Tuna, known for high endurance cruising, have already inspired several underwater robots and swimming studies. This study uses a biomimetic robotic tuna to investigate how different caudal fin planform geometries affect the thrust production and flow structures during Body and/or Caudal Fin (BCF) swimming. The robot was tethered to a circulating water tunnel, and swimming was simulated by moving water at a constant speed relative to the stationary robot. Three differently shaped caudal fins were tested, one rectangular, one elliptical, and one swept. Area, aspect ratio, and rigidity were kept constant between the three fins to ensure that the effect of caudal fin shape could be isolated. The fins were tested at three freestream velocities and four Strouhal numbers (St) so that comparisons between the fins could be made for a variety of swimming scenarios. The swept fin, which is the tested caudal fin most similar to one found on a fusiform swimmer, had the greatest thrust potential at high St, followed by the elliptical fin. The rectangular fin generally produced the least thrust. It was shown that in addition to producing the most thrust, the swept fin also best stabilized the leading edge vortex that developed during the second half of the stroke.

中文翻译：

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尾鳍形状对三角帆形游泳运动员推力产生的影响

以高耐力巡航闻名的金枪鱼已经启发了一些水下机器人和游泳研究。这项研究使用仿生机器人金枪鱼研究了在身体和/或尾鳍（BCF）游泳过程中不同的尾鳍平面形状如何影响推力产生和流动结构。将机器人拴在循环水隧道上，并通过相对于固定机器人以恒定速度移动水来模拟游泳。测试了三个不同形状的尾鳍，一个为矩形，一个为椭圆形，另一为后掠。三个鳍片之间的面积，长宽比和刚度保持恒定，以确保可以隔离尾鳍形状的影响。鳍片在三个自由流速度和四个Strouhal数下（St），以便可以针对各种游泳场景进行脚蹼之间的比较。尾鳍是被测试的尾鳍，与梭形游泳者中的鳍最相似，在高St处具有最大推力，其次是椭圆形鳍。矩形鳍通常产生最小的推力。结果表明，除了产生最大的推力外，后掠鳍还可以最大程度地稳定冲程后半段形成的前缘涡流。