Aerodynamic consequences of wing damage in dragonflies

Flapping wings are the primary means by which dragonflies generate forces, but they are susceptible to damage due to their inherent fragility. The damage results in a reduction in wing area and a distortion of the original wing, which in turn leads to a decline in flight ability. Furthermore, the flows of dragonfly fore- and hindwings exhibit an interaction, thus damage to the forewing can also impact the aerodynamic performance of the ipsilateral hindwing. In this study, we examine this problem through CFD (computational fluid dynamics) simulations on a series of damaged dragonfly fore-/hindwing models according to the probability of area loss from the literature. The flow fields and aerodynamic forces for the different damaged wing cases are compared with those for the intact wings. This comparative analysis reveals how the different patterns of wing damage modify the vortex structures around the flapping wings and lead to a drop in aerodynamic force production. The causes behind the diminishing aerodynamic performance are shown to be subtler than the pure area loss and are regulated by the changes in the flow field that result from wing damage. Wing-wing interaction becomes particularly important when forewing damage occurs.

💡 Research Summary

This paper investigates how wing damage affects the aerodynamic performance of dragonflies, focusing on the interaction between the fore‑ and hind‑wings. Using probability maps of wing‑area loss derived from a field study of wild Sympetrum vulgatum, the authors generated five levels of damage for both fore‑ and hind‑wings (FW1‑FW5 and HW1‑HW5). The base geometry and kinematics were taken from Pantala flavescens, with flat, rigid wings and a fixed flapping pattern (positional angle φ, feathering angle α, stroke angle η). The Reynolds number based on mean tip velocity and chord is 1 288, placing the flow in the low‑to‑moderate regime where unsteady vortex dynamics dominate.

Computational fluid dynamics were performed with an in‑house solver (WABBIT) that couples an immersed‑boundary method with wavelet‑based adaptive meshing, solving the full Navier–Stokes equations without turbulence modeling. The numerical wind‑tunnel is a 10 × 10 × 10 domain; the insect is held stationary while a free‑stream velocity simulates forward climbing flight. For each damage case the same flapping kinematics were retained, allowing a pure assessment of geometric loss.

Results show that aerodynamic force and power coefficients decline with increasing wing‑area loss, but the relationship is highly non‑linear and strongly dependent on where the loss occurs. Damage near the wing tip (especially on the fore‑wing) disrupts the leading‑edge vortex (LEV) and tip vortex (TV), causing a sharp drop in vertical force during the downstroke and a reduction in thrust during the upstroke. Conversely, loss concentrated on the trailing edge has a milder effect because those regions contribute less to lift generation.

A key finding is that fore‑wing damage influences the hind‑wing’s aerodynamics through altered vortex interaction. In the most severely damaged fore‑wing case (FW5), the tip vortex is broken near the damaged region, shifting its interaction with the hind‑wing toward the wing root. This modifies the pressure field around the abdomen and reduces the hind‑wing’s contribution to thrust, even though the hind‑wing itself remains intact. When the hind‑wing is damaged (HW5), the fore‑wing’s tip vortex passes unimpeded, but the hind‑wing’s own vortex is weakened, diminishing its ability to generate lift and thrust and reducing the overall power output.

Force coefficient analysis reveals that the fore‑wing primarily contributes drag (negative horizontal force) while the hind‑wing supplies the majority of thrust. Consequently, fore‑wing damage can slightly increase the net horizontal force because the drag component is reduced, but the overall vertical force and power drop dramatically. The authors also compute force‑per‑unit‑area ratios, showing that tip‑region loss yields a much larger decrease in performance per lost area than loss near the root.

Visualization of Q‑criterion iso‑surfaces confirms that vortex structures on the undamaged side remain essentially unchanged, indicating that damage effects are localized but propagate through wing‑wing coupling. The study therefore concludes that aerodynamic penalties from wing damage arise not merely from reduced planform area but from complex alterations in unsteady vortex dynamics and inter‑wing interactions.

These insights have ecological relevance—damaged dragonflies experience reduced flight capability, affecting prey capture and predator evasion—and engineering implications for bio‑inspired micro‑air vehicles, suggesting that preserving tip integrity and fore‑wing structure is critical for maintaining performance under damage.