Numerical investigation of passive and active flapping in fish propulsion

近年来，随着工程师和生物学家对水生生物在设计和运动性能方面的显著多样性的关注，游泳流体动力学的研究引起了相当大的关注。研究的一个重要难点是如何使活鱼获得比现代机器鱼更高的推进效率和稳定性。这种困难阻碍了后者在实际应用中的实现。通过对鱼类在高速水流中的游动和薄结构被动拍动的观察，我们提出了对被动拍动和主动拍动的基本认识，从而最终实现高效的人工鲤鱼类游动器。本文的研究是基于流固耦合的双向耦合和三维数值模拟。我们申请两个资助期，共6年。在3年的第一个资助期内，重点将是模型开发和大涡模拟，重点是大流量结构和被动和主动扑动的重要贡献及其相互作用，以提高推进效率。在第二个资助期内，我们将专注于直接数值模拟和与游泳稳定性相关的主动控制。此外，如时间许可，我们会在第二个资助期内优化主动控制参数，以达致最高的推进效率和泳动稳定性。这些控制参数可用于指导高效机器鱼的设计。

The study of swimming hydrodynamics has attracted considerable attention in recent years as engineers and biologists have focused on the remarkable diversity in design and locomotion performance of aquatic organisms. One important difficulty of such study is that how the live fishes achieve much higher propulsion efficiency and stability than that of the up-to-date robotic fishes. Such difficulty hinders the realization of the latter for practical applications. Based on the observations on fish swimming and passive flapping of thin structure in high speed flow, we propose to develop a fundamental understanding of the passive and active flapping, which leads to the eventual realization of high effective artificial carangiform swimmer. The research is based on two-way coupling of flow-structure interaction, and three-dimensional numerical simulations. We apply for two funding periods for 6 years in toal. During the first funding period of 3 years the emphasis will be model development and large eddy simulation, which focuses on the large flow structures and the essential contributions of passive and active flapping and their interplay for increasing propulsion efficiency. In the second funding period we will focus on direct numerical simulations and the active controls relevant to swimming stability. Furthermore, if time permits, we will perform in the second funding period the optimization of the active control parameters to achieve the maximum propulsion efficiency and swimming stability. Such control parameters can be used to direct the design of high effective robotic fish.