Abstract
Fish have evolved the ability to swim with high speed, efficiency, and maneuverability and have developed specialized locomotion strategies to most efficiently interact with the surrounding fluid environment. They also leverage collective behavior via schooling to allow for better hydrodynamic performance. The undulatory motion, irregular morphologies, and strong hydrodynamic interactions from schooling create a complex fluid environment where high performance can be achieved. This research is a systematic study of large schooling effects and morphology in fish and fish-like robots. A Cartesian grid-based immersed boundary incompressible Navier-Stokes solver is used to simulate the unsteady flow around fish-like swimmers. The study begins by evaluating a 2D swimmer in planar arrangements of large, dense fish schools. A comparison of the arrangements concludes that diamond schools balance the higher thrust benefits from longer schools with the power savings from wider schools and allow for a high-performance school with more evenly distributed performance benefits. Additionally, within the context of these dense schools, synchronous motion between fish allows for the most constructive body-body pressure interactions throughout the school and maximizes performance gained from schooling. Classification of individual fish within the school persists as a performance and interaction predictor through each arrangement and size of the school. Interactions between multiple schools of fish are also studied. This is done via numerical simulations of multiple diamond fish schools swimming in line. The wake interaction provides a significant opportunity for performance benefits in the follower subschool but can also be a detriment with different vortex interactions resulting from altered spacing between subschools. Finally, morphological effects in schools of undulating swimmers are studied. Simulations begin with a single tuna-inspired robotic platform swimming. Propulsor crosssectional shape, body thickness, kinematic effects, and median fin design are varied. Next, more fundamental shape parameters are varied using a class shape transformation method to generate undulating body shapes in both 2D and 3D. The impact of body shape is observed in single and schooled swimmers. This study shows that variations in body shape, particularly in the posterior region of the body, have a significant impact on the performance of solo and schooling swimmers. The primary contributions of this dissertation are in the characterization of large fish schools, including the classification of individuals, characterization of performance enhancing mechanisms of interaction, understanding of arrangements for high performance, and morphological impacts on schooling interactions. The findings from this work will bring new insights into the future design of bio-inspired unmanned underwater vehicles.
