Flow Physics and Vortex-Induced Acoustics in Bio-Inspired Collective Locomotion

学校教育现象在自然界中无处不在。其突出的例子包括成群的鱼，以特定队形飞行的鸟类，以及小范围生物物体的集体运动，如精子。这样的配置有助于成员显著降低推进的能量成本，并增强其推力和效率。在这些自然动力系统中，由于每个学派成员的波动运动学，出现了高度不稳定的三维涡旋。由于相干结构与在其附近运动的物体的相互作用，它变得更加复杂。此外，这些活动会在周围流体中产生压力扰动，导致声波信号在水中传播。这篇序言为我在计算流体-结构-声学相互作用(FSAI)和仿生机器人领域建立和发展我的研究生涯提供了基础，这支持了我开发下一代高速、高效和隐形的自然启发机器人的长期研究目标。目前提出的研究集中在开发一种新的计算求解器，通过尖锐界面浸没边界方法来处理涉及多个振动体的强烈的流固耦合作用。此外，该求解器便于提取和分析相干流动结构，以确定它们在产生非定常力方面的作用。该方法将大大有助于开发不同的自然游泳运动员和他们的学校配置的准确的理论和计算模型。了解鱼类通过周围水流中的压力信号进行交流的机制也特别相关，这使它们能够感觉到其他移动物体的存在，并充当导航工具。为此，我将开发模块来计算数值求解器中的声学特征，以了解涡体相互作用如何影响流场中压力扰动的发射。这项工作对于建立设计能够在不破坏自然栖息地的情况下静静游泳的自主式鱼类机器人的原则非常重要。除了仿生机器人和能源收割机，通过这项研究获得的基本知识和在该计划中开发的新型计算工具的应用是跨学科的。其中包括各种与FSAI相关的生物机制的检查，不同物体在环境流动中的动力学，以及工程系统在环境中的声发射。除了在多学科领域培训HQP外，该项目还将为高中物理专业的学生开发流体动力学教育模块，并为年轻妇女和土著人民开展各种外联活动，以激励他们了解STEM。

Schooling phenomenon is ubiquitous in nature. Its prominent examples include swarms of fish, flight of birds in specific formations, and collective locomotion of small-scale biological objects, such as sperms. Such configurations help the members significantly reduce the energetic cost of propulsion as well as enhance their thrust and efficiency. In these natural dynamical systems, highly unsteady three-dimensional vortices emerge due to undulatory kinematics of each member of the school. It becomes more complex due to the interaction of coherent structures with the bodies moving in their vicinity. Furthermore, these activities generate pressure disturbances in the surrounding fluid, causing the spread of acoustic signals in water. This preamble provides the foundation of my plan to build and grow my research career in the fields of computational fluid-structure-acoustic interaction (FSAI) and bio-inspired robotics, which supports my long-term research objective of developing next-generation high-speed, efficient, and stealth nature-inspired robots. The presently proposed research focusses on the development of a novel computational solver through the sharp-interface immersed-boundary method to handle intense fluid-structure interactions, involving multiple oscillating bodies. Moreover, this solver facilitates the extraction and analysis of coherent flow structures to identify their roles for producing unsteady forces. The methodology will substantially contribute towards developing accurate theoretical and computational models of different natural swimmers and their schooling configurations. It is also particularly relevant to understand the mechanisms adopted by fish to communicate through pressure signals in surrounding flows, which allows them to feel the presence of other moving objects and acts as a tool for navigation. For this purpose, I will develop modules to compute acoustic signatures in the numerical solver to understand how vortex-body interactions impact the emission of pressure disturbances in flow fields.  This work is important to establish principles for designing autonomous fish-like robots capable of swimming silently without causing disruptions in natural habitats. Besides bio-inspired robots and energy harvesters, applications of the fundamental knowledge gained through this research and novel computational tools developed in this program are cross-disciplinary. These include the examination of various FSAI-related biological mechanisms, dynamics of different bodies in environmental flows, and the acoustic emissions in the environment from engineered systems. Along with training HQPs in multidisciplinary areas, this project will also address the development of educational modules on fluid dynamics for students in high school physics and introduce various outreach activities for young women and indigenous people to inspire them about STEM.