Whole swimming process of manta ray–like vehicles with different flapping parameters

To investigate the effects of different flapping parameters on the swimming process of a manta ray–like vehicle, a morphology model and equations of deformation for the biomimetic vehicle were established, and a two degree–of-freedom self-propelled simulation strategy coupling kinematics and hydrodynamics was developed. Subsequently, the impacts of different flapping frequencies (f) and amplitudes (A) on the kinematics, hydrodynamics, and vortex structure evolution of the vehicle were explored. The results of our study are mentioned below: an increasing A effectively enhanced the thrust and accelerated the performance via the accumulation of shear layers. The thrust with the A = 0.4 is 179.7% higher than that with the A = 0.25. Compared with f reduction, A reduction decreases the spanwise vorticity of the fin-tip vortex (TV) and trailing-edge vortex (TEV) while increasing the streamwise vorticity. Reducing f decreases the spanwise and streamwise vorticity of the TEV and TV, thereby significantly reducing energy dissipation. A lower f is highly suitable for energy-efficient long-distance swimming. Compared with the f = 1.0, the f = 0.5 increases the travel distance by 351% while consuming the same energy. This study revealed the influence and underlying mechanisms of different flapping parameters on a bionic vehicle, providing a reference for their efficient control.