Formation effects on the group propulsion performance of manta rays

Based on the establishment of morphological models and kinematic equations with high biosimilarity, a numerical calculation method of bionic group hydrodynamics based on the immersed boundary method is proposed, and a numerical study of group hydrodynamics of manta rays in tandem, positive triangle, and inverted triangle formations is carried out. The results show that in a tandem formation, manta rays at the head of the line gain hydrodynamic benefits only when the row spacing is small, and that the propulsive performance of manta rays in the middle of the line is the best, and that it directly determines the propulsive performance of the group system. In the two triangular formations, the hydrodynamic performance is both somewhat similar and somewhat unique. The similarities are that the propulsive performance of leader manta rays decreases significantly and the followers' propulsive performance fluctuates according to the spacing in both formations, while the uniqueness is that the followers' propulsive efficiency increases in the inverted triangle formation. The conclusions can provide recommendations for formation and spacing decisions for multi-bionic underwater vehicles performing cluster missions in the same plane.