Oscillating Performance and Fluid-structure Interaction Mechanism of a Small Koi's Caudal Fin-like Underwater Propulsion Actuated by MFC

Macro fiber composite(MFC) exhibits significant advantages of high actuation stress, large flexibility and excellent waterproof performance, compared with conventional piezoelectric ceramics. Thus, MFC actuators have great potentials in the applications of bio-inspired locomotion and flexible actuation. Mimicking the morphological characteristics and body or caudal fin(BCF) locomotion mode of koi fishes, a small koi's caudal fin-like underwater propulsion is designed and fabricated. Experimental results show the maximum underwater oscillating velocity of the propulsion is 154.5 mm/s, with the Peak-to-Peak actuation of 1 000 V, at 7.5 Hz. Computational fluid dynamic(CFD) analyses are conducted to investigate the flow structure caused by the oscillating propulsion. Simulation results show the mean and maximum instantaneous thrust generated by the propulsion in the stable-state are 4.22 m N and 9.8 m N, respectively, which matches well with the Lighthill's slender body theory. A high-velocity flow region is noti