Understanding swimming hydrodynamics of elastic propulsors with tapered thickness

Georgia Tech Research Corporation, Atlanta GA

Investigators

Abstract

Fish leverage flexible fins to achieve fast and efficient swimming that far exceeds the performance of current man-made devices. This computational research project aims to investigate the role that fin elasticity plays in underwater locomotion and to understand the effects of thickness tapering on the fin swimming performance. Fish fins and rays typically feature tapered thickness where the fin thickness gradually decreases from the fin base to the trailing edge. It is speculated that this geometrical feature can be beneficial for enhancing fin swimming performance, however how the thickness tapering contributes to enhanced performance of fins remains largely unknown. This project will use computer simulations to probe the underwater locomotion of plunging elastic fins with tapered thickness to reveal and analyze the hydrodynamic mechanisms maximizing their swimming propulsion and efficiency. The results of this project will facilitate the development of novel swimming robots with efficient biomimetic fins. Such autonomous robots may be useful in diverse underwater applications, including surveillance, rescue operations, water pollution control, and fish monitoring. The proposed computational research aims to develop fundamental understanding of the hydrodynamics of undulatory swimming in viscous fluids using elastic plate propulsors with tapered thickness. The project hypothesizes that thickness tapering causes the acoustic black hole effect that suppresses the reflection of flexural waves at the trailing edge of the propulsor, which in turn facilitates the formation of more efficient for underwater locomotion traveling waves. It further hypothesizes that thickness tapering can be used to control the propulsor bending pattern and the type of flexural waves the propulsor produces. The project will use a three-dimensional computational model for fluid-structure interactions to investigate the project hypotheses and to characterize the hydrodynamics of tapered propulsors at different flow conditions. It will seek to understand the effects of traveling and standing waves on biomimetic locomotion and to identify hydrodynamic mechanisms facilitating the efficient and fast swimming. The project will establish how these hydrodynamic mechanisms depend on the propulsor geometry and properties. An evolutionary genetic algorithm will be harnessed to identify the tapering shapes leading to the optimum propulsion. The results of this project will advance the fundamental knowledge of the complex interactions between unsteady viscous flows and oscillating elastic plates with nonuniform thickness, thereby enabling the development of novel biomimetic propulsors for efficient underwater locomotion. This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.