Hydrodynamics study of dolphin's self-yaw motion realized by spanwise flexibility of caudal fin

Xia, Dan; Cao, Jinwei; Chen, Weishan; Wang, Xingsong

doi:10.1016/j.joes.2021.07.011

Cited by 11 publications

(2 citation statements)

References 38 publications

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“…As shown in Figure 16 b, the oxy section can only express the vorticity generated by the BCF module, including two diffuse vortex streets. This conclusion is consistent with the previous wake vortex structure reported in the single BCF propulsion [ 45 , 46 ]. Since the swing of the caudal fin is fixed and the basic frequency is unchanging, the value of frequency ratio β does not affect the overall layout of the vortex street generated by the caudal fin.…”

Section: Resultssupporting

confidence: 93%

A Comparative and Collaborative Study of the Hydrodynamics of Two Swimming Modes Applicable to Dolphins

2023

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This paper presents a hydrodynamics study that examines the comparison and collaboration of two swimming modes relevant to the universality of dolphins. This study utilizes a three-dimensional virtual swimmer model resembling a dolphin, which comprises a body and/or caudal fin (BCF) module, as well as a medium and/or paired fin (MPF) module, each equipped with predetermined kinematics. The manipulation of the dolphin to simulate various swimming modes is achieved through the application of overlapping grids in conjunction with the parallel hole cutting technique. The findings demonstrate that the swimming velocity and thrust attained through the single BCF mode consistently surpass those achieved through the single MPF mode and collaborative mode. Interestingly, the involvement of the MPF mode does not necessarily contribute to performance enhancement. Nevertheless, it is encouraging to note that adjusting the phase difference between the two modes can partially mitigate the limitations associated with the MPF mode. To further investigate the potential advantages of dual-mode collaboration, we conducted experiments by increasing the MPF frequency while keeping the BCF frequency constant, thus introducing the concept of frequency ratio (β). In comparison to the single BCF mode, the collaborative mode with a high β exhibits superior swimming velocity and thrust. Although its efficiency experiences a slight decrease, it tends to stabilize. The corresponding flow structure indirectly verifies the favorable impact of collaboration.

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Section: Resultssupporting

confidence: 93%

A Comparative and Collaborative Study of the Hydrodynamics of Two Swimming Modes Applicable to Dolphins

2023

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“…In Figure 2B, the surface of the dolphin is discretized into a uniform triangular grid. In a large number of previous studies [25,26], we used this meshing method to simulate the flexible swing of various fins to achieve underwater swimming. For the boundary conditions of inflow and outflow, we set zero velocity and pressure gradient for both the inlet and outlet boundary.…”

Section: Computational Models and Gridsmentioning

confidence: 99%

Hydrodynamics of Butterfly-Mode Flapping Propulsion of Dolphin Pectoral Fins with Elliptical Trajectories

Xia,

Li,

Lei

et al. 2023

Biomimetics

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This article aims to numerically study the hydrodynamic performance of the bionic dolphin equipped with a pair of rigid pectoral fins. We use dynamic-grid technology and user-defined functions to simulate a novel butterfly-mode flapping propulsion of the fins. This pattern of propulsion is composed of three angular degrees of freedom including the pitch angle ϕp, the azimuth angle ϕa and the roll angle ϕr, which can be divided into four stages for analysis within a single cycle. The stroke of one single pectoral fin can be approximated as an ellipse trajectory, where the amplitudes of ϕa and ϕp, respectively, determine the major and minor axes of the ellipse. The fluid dynamics involved in the specific butterfly pattern is mathematically formulated, and numerical simulation is conducted to investigate the propulsion quantitatively. The results show that the dolphin with a higher water striking frequency f can acquire higher propulsion speed and efficiency. Furthermore, the shape of the ellipse trajectory under different conditions could also have different propulsion effects. The periodic generation and disappearance of vortex structures in the butterfly flapping mode show the evolution process of fluid flow around a pair of pectoral fins, which reveals the influence of motion parameters on fluid dynamics under different working conditions.

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Diving dynamics identification and motion prediction for marine crafts using field data

Zhong,

Yu,

Bai

et al. 2024

Journal of Ocean Engineering and Science

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Hydrodynamics study of dolphin's self-yaw motion realized by spanwise flexibility of caudal fin

Cited by 11 publications

References 38 publications

A Comparative and Collaborative Study of the Hydrodynamics of Two Swimming Modes Applicable to Dolphins

A Comparative and Collaborative Study of the Hydrodynamics of Two Swimming Modes Applicable to Dolphins

Hydrodynamics of Butterfly-Mode Flapping Propulsion of Dolphin Pectoral Fins with Elliptical Trajectories

Diving dynamics identification and motion prediction for marine crafts using field data

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