Locomotion of a flexible plate: How the boundary condition of the leading edge affects the self-propulsion performance

Abstract

In the nature, the fish can control the wave propagation on the caudal fin using the sarcomere at the leading edge of the caudal fin. The control methods can be classified into three modes: Active Heave and Active Pitch (AHAP),Passive Heave and Active Pitch (PHAP), Active Heave and Passive Pitch (AHPP). Which mode can produce the largest thrust? Which mode can develop the most efficient swimming performance? So far, the research on these issues still cannot be found in the article. In this paper, we have studied the self-propulsion of the flexible plates driven by these three modes. It is expected that results can shed new light on understanding the locomotion mechanism of the fish and give a new idea for the design and control of the robot fish. The vibration of the flexible plate in the high velocity flow maybe unstable, and the velocity threshold of the flow are depending on the stiffness of the plate. The motion of the plate driven by AHAP is the most unstable, while AHPP is the most stable driving mode. The thrust on the flexible plate is mainly affected by the resonance effect, and the thrust in AHAP mode and AHPP mode are larger than that in PHAP mode. The propulsive efficiency is affected by both the resonance effect and the phase dynamics in the oscillator model. The phase dynamics is the dominant factor, and the resonance effect is the secondary factor.