Abstract In the present paper, the assessment of the hydrodynamics of fish swimming wake-flow is carried out to identify the main features related to the propulsion performance. Two different fish models with caragiform kinematics are studied: tuna fish (Thunnus atlanticus) and lambari (Astyanax bimaculatus). CFD methods were used to simulate laminar and turbulent flow regimes and a dynamically adaptive mesh discretization (ALE) was employed to reproduce fish motion. Simulations were run in a typical range of Reynolds (Re) and Strouhal (St) numbers of the fish swimming flow investigating hydrodynamics forces and the flow patterns of the induced fish-swimming wake. Firstly, equilibrium condition (drag balancing thrust) for Strouhal was achieved for each Reynolds number and three-dimensional wake structures were evaluated concluding that fish swimming experiencing a forward locomotion movement with a reversal von-Karman vortex street and a high-velocity jet through the downstream direction. Finally, vorticity dynamics analysis showing that the leading-edge vortex produced by the caudal fin is associated to the peak of thrust in the motion cycle.

中文翻译：

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鱼类游泳中的三维粘性尾流 - CFD 研究

摘要 在本文中，进行了鱼类游泳尾流的流体动力学评估，以确定与推进性能相关的主要特征。研究了两种具有角形运动学的不同鱼类模型：金枪鱼 (Thunnus atlanticus) 和lambari (Astyanax bimaculatus)。CFD 方法用于模拟层流和湍流流态，并采用动态自适应网格离散化 (ALE) 来重现鱼的运动。模拟在鱼游流的典型雷诺数 (Re) 和 Strouhal (St) 数范围内运行，研究水动力和诱导的鱼类游动尾流的流动模式。首先，每个雷诺数都达到了 Strouhal 的平衡条件（阻力平衡推力），并评估了三维尾流结构，得出的结论是，鱼游泳时经历了向前运动，反向 von-Karman 涡街和通过下游方向的高速射流. 最后，涡度动力学分析表明尾鳍产生的前缘涡流与运动周期中的推力峰值有关。