Resonance mechanism of flapping wing based on fluid structure interaction simulation

Abstract

Certain insect species have been observed to exploit the resonance mechanism of their wings. In order to achieve resonance and optimize aerodynamic performance, the conventional approach is to set the flapping frequency of flexible wings based on the Traditional Structural Modal (TSM) analysis. However, there exists controversy among researchers regarding the relationship between frequency and aerodynamic performance. Recognizing that the structural response of wings can be influenced by the surrounding air vibrations, an analysis known as Acoustic Structure Interaction Modal (ASIM) is introduced to calculate the resonant frequency. In this study, Fluid Structure Interaction (FSI) simulations are employed to investigate the aerodynamic performance of flapping wings at modal frequencies derived from both TSM and ASIM analyses. The performance is evaluated for various mass ratios and frequency ratios, and the findings indicate that the deformation and changes in vortex structure exhibit similarities at mass ratios that yield the highest aerodynamic performance. Notably, the flapping frequency associated with the maximum time-averaged vertical force coefficient at each mass ratio closely aligns with the ASIM frequency, as does the frequency corresponding to maximum efficiency. Thus, the ASIM analysis can provide an effective means for predicting the optimal flapping frequency for flexible wings. Furthermore, it enables the prediction that flexible wings with varying mass ratios will exhibit similar deformation and vortex structure changes. This paper offers a fresh perspective on the ongoing debate concerning the resonance mechanism of Flexible Flapping Wings (FFWs) and proposes an effective methodology for predicting their aerodynamic performance.