Lighthill细长体理论相关的流动
Flow associated with Lighthill's elongated-body theory
AI总结：
本文重新审视Lighthill细长体理论，利用势流基本奇点提供现代解释，并扩展预测鱼类运动引起的完整三维流场，结果与数值模拟吻合。
摘要：
作用于波动游动鱼类的流体动力由两个分量组成：基于阻力的阻力力和源于附加水质量必要加速的反作用力。Lighthill的细长体理论基于势流，为计算这种反作用力提供了框架。通过利用大多数鱼类的高纵横比，该理论将问题简化为沿鱼体的一系列独立的二维流体切片，这些切片与鱼体和相邻切片交换动量。利用动量守恒论证，Lighthill的理论仅基于尾鳍的尺寸和运动学预测了波动鱼类产生的总推力。然而，独立切片的假设导致了常见的误解，即产生的流动缺乏纵向分量。在本文中，我们重新审视了Lighthill的理论，使用势流的基本奇点提供了现代重新解释。然后我们将其扩展以预测由鱼体运动引起的完整三维流场。我们的结果与真实鱼类几何形状的数值模拟相比具有良好的一致性。
英文摘要：
The hydrodynamic forces acting on an undulating swimming fish consist of two components: a drag-based resistive force and a reactive force originating from the necessary acceleration of an added mass of water. Lighthill's elongated-body theory, based on potential flow, provides a framework for calculating this reactive force. By leveraging the high aspect ratio of most fish, the theory simplifies the problem into a series of independent two-dimensional slices of fluids along the fish's body, which exchange momentum with the body and neighbouring slices. Using momentum conservation arguments, Lighthill's theory predicts the total thrust generated by an undulating fish, based solely on the dimensions and kinematics of its caudal fin. However, the assumption of independent slices has led to the common misconception that the flow produced lacks a longitudinal component. In this paper, we revisit Lighthill's theory, offering a modern reinterpretation using essential singularities of potential flows. We then extend it to predict the full three-dimensional flow field induced by the fish's body motion. Our results compare favourably with numerical simulations of realistic fish geometries.
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