Numerical simulation of self-propulsion performance of dolphins at high Reynolds numbers

In this paper, a numerical simulation is conducted to investigate the self-propulsion process of dolphins at a maximum Reynolds number of 3.5 × 10 6 . The flexible deformation and overall self-propulsion of dolphins are achieved by employing dynamic mesh and overset mesh technique. This study systematically analyzes the effects of parameters, including traveling wave length, traveling wave frequency, and incoming flow velocity, on the propulsion performance of dolphins. The simulation results indicate that the average forward velocity of dolphins approximately exhibits a logarithmic relationship with the traveling wave length, while it approximately follows a linear correlation with the traveling wave frequency and incoming flow velocity. Specific fitting functions are provided in this paper, and this conclusion holds significant guiding value for the development and commissioning of subsequent bionic prototypes. Regarding propulsion efficiency, as the traveling wave length and traveling wave frequency increase, the propulsion efficiency first increases and then decreases, with optimal motion parameters corresponding to the maximum efficiency; the respective optimal parameters are λ * = 1.0 and f = 1.5 Hz. For the incoming flow velocity, the forward efficiency of dolphins gradually decreases with the increase of incoming flow velocity, which is mainly attributed to the increased energy consumed to resist the impact of the incoming flow. Finally, this paper analyzes the flow field structure under typical operating conditions and preliminarily explores the internal mechanism of the dolphins' high-efficiency propulsion from the perspectives of the evolution of the vortex structures in the wake of flow field and the pressure variation on the dolphin's surface.