Ocean and Mechanical Engineering, Florida Atlantic University, Boca Raton, FL 33431, United States of America.
Bioinspir Biomim. 2018 Jul 20;13(5):056006. doi: 10.1088/1748-3190/aacd26.
Undulatory fin propulsion exhibits a high degree of maneuver control-an ideal feature for underwater vessels exploring complex environments. In this work, we developed and tested a self-contained, free-swimming robot with a single undulating fin running along the length of the robot, which controls both forward motion and directional maneuvers. We successfully replicated several maneuvers including forward swimming, reversed motion, diving, station-keeping and vertical swimming. For each maneuver, a series of experiments was performed as a function of fin frequency, wavelength and traveling wave direction to measure swimming velocities, orientation angles and mean power consumption. In addition, 3D flow fields were measured during forward swimming and station-keeping using volumetric particle image velocimetry (PIV). The efficiency for forward swimming was compared using three metrics: cost of transport, wave efficiency and Strouhal number (St). The results indicate that the cost of transport exhibits a V-shape trend with the minimum value at low swimming velocity. The robot reaches optimal wave efficiency and locomotor performance at a range of 0.2-0.4 St. Volumetric PIV data reveal the shed of vortex tubes generated by the fin during forward swimming and station keeping. For forward swimming, a series of vortex tubes are shed off the fin edge with a lateral and downward direction with respect to the longitudinal axis of the fin. For station keeping, flow measurements suggest that the vortex tubes are shed at the mid-section of the fin while the posterior and anterior segment of the vortex stay attached to the fin. These results agree with the previous vortex structures based on simulations and 2D PIV. The development of this vessel with high maneuverability and station keeping performance has applications for oceanography, coastal exploration, defense, the oil industry and other marine industries where operations are unsafe or impractical for divers or human-piloted vessels.
波动鳍推进表现出高度的机动控制——这是探索复杂环境的水下航行器的理想特征。在这项工作中，我们开发并测试了一种自包含的、自由游动的机器人，它有一个单一的波动鳍沿着机器人的长度运行，控制着前进运动和方向机动。我们成功地复制了几种机动，包括前进游泳、反向运动、潜水、保持位置和垂直游泳。对于每种机动，我们都进行了一系列实验，作为鳍频率、波长和行波方向的函数，以测量游泳速度、方向角度和平均功率消耗。此外，使用体积粒子图像测速（PIV）在前进游泳和保持位置时测量了 3D 流场。使用三种度量标准比较了前进游泳的效率：运输成本、波效率和斯特劳哈尔数（St）。结果表明，运输成本呈 V 形趋势，在低游泳速度下达到最小值。机器人在 0.2-0.4St 的范围内达到最佳波效率和运动性能。体积 PIV 数据揭示了鳍在前进游泳和保持位置时产生的涡管的脱落。对于前进游泳，一系列涡管从鳍边缘以侧向和向下的方向相对于鳍的纵轴脱落。对于保持位置，流动测量表明，涡管在鳍的中部脱落，而涡的后段和前段仍附着在鳍上。这些结果与基于模拟和 2D PIV 的先前涡结构一致。这种具有高机动性和保持位置性能的船舶的发展在海洋学、沿海勘探、国防、石油工业和其他海洋工业中具有应用价值，在这些领域，潜水员或载人船只的操作是不安全或不切实际的。
