Understanding swimming hydrodynamics of elastic propulsors with tapered thickness

鱼利用灵活的鳍实现快速高效的游泳，远远超过目前人造设备的性能。本计算研究项目旨在研究鳍弹性在水下运动中的作用，并了解厚度渐变对鳍游动性能的影响。鱼鳍和鱼鳍通常具有逐渐变薄的厚度，从鳍底部到后缘，鳍的厚度逐渐减小。据推测，这种几何特征有助于提高鳍的游动性能，但厚度渐变如何有助于提高鳍的性能在很大程度上尚不清楚。本项目将利用计算机模拟的方法来研究锥形厚度的俯冲式弹性鳍在水下的运动，以揭示和分析其最大限度地推进和提高游泳效率的水动力机制。该项目的研究成果将有助于开发新型的具有高效仿生鳍的游泳机器人。这种自主机器人可能在各种水下应用中有用，包括监视、救援行动、水污染控制和鱼类监测。这项拟议的计算研究旨在加深对使用锥形厚度弹性平板推进器在粘性流体中波动游泳的流体动力学的基本理解。该项目假设，厚度渐变会导致声波黑洞效应，从而抑制弯曲波在推进器尾缘的反射，这反过来又有助于形成更有效的水下运动行波。它进一步假设，厚度缩减可以用来控制推进器的弯曲模式和推进器产生的弯曲波的类型。该项目将使用流体-结构相互作用的三维计算模型来研究项目假设，并描述不同流动条件下锥形推进器的流体力学特性。它将试图了解行波和驻波对仿生运动的影响，并确定促进高效和快速游泳的水动力学机制。该项目将确定这些流体动力机制如何依赖于推进器的几何形状和特性。进化遗传算法将被用来识别导致最佳推进的锥形。该项目的成果将促进对非定常粘性流动和非均匀厚度的振动弹性板之间复杂相互作用的基础知识，从而使开发用于高效水下运动的新型仿生推进器成为可能。该奖项反映了NSF的法定使命，并通过使用基金会的智力优势和更广泛的影响审查标准进行评估，被认为值得支持。

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.