Research on swimming performance of fish in different species

Manta rays and tunas are outstanding representatives of propulsion by MPF (median and/or paired fin) and BCF (body and/or caudal fin), respectively, and it is an interesting topic to see what kind of fluid effects will be generated when they meet during the swimming process. In the present study, numerical simulations were performed for the individual swimming state of manta ray/tuna and the group swimming of manta ray and tuna in a tandem arrangement. In individual swimming conditions, increasing amplitude helps to improve manta ray thrust and increasing wave number helps to improve manta ray efficiency; increasing frequency, tuna thrust increases monotonically and efficiency increases first and then decreases. In the tandem group swimming state, the manta ray thrust and efficiency are enhanced at most spacings, the smaller the spacing, the greater the enhancement, as seen in the vortex structure, which benefits from the merging of the rear tuna wake. The thrust and efficiency curves of the tuna fluctuate greatly with spacing, which is related to the position of the manta ray wake field where the tuna are located.