Cyber-physical experiments on the efficiency of swimming protocols

We present results from experiments on a biologically inspired cyber-physical system, composed of a two-dimensional heaving and pitching rigid airfoil attached to a six component load cell, mounted to a traverse that can move along a water channel. A feedback controller, influenced by the apparatus of Mackowski and Williamson (J. Fluid Struct., 2011), introduces the effects of a fictional drag force specified by a virtual body profile and drives the traverse accordingly. Free-swimming protocols using the force-feedback system are compared with similar motions on a motionless traverse. The propulsive efficiency of burst-and-coast kinematics is also considered. Of particular interest are (1) the implementation of the cyber-physical control system with respect to the accessible experimental parameter space, (2) the impact of force-based streamwise actuation on experimental data, and (3) the effects of burst-and-coast motions on propulsive efficiency.