Hydrodynamic forces and efficiency of a swimming body

Swimming motion of fish has long been a central topic of research in biomimetic mechanics. Fish employ various swimming modes, including anguilliform, carangiform, and ostraciiform motions. Many studies have investigated the effects of different Reynolds and Strouhal numbers by varying swimming frequency, wave number, and amplitude to optimize oscillation patterns and identify the most efficient swimming mode. In this study, NACA0012 airfoil is used to model the body shape and simulate swimming in anguilliform motion. The dynamic mesh technique in OpenFOAM is applied to solve the two-dimensional Navier-Stokes equations using finite volume method. This simulation aims to predict the most energy-efficient swimming mode for fish under cruising conditions. We explore different oscillation frequency and amplitude, the optimal swimming mode can be determined. In our simulations, a moving reference frame is attached to the fish body and drag is calculated, while quasi-propulsive efficiency is also calculated to identify the optimal swimming method. The results show that higher amplitude body movements produce greater propulsion; however, from an energy efficiency standpoint, such movements may not represent the most effective swimming mode.