Fig. 10. Digital particle image velocimetry (DPIV) results for the robotic ribbon fin at three different time instances. The ribbon fin is shown in translucent gray. The colormap indicates the x-velocity normalized by the wave speed V. In this case V=0.5 m s^–1. (A) DPIV image and computed flow field at t=2.67 s (after four complete wave cycles). (B1), (B2) and (B3) flow field for the robotic ribbon fin at t=2.67, 2.80 and 3.00 s, respectively, equivalent to 0, 20 and 50% of one wave cycle. Velocity values at and above 50% of the wave speed are mapped to red to highlight the streamwise jet, which includes velocities as high as 90% of the wave speed.