Vortex Phase Matching for Energy Efficiency Enhancement in Staggered Formations of Manta Ray-inspired AUVs

Bioinspired underwater vehicles offer broad application prospects in ocean development and underwater operations due to their high propulsion efficiency and excellent maneuverability. However, individual vehicles often face limitations related to energy density and task payload when operating in complex environments. Swarm coordination is considered an effective approach to enhancing operational efficiency and energy performance. In this study, a dual-vehicle experimental platform composed of two manta ray-inspired flexible pectoral fin prototypes was developed to investigate the hydrodynamic interaction during collective swimming. The experiments were conducted with fixed vertical spacing (Dz) and variable streamwise spacing (Dx) ranging from 0 to 1.0 body lengths (BL). Results show that the leader generally outperforms solo swimming, and both the individual and system-level hydrodynamic performances reach their peak at Dx = 0.4BL. At this spacing, the leader's maximum thrust and efficiency increase by 13.31% and 18.58%, respectively, while the follower achieves maximum improvements of 24.51% in thrust and 38.36% in efficiency. The overall system efficiency is enhanced by up to 28.47%. These findings demonstrate the significant impact of spatial arrangement on propulsion performance and provide experimental evidence to support energy-efficient control and adaptive formation strategies in underwater robotic swarms.