Optimization of start-up propulsive efficiency and schooling behavior of thunniform swimmers in diamond and phalanx fish schools

Optimal fish array hydrodynamics in accelerating thunniform fish schools are investigated through a computational framework which combines high fidelity Computational Fluid Dynamics simulations with a surrogate-based black-box optimization algorithm. Several factors relevant to fish schooling, such as the school shape, separation distance, midline kinematics and phase synchronization, are used to investigate the hydrodynamic properties of group swimming associated with the maximum propulsion efficiency. The results show that both the diamond and phalanx school formations can provide hydrodynamic benefits over solitary swimming during acceleration. Furthermore, a breakdown of the useful propulsive energy gained versus the total energy input of a school reveals multiple distinct schooling regimes, based on several schooling parameters, where one quantity is favored over the other for both the diamond and phalanx formations.