The present study is on periodic three-dimensional biological flow during batlike flapping as well as fishlike undulation based spanwise symmetric three-dimensional (3D) kinematics and propulsion of batoid fish. For a single parameter based unified study on various types of real and hypothetical batoid fish, a 3D unified-kinematics model is proposed here. Using our immersed interface method based in-house code, the present numerical study is on the effect of various wavelengths (of the wavy undulation of a hydrofoil-shaped lateral cross section) and aspect ratios (of the elliptical span of the body)—corresponding to various types of batoid fishlike locomotion—at a constant nondimensional frequency of 0.5. Furthermore, for Dasyatis and a hypothetical batoid fish, the effect of various nondimensional frequencies is studied at an aspect ratio of 1. The study is done at a maximum nondimensional amplitude of 0.15 of the pitching/undulation and a Reynolds number of 10 000. A 3D vortex structure demonstrates a spanwise symmetric double row of vortex structure at the various wavelengths while a larger wavelength also results in a horseshoe type of vortices with multiple vortex rings. For propulsive performance, the maximum thrust force (propulsive efficiency) is obtained at an intermediate (smaller) wavelength. Further, with increasing aspect ratio, an increase in the thrust force and the propulsive efficiency are found for various wavelengths. A single-row (double-row) vortex structure leading to smaller (larger) thrust force is obtained at a smaller (larger) nondimensional frequency. Using the more realistic 3D kinematics, as compared to the 2D kinematics used earlier, more realistic flow structures and the associated propulsive performance parameters are presented that can be used for the efficient design of underwater vehicles.

中文翻译：

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各种类蝙蝠鱼运动的三维生物流体动力学研究

目前的研究是关于蝙蝠状拍打期间周期性的三维生物流以及基于类鱼的波浪状对称三维（3D）运动学和蝙蝠类鱼类的推进。为了对各种类型的真实和假设的蝙蝠鱼进行基于单参数的统一研究，在此提出了3D统一运动学模型。使用我们内部代码的沉浸式界面方法，当前的数值研究是针对各种波长（水翼形横截面的波浪状起伏）和长宽比（主体的椭圆跨度）的影响。在各种恒定的无量纲频率为0.5的情况下适应各种类蝙蝠鱼的运动。此外，对于达斯亚提斯和假想的蝙蝠鱼，以纵横比1来研究各种无量纲频率的影响。研究是在最大无量纲振幅为0.15的俯仰/起伏和雷诺数为10000的情况下进行的。3D涡旋结构证明了在不同的波长下，翼展方向对称的双排涡结构，而更大的波长也会导致具有多个涡环的马蹄型涡。对于推进性能，在中等（较小）波长处可获得最大推力（推进效率）。此外，随着纵横比的增加，发现对于各种波长推力和推进效率都增加。在较小（较大）的无量纲频率下可获得导致较小（较大）推力的单排（双排）涡流结构。与较早使用的2D运动学相比，使用更逼真的3D运动学，可以呈现出更逼真的流动结构和相关的推进性能参数，这些参数可用于水下车辆的高效设计。