Parametric analysis on the acoustic characteristics generated by a biomimetic swimmer

Abstract

Previous studies have shown the excellent hydrodynamic performance of fish swimming. However, the main factors that lead to the low-noise propulsion of fish are still unrevealed. In this study, numerical studies on the characteristics of the far-field sound generated by a bio-inspired swimmer were carried out. The model was simplified as a two-dimension (2D) foil based on the numerous analyses in the past decades. The effects of propulsion methods, model thickness, Strouhal number St, and Reynolds number Re on the flow-induced sound were analysed. Reynolds-Averaged Navier–Stokes (RANS) and Ffowcs Williams–Hawkings (FW–H) equations were employed to simulate the fluid field and the acoustic characteristics, respectively. Simulation results indicated that the sound distribution generated by the biomimetic swimmer exhibits a dipole-like pattern. It was noted that by analysing the effect of motion wavelength on the effective sound pressure, an anguilliform swimmer generates lower sound during propulsion than swimmers with other types of motions. With a small thickness-length ratio, the bio-inspired swimmer could generate large thrust but small sound. Meanwhile, the maximum effective sound pressure is related to the effective lift of the foil.