Hydrodynamic Interactions in Schooling Fish: Prioritizing Real Fish Kinematics Over Travelling-Wavy Undulation

Hydrodynamic interactions are crucial for un- derstanding fish movement, particularly within the realm of robotic applications. Traditionally, many studies have favoured simplified travelling-wavy undulations derived from observed real fish kinematics. This approach often neglects higher-order undulations, thereby missing the subtleties of authentic fish movements. In this study, we utilised Computational Fluid Dynamics (CFD) to investigate the implications of using real fish kinematics in hydrodynamic interactions among schooling fish. We analysed two scenarios: one driven by real fish kinematics in spatiotemporal formations, and the other by travelling-wavy undulations inferred from the same real fish kinematics. Our results highlight the advantages of using real fish body kine- matics for a more accurate representation of hydrodynamics in fish swimming. In contrast, the idealised travelling-wavy undulations tend to apply excessive force, displacing real fish more than expected. Additionally, the vortices and correspond- ing flow fields generated by real fish kinematics were found to be more stable than those arising from simplified travelling- wavy undulations. Our study underscores the significance of integrating real fish kinematics into robotic fish design and hydrodynamic studies in schooling fish.