Huang Zihao, Wang Junshi, Dong Haibo
Department of Mechanical and Aerospace Engineering, University of Virginia, Charlottesville, VA 22903, United States of America.
Department of Mechanical and Aerospace Engineering, Princeton University, Princeton, NJ 08540, United States of America.
Bioinspir Biomim. 2025 Jul 21;20(4). doi: 10.1088/1748-3190/adebce.
Fish across many species share similar schooling behavior in which abundance flow interactions occur with hydrodynamic advantages from the vortex flow shed by the conspecifics. This study investigates the mechanisms of schooling interactions in thunniform swimmers, focusing on body effects, using high-fidelity three-dimensional direct numerical simulations of a pair of closely swimming tuna-like models with realistic body morphology and swimming kinematics. An in-house immerse-boundary-method-based incompressible Navier-Stokes flow solver is employed to resolve near-body vortex topology, and the results are analyzed in detail. The interaction mechanism is evaluated by varying the streamwise distance in the stagger formation from 0 to 1 body length (BL) in increments of 0.1 BL, and by introducing tailbeat phase differences at the optimal streamwise spacing, ranging from 0to 360in 45increments. Results identify an optimal streamwise distance of 0.5 BL, where the following fish achieve enhanced forward force production and propulsive efficiency. Notably, the following fish benefits from improved performance across all tailbeat phase differences, as the wake-fin interaction remains robust for its thrust enhancement. Flow analysis reveals that the vortex interception contributes to a 16% thrust improvement on the in-phase follower, while its drag reduction results from a combination of constructive pressure field interactions generating strong anterior suction and wake-body interactions producing forward force on the posterior body. These effects are amplified by tailbeat phase differences, with a 270phase difference yielding a 19% drag reduction on the following fish and 180enabling constant drag reduction throughout the motion cycle. This study highlights the enhanced swimming performance of closely paired tuna-like swimmers and identifies interaction mechanisms, offering valuable insights into the hydrodynamics of fish schooling and potential applications in underwater robotics.
许多物种的鱼类都具有相似的集群行为，在这种行为中，鱼群数量与水流相互作用，同物种个体产生的涡流带来水动力优势。本研究利用一对具有逼真身体形态和游泳运动学的类似金枪鱼模型进行高保真三维直接数值模拟，研究了梭形游泳者的集群相互作用机制，重点关注身体效应。采用基于浸入边界法的内部不可压缩纳维 - 斯托克斯流求解器来解析近体涡旋拓扑结构，并对结果进行详细分析。通过将交错编队中的流向距离从0变化到1个体长（BL），以0.1 BL为增量，并在最佳流向间距处引入尾摆相位差，相位差范围从0到360度，以45度为增量，来评估相互作用机制。结果确定了最佳流向距离为0.5 BL，在此距离下，跟随的鱼能够提高向前力的产生和推进效率。值得注意的是，在所有尾摆相位差下，跟随的鱼都能从性能提升中受益，因为尾流 - 鳍相互作用对其推力增强仍然很强劲。流动分析表明，涡旋拦截使同相位跟随者的推力提高了16%，而其阻力减小是由于建设性压力场相互作用产生强大的前部吸力以及尾流 - 身体相互作用在身体后部产生向前力的综合作用。这些效应通过尾摆相位差得到放大，270度的相位差使跟随的鱼的阻力降低了19%，180度的相位差使整个运动周期内的阻力持续降低。本研究突出了紧密配对的类似金枪鱼游泳者增强的游泳性能，并确定了相互作用机制，为鱼类集群的流体动力学以及水下机器人技术的潜在应用提供了有价值的见解。
