Research on the hydrodynamic performance of double manta ray gliding in groups with variable attack angles

To investigate the effect of arrangement and attack angle on the hydrodynamic performance of double manta rays in group gliding, a manta ray model was first established based on the actual shape of manta rays, and then, numerical simulations were carried out with Fluent software to simulate the group gliding of double manta rays in three arrangements of tandem, parallel, and vertical with variable attack angle and variable spacing. Then, the average lift/drag of the group system and the lift/drag of each individual in the group were analyzed by combining with the flow field pressure cloud. From the drag performance, a systematic drag reduction was observed for the double manta rays in tandem and parallel group gliding; in vertical cluster gliding, with the change of attack angle, the individual in the group alternately gained drag reduction, but no systematic drag reduction was found. In terms of lift performance, the average system lift is basically the same as that received by the single body when gliding, regardless of the arrangement, and the difference in lift received by each individual in the group decreases with the increase in the arrangement spacing. This study provides useful results for the formation arrangement of group gliding with twin underwater vehicles.