Why do anguilliform swimmers perform undulation with wavelengths shorter than their bodylengths?

Understanding the connection between physiology and kinematics of natural swimmers is of great importance to design efficient bio-inspired underwater vehicles. This study looks at high-fidelity three-dimensional numerical simulations for flows over an undulating American eel with prescribed anguilli...

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Bibliographic Details
Published in:Physics of fluids (1994) 2021-03, Vol.33 (3)
Main Authors: Khalid, Muhammad Saif Ullah, Akhtar, Imran, Hemmati, Arman
Format: Article
Language:English
Subjects:
Aquatic animals
Biomimetics
Fluid dynamics
Kinematics
Physics
Swimming
Three dimensional flow
Topology
Underwater vehicles
Wavelengths
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Summary:Understanding the connection between physiology and kinematics of natural swimmers is of great importance to design efficient bio-inspired underwater vehicles. This study looks at high-fidelity three-dimensional numerical simulations for flows over an undulating American eel with prescribed anguilliform kinematics. Particularly, our work focuses on why natural anguilliform swimmers employ wavelengths shorter than their bodylengths while performing wavy kinematics. For this purpose, we vary the undulatory wavelength for a range of values generally observed in different aquatic animals at Strouhal numbers 0.30 and 0.40. We observe that our anguilliform swimmer is able to demonstrate more suitable hydrodynamic performance for wavelengths of 0.65 and 0.80. For longer wavelengths, the swimmer experiences large frictional drag, which deteriorates its performance. The wake topology was dominated by hairpin-like structures, which are closely linked with the underlying physics of anguilliform swimming found in nature.
ISSN:1070-6631
1089-7666
DOI:10.1063/5.0040473