Numerical comparison between symmetric and asymmetric flapping wing in tandem configuration

Abstract

Dragonflies show impressive flight performance due to their unique tandem flapping wing configuration. While previous studies focused on forewing-hindwing interference in dragonfly-like flapping wings, few have explored the role of asymmetric pitching angle in tandem flapping wings. This paper compares the aerodynamic performance of asymmetric dragonfly-like wings with symmetric hummingbird-like wings, both arranged in tandem. Using a three-dimensional numerical model, we analyzed wing configurations with single/tandem wings, advance ratios (J) from 0 to 0.45, and forewing-hindwing phase differences (ϕ) from 0° to 180° at a Reynolds number of 7000. Results show that asymmetric flapping wings exhibit higher vertical force and flight efficiency in both single and tandem wing configurations. Increasing the phase difference (ϕ) improves flight efficiency with minimal loss of vertical force in the asymmetric flapping mode, while the symmetrical flapping mode significantly reduces vertical force at a 180° phase difference. Additionally, symmetric tandem flapping wings unexpectedly gain extra vertical force during in-phase flapping. This study uncovers the flow characteristics of dragonfly-like tandem flapping wings, providing a theoretical basis for the design of tandem flapping wing robots.