螺旋千斤顶运动的模态分解及流体与尾鳍的相互作用
Modal Decompositions of the Kinematics of Crevalle Jack and the Fluid-Caudal Fin Interaction
摘要：
由于自然水生物种的柔性身体与周围的水之间的强烈相互作用，了解生物启发游泳的管理机制一直具有挑战性。在本文中，我们采用先进的模态分解技术，适当的正交分解和动态模式分解，提取能量最强的时空正交分量的复杂运动学的Crevalle杰克（Caranx河马）鱼。然后，我们提出了一个计算框架处理流体-结构相互作用相关的问题，以调查他们对高度非线性系统的整体动力学的贡献。我们发现，这种鱼的起伏运动可以描述只有两个驻波一样的空间正交模式。构建的数据集，从我们的数值模拟流膜尾鳍的杰克鱼，我们的模态分析表明，只有前几个模式接收能量从流体和结构，但流体的贡献在较高的模式是最小的。对于这里考虑的粘性和过渡流条件，空间和时间正交模式显示出惊人的相似的相干流结构。我们的研究有望帮助开发数据驱动的降维数学模型，以研究生物启发的游泳机器人的动力学，并开发新的有效的控制策略，使其性能更接近真实的鱼类。
英文摘要：
To understand the governing mechanisms of bio-inspired swimming has always been challenging due to intense interactions between the flexible bodies of natural aquatic species and water around them. In this paper, we employ advanced modal decomposition techniques; proper orthogonal decomposition and dynamic mode decomposition, to extract energetically strongest spatio-temporal orthonormal components of complex kinematics of a Crevalle Jack (Caranx hippos) fish. Then, we present a computational framework for handling fluid-structure interaction related problems in order to investigate their contributions towards the overall dynamics of highly nonlinear systems. We find that the undulating motion of this fish can be described by only two standing-wave like spatially orthonormal modes. Constructing the data set from our numerical simulations for flows over the membranous caudal fin of the Jack fish, our modal analyses reveal that only the first few modes receive energy from both the fluid and structure, but the contribution of fluid in the higher modes is minimal. For the viscous and transitional flow conditions considered here, both spatially and temporally orthonormal modes show strikingly similar coherent flow structures. Our investigations are expected to assist in developing data-driven reduced-dimensional mathematical models to examine the dynamics of bio-inspired swimming robots and develop new and effective control strategies to bring their performance closer to real fish species.
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