Undulatory underwater swimming: linking vortex dynamics, thrust and wake structure with a biorobotic fish

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Bibliografiske detaljer
Udgivet i:Journal of Fluid Mechanics vol. 1015 (Jul 2025)
Hovedforfatter: Brouzet, Christophe
Andre forfattere: Raufaste, Christophe, Argentina, Médéric
Udgivet:
Cambridge University Press
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022 |a 0022-1120 
022 |a 1469-7645 
024 7 |a 10.1017/jfm.2025.10392  |2 doi 
035 |a 3232244642 
045 2 |b d20250701  |b d20250731 
084 |a 79037  |2 nlm 
100 1 |a Brouzet, Christophe  |u Université Côte d’Azur, CNRS, INPHYNI, Nice, France 
245 1 |a Undulatory underwater swimming: linking vortex dynamics, thrust and wake structure with a biorobotic fish 
260 |b Cambridge University Press  |c Jul 2025 
513 |a Journal Article 
520 3 |a Flapping-based propulsive systems rely on fluid–structure interactions to produce thrust. At intermediate and high Reynolds numbers, vortex formation and organisation in the wake of such systems are crucial for the generation of a propulsive force. In this work, we experimentally investigate the wake produced by a tethered robotic fish immersed in a water tunnel. By systematically varying the amplitude and frequency of the fish tail as well as the free stream speed, we are able to observe and characterise different vortex streets as a function of the Strouhal number. The produced wakes are three-dimensional and exhibit a classical V-shape, mainly with two oblique trains of vortex rings convecting outward. Using two-dimensional particle image velocimetry in the mid-span plane behind the fish and through extensive data processing of the velocity and vorticity fields, we demonstrate the strong couplings at place between vortex dynamics, thrust production and wake structure. The main results are twofold. First, by accounting for the obliqueness of the vortex trains, we quantify in experiments the evolution of vortex velocity components in both streamwise and transverse directions. We also measure key geometrical and dynamical properties such as wake angle, vortex ring orientation, diameter and vorticity. Remarkably, all of these quantities collapse onto master curves that also encompass data from previous studies. Second, we develop a quasi-two-dimensional model that incorporates both components of the momentum balance equation and introduces an effective spanwise thickness of the wake structure. This additional dimension, which scales with the physical thickness of the fish, captures the fine features of the three-dimensional wake. The model successfully explains the experimental master curves and highlights the links between vortex dynamics, thrust and wake geometry. Together, this framework offers a comprehensive understanding of the influence of the Strouhal number, providing universal insights relevant for both biological locomotion and bio-inspired propulsion systems. 
653 |a Flapping 
653 |a Data processing 
653 |a Fish 
653 |a High Reynolds number 
653 |a Vortices 
653 |a Particle image velocimetry 
653 |a Vorticity 
653 |a Swimming 
653 |a Vortex streets 
653 |a Thrust 
653 |a Locomotion 
653 |a Connectors 
653 |a Data analysis 
653 |a Wakes 
653 |a Propulsion systems 
653 |a Two dimensional models 
653 |a Vortex rings 
653 |a Simulation 
653 |a Velocity 
653 |a Curves 
653 |a Obliqueness 
653 |a Fluid-structure interaction 
653 |a Shape 
653 |a Strouhal number 
653 |a Reynolds number 
653 |a Couplings 
653 |a Thickness 
653 |a Environmental 
700 1 |a Raufaste, Christophe  |u Université Côte d’Azur, CNRS, INPHYNI, Nice, France; Institut Universitaire de France (IUF), Paris, France 
700 1 |a Argentina, Médéric  |u Université Côte d’Azur, CNRS, INPHYNI, Nice, France 
773 0 |t Journal of Fluid Mechanics  |g vol. 1015 (Jul 2025) 
786 0 |d ProQuest  |t Science Database 
856 4 1 |3 Citation/Abstract  |u https://www.proquest.com/docview/3232244642/abstract/embedded/L8HZQI7Z43R0LA5T?source=fedsrch