Visualization on vortical structures in the wake of a pair of pitching wings with asymmetrical motion

Constructive foil-wake Interactions of tandem flapping hydrofoils for propulsion and energy harvesting

“…For forward flight, asymmetric motions could vary the instantaneous force production, which may affect the flight capabilities. Recently, Liu et al [67] visualized the unsteady flow structures generated by two foils with asymmetric pitching motions in a biplane configuration using the laser-induced fluorescence method (LIF) and the finite-time Lyapunov exponents (FTLE) method. Based on their results, the stroke time-asymmetry was proved to be a critical kinematic parameter influencing wake turbulence by introducing jet-like behaviors for thrust production.…”