Abstract: A conceptual design of bionic Autonomous Underwater Glider (AUG) is introduced, with a pair of flapping wings. The immersed boundary method is employed and Navier–Stokes equations are solved to investigate the propulsive performance of the bionic AUG with Aspect Ratios (ARs) of the flapping wings varying from 0.36 to 5. The propulsive efficiency of the whole AUG is newly defined, in contrast to the definition of single flapping wing. The numerical results show that the thrust of flapping wings increases due to the wing-fuselage interaction. The thrust coefficient of the flapping wings increases as the AR increases. The propulsive efficiency of the AUG increases first and then decreases as the AR increases. There is an optimum AR leading to the highest propulsive efficiency, which is different from the result of the single wing case. To balance the advancing speed and gliding endurance, the AR of the flapping wing is recommended to be set as the optimum value of around 0.60. The vortex structures in the wake of the AUG with different ARs are also presented and compared.

Key words: Autonomous Underwater Glider (AUG), bionic propulsion, flapping wing, Aspect Ratio (AR) effect