Thrust-efficiency limits of a swimming tail with variable chordwise flexural rigidity

Abstract Emulating oscillations performed by natural swimmers can provide different functionalities than those of propeller-based underwater robots. Yet, to successfully accomplish specific missions under limited power, there is a need to design efficient bio-inspired robots. Adding an appropriate l...

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Main Authors: Hossam Alqaleiby, Muhammad R. Hajj
Format: Article
Language:English
Published: Nature Portfolio 2025-02-01
Series:Scientific Reports
Subjects:
Online Access:https://doi.org/10.1038/s41598-025-88365-x
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author Hossam Alqaleiby
Muhammad R. Hajj
author_facet Hossam Alqaleiby
Muhammad R. Hajj
author_sort Hossam Alqaleiby
collection DOAJ
description Abstract Emulating oscillations performed by natural swimmers can provide different functionalities than those of propeller-based underwater robots. Yet, to successfully accomplish specific missions under limited power, there is a need to design efficient bio-inspired robots. Adding an appropriate level of flexibility to flapping caudal fins (tails) of robots emulating the thunniform swimming mode has been shown to enhance the thrust generation over a finite range of the flapping frequency. Still, in many cases, adding flexibility to increase thrust generation may require increased input power, which may cause a significant reduction in the efficiency. These observations lead to the concept of enhanced performance by varying the stiffness of the tail as in the case of natural swimmers. This study is concerned with assessing the impact of varying the chordwise stiffness on the tail deflection and flow dynamics, including contributions of added mass and circulation forces to thrust generation and their impact on efficiency. The simulation data are used to identify specific flow dynamics and tail deflections associated with the enhanced thrust generation and/or efficiency, and to define a performance limit expressed as the maximum efficiency as a function of the thrust coefficient.
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spelling doaj-art-aa7c60e9306a4386a103976162e61e522025-02-09T12:37:52ZengNature PortfolioScientific Reports2045-23222025-02-0115111310.1038/s41598-025-88365-xThrust-efficiency limits of a swimming tail with variable chordwise flexural rigidityHossam Alqaleiby0Muhammad R. Hajj1Davidson Laboratory, Department of Civil, Environmental and Ocean Engineering, Stevens Institute of TechnologyDavidson Laboratory, Department of Civil, Environmental and Ocean Engineering, Stevens Institute of TechnologyAbstract Emulating oscillations performed by natural swimmers can provide different functionalities than those of propeller-based underwater robots. Yet, to successfully accomplish specific missions under limited power, there is a need to design efficient bio-inspired robots. Adding an appropriate level of flexibility to flapping caudal fins (tails) of robots emulating the thunniform swimming mode has been shown to enhance the thrust generation over a finite range of the flapping frequency. Still, in many cases, adding flexibility to increase thrust generation may require increased input power, which may cause a significant reduction in the efficiency. These observations lead to the concept of enhanced performance by varying the stiffness of the tail as in the case of natural swimmers. This study is concerned with assessing the impact of varying the chordwise stiffness on the tail deflection and flow dynamics, including contributions of added mass and circulation forces to thrust generation and their impact on efficiency. The simulation data are used to identify specific flow dynamics and tail deflections associated with the enhanced thrust generation and/or efficiency, and to define a performance limit expressed as the maximum efficiency as a function of the thrust coefficient.https://doi.org/10.1038/s41598-025-88365-xFish locomotionChordwise stiffnessFinite-element methodStiffness profile3D unsteady vortex lattice method
spellingShingle Hossam Alqaleiby
Muhammad R. Hajj
Thrust-efficiency limits of a swimming tail with variable chordwise flexural rigidity
Scientific Reports
Fish locomotion
Chordwise stiffness
Finite-element method
Stiffness profile
3D unsteady vortex lattice method
title Thrust-efficiency limits of a swimming tail with variable chordwise flexural rigidity
title_full Thrust-efficiency limits of a swimming tail with variable chordwise flexural rigidity
title_fullStr Thrust-efficiency limits of a swimming tail with variable chordwise flexural rigidity
title_full_unstemmed Thrust-efficiency limits of a swimming tail with variable chordwise flexural rigidity
title_short Thrust-efficiency limits of a swimming tail with variable chordwise flexural rigidity
title_sort thrust efficiency limits of a swimming tail with variable chordwise flexural rigidity
topic Fish locomotion
Chordwise stiffness
Finite-element method
Stiffness profile
3D unsteady vortex lattice method
url https://doi.org/10.1038/s41598-025-88365-x
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AT muhammadrhajj thrustefficiencylimitsofaswimmingtailwithvariablechordwiseflexuralrigidity