Department of Ocean and Mechanical Engineering, Florida Atlantic University, Boca Raton, FL, United States of America.
Bioinspir Biomim. 2022 May 13;17(4). doi: 10.1088/1748-3190/ac6375.
Several fishes swim by undulating a thin and elongated median fin while the body is mostly kept straight, allowing them to perform forward and directional maneuvers. We used a robotic vessel with similar fin propulsion to determine the thrust scaling and efficiency. Using precise force and swimming kinematics measurements with the robotic vessel, the thrust generated by the undulating fin was found to scale with the square of the relative velocity between the free streaming flow and the wave speed. A hydrodynamic efficiency is presented based on propulsive force measurements and modelling of the power required to oscillate the fin laterally. It was found that the propulsive efficiency has a broadly high performance versus swimming speed, with a maximum efficiency of 75%. An expression to calculate the swimming speed over wave speed was found to depend on two parameters:/(ratio between body frontal area to fin swept area) and/(ratio of body drag to fin thrust coefficient). The models used to calculate propulsive force and free-swimming speed were compared with experimental results. The broader impacts of these results are discussed in relation to morphology and the function of undulating fin swimmers. In particular, we suggest that the ratio of fin and body height found in natural swimmers could be due to a trade-off between swimming efficiency and swimming speed.
几条鱼在身体基本保持直线的情况下，通过波动一个细长的中间鳍来游动，从而能够进行前进和定向的机动动作。我们使用具有类似鳍推进的机器人船来确定推力缩放和效率。使用机器人船的精确力和游泳运动学测量，发现波动鳍产生的推力与自由流速度和波速之间的相对速度的平方成正比。基于推进力测量和横向振荡鳍所需功率的建模，提出了一种水动力效率。发现推进效率具有广泛的高速度性能，最大效率为 75%。发现计算波速上游泳速度的表达式取决于两个参数：/(体前面积与鳍扫掠面积之比)和/(体阻力与鳍推力系数之比)。用于计算推进力和自由游泳速度的模型与实验结果进行了比较。讨论了这些结果在形态和波动鳍游泳者功能方面的更广泛影响。特别是，我们建议在自然游泳者中发现的鳍和身体高度的比例可能是由于游泳效率和游泳速度之间的权衡。
