Study of lift enhancing mechanisms via comparison of the flapping trajectory of tandem flapping foil

Designing an aero/hydrovehicle that mimics natural swimmers such as fish is a challenging task. In the present study, an attempt has been made to mimic the fish tail motion that generates the lift energy. Two fishtail trajectories are replaced with two National Advisory Committee for Aeronautics 0012 foils in a tandem configuration for energy extraction. The energy induced due to lift force of the hind wing while flapping along fishtailed trajectory in single and tandem configurations is determined and compared with that of the simple flapping foil having heave and pitch motion only. The impact of various factors such as foil gap (G), phase angle (φ), and influence of Strouhal number (St) on the energy extraction performance is also investigated at a Reynolds (Re) number of 1173. The results show that a fishtail motion trajectory and foil gap ratio of 3c–4c (c being chord length) would enhance the energy extraction performance of the hindwing. The present research provides a new vision for the improvement of biomimetic power generators, as it aims to improve energy efficiency through the use of wake vortices.