Structural Analysis of a Dragonfly Wing

Abstract

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 insectsized 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.

Feather roughness reduces flow separation during low Reynolds number glides of swifts

“…The surface roughness thus effectively controls the dynamics of laminar separation bubble formation throughout the glide envelope of the swift. The upper surface corrugation of swift hand wings resembles the corrugation of dragonfly airfoils, but is concentrated towards the leading edge and has a 5-10 times smaller amplitude (Kesel, 2000;Jongerius and Lentink, 2010;Lentink and de Kat, 2014). Corrugated dragonfly airfoils also generate laminar separation bubbles in the valleys formed by the corrugation (Rees, 1975a;Buckholz, 1986;Lentink and Gerritsma, 2003;Vargas and Mittal, 2004;Kim et al, 2009;Seifert, 2009, 2010;Murphy and Hu, 2010;Hord and Liang, 2012); such effects of corrugation have not been demonstrated before in birds (Elimelech and Ellington, 2013).…”

3D reconstruction and analysis of wing deformation in free-flying dragonflies

“…It is considerably more practical to measure the mesosurface of a static insect wing (Jongerius and Lentink, 2010;Tsuyuki et al, 2006). Thus, our approach is to build on this work in order to model the surface corrugation of reconstructed free-flying insect wings.…”

“…Laser scanning was used to measure the surface roughness of severed insect wings (Tsuyuki et al, 2006). The structure of a dragonfly forewing and hindwing were studied by scanning them with a micro-CT scanner (Jongerius and Lentink, 2010). Corrugation in flapping insect wings was also studied (Walker et al, 2009a).…”

Learning from Nature: Unsteady Flow Physics in Bioinspired Flapping Flight

“…Laser scanning was used to measure the surface roughness of severed insect wings [47]. Dragonfly forewing and hindwing structures have been studied using a micro-CT scanner [48]. Corrugation in insect wings, for example, locust wings, has also been investigated [44].…”