Oscillating performance and propulsion mechanism of biomimetic underwater oscillatory propulsion by resonant actuation of macro fiber composites

Abstract

An oscillatory propulsion driven by the resonant actuation of macro fiber composites is proposed. Specifically, the propulsion is modeled as a cantilever internally actuated by bonded macro fiber composite actuators, with a passive attachment. Underwater oscillating performances of the proposed device are investigated experimentally. Experimental results show that the maximum oscillating magnitude and velocity of the propulsion are 4.20 mm and 163.5 mm/s. Computational fluid dynamic simulations for the formation of the vortices caused by the oscillating structure are conducted. The maximum instantaneous and mean thrusts of the propulsion in the stable periods are 4.72 mN and 1.87 mN, respectively. The initiation, development, separation, and propagation stages of the vortex caused by the oscillating structure are revealed. The phenomenon of the reverse Karman vortex street is observed. The location and distribution of the vortices are also indicated. A high-velocity region between the neighboring counterrotating vortices is detected from the cycle-averaged velocity fields. The maximum flow velocity in the region is approximately 1.5 times the oscillating velocity of the propulsion. Furthermore, a jet, resembled by the flow, ejects from the propulsion tip and spreads out backwards. The propulsion travels forward by the reaction force of the pseudo-jet. Those results may be helpful for the studies on biomimetic underwater propulsion devices.