Dragonfly Wings

The Dragonfly Wings is a clothing item worn on the back. It was originally released in June 2015 at Jam Mart Clothing for 1,300 Gems. Not to be confused with the Pet Dragonfly Wings (Pet). The Dragonfly Wings is a clothing item worn on the back. It was originally released in June 2015 at Jam Mart Clothing for 1,300 Gems.

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. How insect wings carry aerodynamic and inertial loads, and how the resonant frequency of the flapping wings is tuned for carrying these loads, is however not fully understood. To study this we made a three-dimensional scan of a dragonfly ( Sympetrum vulgatum) fore- and hindwing with a micro-CT scanner. The scans contain the complete venation pattern including thickness variations throughout both wings. We subsequently approximated the forewing architecture with an efficient three-dimensional beam and shell model.

We then determined the wing’s natural vibration modes and the wing deformation resulting from analytical estimates of 8 load cases containing aerodynamic and inertial loads (using the finite element solver Abaqus). Based on our computations we find that the inertial loads are 1.5 to 3 times higher than aerodynamic pressure loads. We further find that wing deformation is smaller during the downstroke than during the upstroke, due to structural asymmetry. The natural vibration mode analysis revealed that the structural natural frequency of a dragonfly wing in vacuum is 154 Hz, which is approximately 4.8 times higher than the natural flapping frequency of dragonflies in hovering flight (32.3 Hz). This insight in the structural properties of dragonfly wings could inspire the design of more effective wings for insect-sized flapping micro air vehicles: The passive shape of aeroelastically tailored wings inspired by dragonflies can in principle be designed more precisely compared to sail like wings —which can make the dragonfly-like wings more aerodynamically effective. Recently designed flapping micro air vehicles have been developed inspired by insect flight –.

These flapping MAVs generate both lift and thrust by flapping their sail-like wing structures that deform primarily due to aerodynamic loading , Fig. Whereas flapping MAVs typically employ slack wings, the wings of most insects are very stiff compared to the sail-like wing structures of MAV wings ( e.g. How insect wings function structurally under dynamic wing loading is not yet fully understood, although existing studies have generated novel insight in how the venation pattern of insects is critical for their load baring capacity and aeroelastic function. Counter-intuitively the corrugated wings of insects provide good aerodynamic performance at low Reynolds numbers –, while providing good structural strength and stiffness. Numerical analyses of insect wings have been performed by Smith , Kesel et al.

, Herbert et al. , Combes and Daniel – and Wootton et al. to better understand the structural function of insect wings under different loading regimes. Smith performed a modal analysis of a quasi-two-dimensional finite element model (FEM) of the fore- and hindwing of a moth, to correlate the distribution of mass and stiffness. increased model fidelity to study structural stabilization of dragonfly wings by vein corrugation. Herbert et al. numerically explored the mechanisms that lead to the umbrella effect, a mechanism of camber generation in the hindwing fans of orthopteroid and dictyopteroid insects, as described by Wootton.

They built cambered FEMs of the hindwing of a grasshopper ( Schistocerca gregaria). Combes and Daniel created a quasi- two-dimensional FEM to explore how damping affects a Manduca sexta forewing. Wootton et al. performed a modal and impact analysis on a slightly cambered simplified model of a Manduca sexta wing.

Their results indicate that the natural vibration frequency of a Manduca wing is equal to the flapping frequency of Manduca in flight. They also addressed several challenges previous studies encountered in accurately describing wing morphology.Here we focus on the three-dimensional structural function of dragonfly wings (Fig. ), because their venation pattern has remained surprisingly similar during their evolution, suggesting this conserved feature plays an important role in flight. The Protodonata, the ancestors of the dragonflies (Odonata), were among the earliest fliers in the Carboniferous.

Approximately 350 million year old fossils of Meganeuridae tell us that they flew with wingspans of up to 75 cm. Their wings are similar enough to modern shapes to suggest comparable flight capabilities, although perhaps with less refinement ,. Modern dragonfly wings have similar wing architecture, but are much smaller in size. The relatively constant wing architecture across dragonfly evolution suggests that the wing architecture of dragonflies functions well over a large range of wingspans. Furthermore, dragonflies are among the more agile flyers.

They hunt in flight, are highly manoeuvrable and even mate mid-air. Dragonflies often cope with accelerations of up to 4 g in a straight line and 9 g in steep turns as documented in high speed video recordings. This shows that dragonfly wings most likely have evolved into effective wings that function well under diverse high-performance flight conditions. Understanding how these wings function structurally could, therefore, inspire the design of more effective wings for insect-sized micro air vehicles.In our structural analysis of dragonfly wings we digitized a dragonfly fore- and hindwing. The geometry of the forewing was captured accurately enough to be modeled well with an array of linked beams and shells to obtain an efficient Finite Element Model.

