Propulsive efficiency of a pitching foil with trailing edge control*

A series of experiments conducted with a robotic fin, demonstrate how by actuating its trailing edge while performing periodic flapping, enhanced efficiencies and thrusts can be achieved depending on the phase difference imposed between the motions.

The robotic fin consists of a rigid 3D printed panel in which the trailing edge is articulated. The fin is controlled by two independent servos that actuate the fin and its trailing edge independently. Measurements include forces and moments acting on the fin whilst flapping, as well as the torque applied to the shaft. The flow dynamics around the fin was also measured using planar Particle Image Velocimetry.

Results show how the phase difference between the trailing edge and the fin is a key parameter, and how only when the trailing edge moves behind the fin not only thrust is enhanced but efficiency as well.