Dynamic mode decomposition for unsteady flow over flapping wings

Miniature crafts with flapping wings exploit dynamic stall to produce enhanced lift while flying in outdoor conditions, which will be required to not only perform robustly when encountering freestream perturbations but also to be capable of producing rapid changes in aerodynamic force during voluntary aerial manoeuvres. In order to systematically study the effects of freestream perturbations on dynamic stall of flapping wings, an in-house immersed boundary-lattice Boltzmann method fluid-structure interaction (FSI) solver is developed. The FSI solver is used to generate large flowfield datasets for dynamic mode decomposition (DMD) to identify key modes that govern the flow dynamics. In this study, the code validation of the FSI solver is performed by simulating the pitching and plunging motions of a two-dimensional rigid NACA0015 foil in uniform flow. Good agreement of results between current computations and published data are observed, suggesting that the solver can accurately compute the flapping wing systems. Results of the DMD performed for flow over a stationary cylinder agree well with the published data. Results and DMD analysis of flapping wings will be presented and discussed in the full paper.