Experimental Investigation of Impulsive Motions of Flapping Foils to Produce Large, Transient Lift and Thrust Forces*

As underwater vehicles become increasingly versatile and capable, bio-inspired propulsion systems are becoming a viable possibility for future vehicles. In particular, flapping foil actuators are promising in their abilities for propulsion and maneuvering. Current underwater vehicles rely on propellers, which form a jet wake to produce propulsion forces, and as such, experience an inherent delay between the movement of the propeller and the vehicle feeling a propulsive force. To mitigate this shortcoming, flapping foils were tested to produce large, transient forces in still water. These swift, one-time strokes take advantage of added mass/inertial effects and large, stably attached vortices to produce propulsive forces almost instantaneously. Various trajectories in heave and pitch were tested and analyzed to compare to previous work. Further work includes optimizing the trajectory to produce the desired propulsion forces for vehicle control and maneuvering.