This study explores the nature of forces developed by a batoid-inspired undulating circular planform. The forces that arise from this type of fin-based propulsion have two components, one due to added mass effects and a second one due to circulation. The present work studies the impact of specific fin kinematic parameters on the individual contributions of these components. Numerical simulations are performed on a deforming boundary fitted grid around an undulating circular planform. Flow physics and force generation are analyzed at Reynolds numbers up to 500. A detailed analysis is presented of the impact of wavenumber, amplitude of the fin traveling wave, and Strouhal number on propulsive forces using flow contours and pressure distributions on the planform. The sway coefficient increases with decrease in wavenumber, whereas the thrust coefficient reaches a maximum at a wavenumber of one. The yaw moment coefficient increases up to wavenumber of 1.5 and remains nearly constant after. For the cases studied, circulation has a larger impact compared to added mass effects in the overall force generation, and the role of edge vortices is explored in detail. The wake formed during half of the fin flapping cycle has two distinctive parts. One part is shed as an edge vortex toward the planform circumference and the other part is shed from the trailing edge of the planform, where both vortex structures are attached. These two vortices are of same sign. Over the next half-cycle a similar couple, but with opposite sign, is shed and inter-locks with the previous pair. The edge vortices on both sides of the planform are connected like a horse-shoe. The results enable a better understanding of the link between batoid-like undulatory fin kinematics and propulsive force generation and can help in the design and control of bio-inspired underwater vehicles.

中文翻译：

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batoid 激发的起伏运动对圆形平面推进力的影响

这项研究探索了受蝙蝠形启发的起伏圆形平面所产生的力的性质。这种基于鳍的推进产生的力有两个组成部分，一个是由于附加的质量效应，另一个是由于循环。目前的工作研究了特定鳍运动学参数对这些组件的单独贡献的影响。数值模拟是在围绕起伏圆形平面的变形边界拟合网格上进行的。在高达 500 的雷诺数下分析了流动物理和力的生成。使用流动轮廓和平面上的压力分布详细分析了波数、鳍行波幅度和 Strouhal 数对推进力的影响。摇摆系数随着波数的减少而增加，而推力系数在波数为 1 时达到最大值。偏航力矩系数增加到波数 1.5，之后几乎保持不变。对于所研究的案例，与整体力生成中的附加质量效应相比，循环具有更大的影响，并且详细探讨了边缘涡流的作用。在鳍摆动周期的一半期间形成的尾流有两个不同的部分。一部分作为边缘涡流向平面圆周脱落，另一部分从平面的后缘脱落，两个涡流结构都附着在此处。这两个漩涡同号。在接下来的半个周期中，一对类似但符号相反的配对会脱落并与前一对互锁。平面两侧的边缘涡流像马蹄铁一样相连。