We use this FEM to reveal deformations, and natural vibration characteristics of a dragonfly forewing, to obtain better insight in the functional morphology of dragonfly wings. ( a) Digital reconstruction of the hindwing of Sympetrum vulgatum. Dark areas are thick, light areas are thin (linear scale from dark to light). ( b–e) Cross-sectional micro-CT image near the wing root showing the highly corrugated wing architecture build up by the wings veins and membrane. Cross sections more distant of the root ( c–e) show less corrugation and the cross section near the wing tip ( e) reveils the hollow pterostigma. The main difference between this figure and 3 are the much thinner veins and membrane.

Dragonfly Forewing LoadingDuring flapping, the wing experiences both inertial and aerodynamic loads that need to be carried by the wing structure. Previous studies suggested that the inertial loads are higher than the aerodynamic loads, from 2 up to 10 times.

If such a load ratio also holds for dragonfly wings is unknown. To calculate the wing loads we made an analytical model of both the aerodynamic load needed to support the weight of the animal, and the inertial loads that result from the flapping motion of the wing that can support the weight. Super fancy pants adventure pc. Aerodynamic load modelWe focused on the lift forces the wing needs to bear to oppose body weight, in this force calculation we neglected the loading of the wing due to drag force. Lift in flapping flight is generated by three distinct mechanisms: delayed stall, rotational circulation and wake capture. Delayed stall generates a leading edge vortex (LEV) during the swing phases of the stroke –.

Rotational circulation and wake capture occur primarily during stroke reversal, while the LEV is prominent mid stroke. Because the total lift generated during the swing phase of the wing is typically considerably higher than the lift generated during stroke reversal , we focused on lift generated by delayed stall; the LEV. Another aerodynamic load component is known as ‘added mass’ or ‘virtual mass’. The added mass varies from 0.3 up to 1.2 times the wing mass ,. Added mass is difficult to model accurately and smaller than lift force, therefore we neglect it in our basic force model. Finally we ignore drag force altogether, because an accurate estimate of both its magnitude and distribution over the wing is still unavailable for dragonflies.We assumed that average lift generated by a forewing during a flapcycle is equal to ¼ of the weight W of the insect (because of its four wings) and equal during down- and upstroke.

Micro computed tomography scanning proved to be a successful method to digitise a dragonfly forewing in three dimensions. Subsequently created thickness distributions showed decreasing thickness of veins and membranes from root to tip and from leading to trailing edge. We analysed results from the numerical analysis using custom Matlab algorithms. Maximum inertial loads appeared higher than maximum aerodynamic loads in spanwise direction. Structural deformations were small, the maximum deflections were found during stroke reversal (1.5 mm) and were located at the wing tip. The numerical analyses also revealed that wing bending during upstroke was higher when compared to downstroke. The latter is likely caused by the asymmetrical shape of the wing due to camber and positions of the valleys and hills in the wing build up by radial veins.

Our vibration analysis shows that the wing’s first natural frequency in vacuum is approximately 4.8 times higher than the flapping frequency of Sympetrum vulgatum. Digitisation and Image Analysis of a Dragonfly WingOur results show that three-dimensional digitisation of thick insect wings, such as those from dragonflies, is possible when using modern micro-CT scanners.

On the opposite side of the spectrum is a bright pixel or, as many manufacturer’s call it a “bright dot”. Dead pixels check.

Micro-CT proved to be a relatively easy, fast and efficient way to capture the morphology of a dragonfly wing (Figs., ). The only downside of micro CT-scanning is that our wings were slightly deformed near the trailing edge, because the wings needed to be dried to reduce scatter due to evaporation in the warm scanner.

The deformations due to drying most likely affected wing stiffness to some degree. The trailing edge veins and membrane are, however, significantly thinner than the rest of the wing, which decreases the effect of local deformation on wing stiffness, because it balances their relative large distance with respect to the centroid of the wing. We determined the thickness distribution of the wing (Fig. ) based on the cross-sectional image stack of the wing.

As expected, thick veins are located near the wing root and the leading edge. Some of the continuous veins that span from leading to trailing edge are thicker as well.

The thicknesses of thick veins range from 75 to 150 μm. The veins that form the hexagonal pattern are thinner, with thickness ranging from 10 to 50 μm. The thickness distribution of membranes is similar; thick membranes near the leading edge and root, ranging between 15 and 25 μm. Thin membranes range in thickness from 3.6 μm up to 15 μm. The hollow pterostigma of the wing has a maximum thickness, measured from the bottom to top side of the pterostigma, of approximately 220 μm. Load DistributionsWe compared the maximum aerodynamic load at midstroke with the maximum inertial load at stroke reversal.

The loads are summed along the chord to obtain a spanwise distribution along the wing (Fig. ). The distributions are similarly shaped from root to tip, with local maxima for inertial load at the nodus (±45% wing length r) and pterostigma (±85% r). The maximum aerodynamic load is found at about 65% of the wingspan ( r). We found that the inertial forces along the wingspan are approximately 1.5–3 times higher than the aerodynamic forces.

This matches the estimation of Ennos that spanwise bending moments due to the inertia of flapping wings are about twice as large as those due to aerodynamic forces. The simultaneously plotted mass distribution shows that local spanwise mass maxima appear at the wing nodus and the pterostigma. The peaks suggest that these areas have a relatively large influence on inertial deformation responses.