Aerodynamic characterization of dragonfly-like flexible flapping wing during forward flight

Purpose This study aims to investigate the aerodynamic effects of different spanwise flexibility distributions in dragonfly-inspired flapping wings, focusing on vein stiffness variation. Design/methodology/approach A 3D bio-inspired forewing model with leading-edge vein, cross-veins and membrane is developed. Uniform, linear, parabolic and logarithmic vein flexibility distributions are implemented. Aerodynamic responses under different inflow velocities and pitch amplitudes are analyzed using a fluid–structure interaction framework. Findings Non-uniform vein flexibility significantly enhances aerodynamic performance compared to uniform flexibility. In particular, logarithmic distribution produces stronger vortex accumulation, slower shedding and larger pressure differences, yielding higher peak lift. It also forms a more regular anti-Kármán vortex street with stronger trailing-edge vorticity, leading to increased peak thrust and longer thrust duration. Practical implications The results provide guidance for optimizing vein flexibility distributions in micro flapping-wing aerial vehicles. Originality/value This work firstly systematically compares multiple spanwise vein flexibility distributions, highlighting the superiority of logarithmic patterns in enhancing lift and thrust.