates insect flight on fluid interfaces, Computational investigation of cicada aerodynamics in forward flight, 3D reconstruction and analysis of wing deformation in free-flying dragonflies, Scaling law and enhancement of lift generation of an insect-size hovering flexible wing, State-space representation of the unsteady aerodynamics of flapping flight, Vortex dynamics and new lift enhancement mechanism of wing–body interaction in insect forward flight, A versatile sharp interface immersed boundary method for incompressible flows with complex boundaries, Wing kinematics measurement and aerodynamics of a dragonfly in turning flight, Three-dimensional flow structures and evolution of the leading-edge vortices on a flapping wing, Study of lift enhancing mechanisms via comparison of two distinct flapping patterns in the dragonfly, Dragonfly flight. The average Euler angles are shown. The region of interaction is shown in dashed lines with an arrow indicating the direction of vorticity transfer (a (i)). Contours represent non-dimensional vorticity. Considering that mature males exhibit territorial behavior under the scorching sun and the reduced pigments show antioxidant abilities (Futahashi et al. We used an in-house immersed boundary method flow solver for simulating incompressible flows in this study. therefore they rely on speed, intelligence, and maneuverability. 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]. Although just qualitatively characterized in the literature, it has been documented that insects use backward flight for predator evasion, prey capture, flight initiation, station keeping and load lifting [10–15]. Enter your email address below and we will send you your username, If the address matches an existing account you will receive an email with instructions to retrieve your username. I. Gliding flight and steady-state aerodynamic forces, Three-dimensional flow and lift characteristics of a hovering ruby-throated hummingbird, Lift production in the hovering hummingbird, https://dx.doi.org/10.6084/m9.figshare.c.4131254, doi:10.1146/annurev.fluid.36.050802.121940, The reverse flight of a monarch butterfly (Danaus plexippus) is characterized by a weight-supporting upstroke and postural changes. Willmott et al. (Online version in colour. 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. Dragonfly wings possess great stability and high load-bearing capacity during flapping flight, glide, and hover. The LEV in the US is larger than that formed in the DS. This table reports the contribution of each half stroke to the total aerodynamic force during a flapping cycle in different flight modes of insects. A classic example is backward flight. WWI. (a) Schematic of a dragonfly with 2D slices on the wings with the virtual camera looking through a line passing through the LEV core. αeff and αgeom are the effective and geometric angles of attack. Conversely, to transition to backward flight, a helicopter rotates the force vector by inducing a nose-up motion on the fuselage and tilts the tip-path plane backward. Wing kinematics and twist. was oriented at 107 ± 15° (FW) and 96 + 18° (HW). Scientists have been intrigued by them and have carried out research for biomimetic applications. Experimental details. Kinematics definitions. This figure shows the mechanism of vorticity transfer from the fore to HW during backward flight. represents the time half stroke averaged values. We solved the incompressible Navier–Stokes equation (equation (2.1)) using a finite difference method with second-order accuracy in space and a second-order fractional step method for time stepping. 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]. Copyright © 2011 Académie des sciences. http://www.mekanizmalar.com/menu-linkage.htmlThis animation is a simulation of a wing flapping mechanism. Here, we compare our findings; kinematics, aerodynamics and flow features, with hovering and forward flights which have been documented in the literature. 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. (c,d) Measured flight forces. Because the dragonfly is accelerating, the advance ratio changes on a half stroke basis and is larger in the second and third flapping strokes. 4 mN), while the peak vertical force of the HW is about twice FW in the second and third strokes as the insect ascends (see §3.1.1). The average body angle during the entire flight duration was approximately 90°. 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). 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. Whereas in figure 8, the flow structures are shown during maximum force production. Grey shading denotes the DS phase. Medium grids are shown in (a). (d,e) Spanwise distribution of LEV circulation at maximum force production during the second and third stroke, respectively. These backward sequences included turning and straight backward flight, very short backward flight after take-off and backward flight of individuals with impaired wings. Mechanisms and evolution of insect flight A tau emerald (Hemicordulia tau) dragonfly has flight muscles attached directly to its wings. 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 loop creates a downward jet which boosts vertical force production. Thus, the motion of the body can yield significant effects on the net wing velocity. The geometric (dashed lines) and effective angles of attack (solid lines) and twist angles at four spanwise location are reported. The forces and muscle-mass-specific power consumption are displayed in figure 5. The flow features visualized by the λ2-criterion during the second flapping stroke. 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. In addition to body motion, we observed some tail movement typical of dragonfly flight. Computational set-up. 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. Furthermore, we will identify other aerodynamic mechanisms related to backward flight, if any, and quantify their contributions with regard to this unique flight mode. (Online version in colour. Vorticity from the forewings’ trailing edge fed directly into the HW LEV to increase its circulation and enhance force production. The reconstruction process captured both the kinematics and deformations. (c,d) Measured flight forces. The peak vertical and horizontal forces during the flight are about 9 and 5.5 times the body weight, respectively. (a) βh and βb are the stroke plane angles with respect to the horizontal and body longitudinal axis, respectively. (Online version in colour. flying insects. At the beginning of the third US, the insect slowed down and reduced its body and tail angle (figure 3e,f). A more detailed study of the 3D reconstruction method is identified elsewhere [40]. Visualization of vortical structures at mid-span during WWI. 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. Der Platz ist typbedingt knapper als auf einem gleichlangen Mono. ), Figure 8. Force vectors in mid-sagittal plane. During backward flight, the dragonfly maintained an upright body posture of approximately 90° relative to the horizon. 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. The twist was as much as 40°, twice higher than previous measurements on dragonflies [40]. )Download figureOpen in new tabDownload powerPointFigure 11. Both wing pairs generate larger forces in US compared to DS. There was a preparatory stage (t = −20 ms to 0 s). Contours represent non-dimensional vorticity. The problems in dragonfly mechanism are identified and explained. In this study, we use a mechanical model ‘hovering’ dragonfly to revisit the efficiency implications of phase on hovering with flapping, tandem wings. carried out the 3D reconstructions and CFD simulation. (b) Twist angle (θtwist). III. 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. and background of this research. The tail motion trailed the body's by about half a wingbeat, although the profile of the time histories was similar. Most of the vertical force is generated during the US, while horizontal force is generated in the DS. Flow features at maximum force production during second stroke for each wing pair. Flow features at maximum force production during second stroke for each wing pair. Also, detailed flow features are elucidated and their relations to force generation mechanisms are evaluated and presented. For force production, a strong LEV was present on both wing pairs. Patterns of blood circulation in the veins of a dragonfly forewing. Contrary to previous works on dragonfly forward flight [1,30,62], the presence of the LEV was not limited to the FW but was evident on the HW as well [51]. We use cookies to help provide and enhance our service and tailor content and ads. (Online version in colour. Time history of forces (Fv, vertical force; FH, horizontal force; W, weight = 1.275 mN) and muscle-mass-specific power consumption. Dragonfly species are characterized by long bodies with two narrow pairs of intricately veined, membranous wings that, … 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. Hence, unsteady straining and viscous effect need to be eliminated to identify a vortex core properly. )Download figureOpen in new tabDownload powerPoint, Figure 5. 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