Numerical investigation on novel conceptual design of hybrid-driven autonomous underwater glider with active twin flapping foils

Abstract

A novel conceptual design of hybrid-driven autonomous underwater glider (AUG) is proposed to help the AUG increase gliding speed. The twin hydrofoils of AUG will undergoes flapping motion, just like the fish fins or bird wings, when the AUG encounter severe sea conditions while remain stationary at other times. The motion parameters of flapping foil needs to be adjusted to satisfy the force balance condition thus the AUG may achieve cruise status under constant moving velocity. The numerical simulation has been conducted to investigate the hydrodynamic performance of current AUG by using of the immersed boundary method under different incoming velocities. The numerical result shows that there exists optimum dimensionless St number, as a combination of heaving amplitude, flapping frequency and incoming velocity, resulting in highest propulsive efficiency and there exists mutual linear relationship between three motion parameters. The vortex ring structures at the rear part of the AUG under three typical St numbers are also presented and discussed, proving qualitative explanation for the numerical results. The conclusion acquired in this study may provide technical guidance for the development of hybrid-driven unmanned underwater vehicle (UUV).