仿生自主推进中的被动柔性和多体相互作用研究

In this project, investigations of passive flexibility and many-body interaction in bio-inspired propulsion will be conducted by performing numerical simulations of simplified mathematical model. The proposed research belongs to an interdisciplinary field involving both biological/bio-inspired propulsion and computational fluid dynamics. The issues we set out to explore include: (1) How to mimic several commonly seen fish swimming modes on a locally actuated thin elastic filament/panel, by utilizing passive flexibility and fluid-structure interaction? (2) Whether the stable formations of several self-propelled "robotic fish" can spontaneously emerge? Whether swimming in school enjoys hydrodynamic advantage over swimming alone? Lighthill once conjectured that "the orderly patterns in fish schools may spontaneously arise as a consequence of passive flow-mediated interactions". This scientific hypothesis has never been thoroughly tested before. The proposed research aims at finding more supporting evidence for the Lighthill conjecture by studying the interactions among several self-propelled "robotic fish". The result of this work not only has important impact on the fundamental aspects of bio-fluid mechanics, but also provides a guide for design, optimization and formation control of bio-inspired underwater vehicles.

本项目通过简化数学模型的数值模拟，研究仿生推进中的被动柔性效应和多体干扰问题。研究课题属于生物/仿生推进与计算流体力学的交叉领域。研究内容包括：（1）如何在局部驱动的弹性细丝/薄板上，利用被动柔性和流固耦合模仿几类常见的鱼游方式实现推进？（2）多条自主推进的流固耦合“机器鱼”能否自发形成稳定的队形？集群式推进是否比个体推进更具有流体力学上的优势？Lighthill曾猜测“鱼群的有序排列方式可能完全因被动的流体力学相互作用而自发产生”。该猜想的合理性一直没有得到充分的检验。本项目将试图通过多条“机器鱼”的流动干扰研究，找到Lighthill猜想的更多支持性证据。研究结果不仅在生物流体力学的基础理论上具有重要意义，还可为仿生水下航行器的设计与优化以及航行器的编队控制提供指导。

本项目利用简化数学模型和数值模拟，研究生物在流体中的集群形成以及推进中的被动柔性效应。主要内容包括：鱼群的自发稳定队形问题（Lighthill猜想）；仿生水下航行器的间歇式推进；头部俯仰—升沉联合驱动的柔性板自主推进。. 应用数学家James Lighthill曾猜想鱼群的形成与维持可能借助了被动的流体力学相互作用。我们研究了由2至4个仿鱼式自主推进体组成的“仿生鱼群”。我们发现了14种自发形成的稳定队形，其中并列式队形的推进效率最高。我们的研究成果为“Lighthill猜想”提供了有力证据。此外，我们发现相同巡游速度的条件下，如果雷诺数足够高并且占空比中等，则间歇式推进的效率高于连续式推进。我们还发现在很大的刚度范围内，头部俯仰-升沉联合驱动的推进性能优于俯仰驱动。. 本项目的研究成果不仅在生物流体力学的基础理论上具有重要意义，还可为仿生水下航行器的设计与优化以及航行器的编队控制提供指导。