Influence of three dimensionality on propulsive flapping
Influence of three dimensionality on propulsive flapping
Propulsive flapping foils are widely studied in the development of swimming and flying animal-like autonomous systems. Numerical studies in this topic are mainly two-dimensional (2-D) studies, as they are quicker and cheaper, but this inhibits the three-dimensional (3-D) evolution of the shed vortices from leading and trailing edges. In this work, we examine the similarities and differences between 2-D and 3-D simulations through a case study in order to evaluate the efficacy and limitations of using 2-D simulations to describe a 3-D system. We simulate an infinite-span NACA0016 foil in both two and three dimensions at a Reynolds number of 5300 and an angle of attack of 10
°. The foil is subject to prescribed heaving and pitching kinematics with varying trailing-edge deflection amplitude. Our primary finding is that the flow and forces are effectively 2-D at intermediate amplitude-based Strouhal numbers (, where is the free-stream velocity and is the flapping frequency), for heaving, for pitching and for coupled motion, while 3-D effects dominate outside of these ranges. These 2-D regions begin when the fluid energy induced by the flapping motion overcomes the 3-D vortex shedding found on a stationary foil, and the flow reverts back to 3-D when the strength of the shed vortices overwhelms the stabilising influence of viscous dissipation. These results indicate that 3-D to 2-D transitions or vice versa are a balance between the strength and stability of leading/trailing-edge vortices and the flapping energy. However, 2-D simulations can still be used for flapping flight/swimming studies provided that the flapping amplitude/frequency is within a given range.
Swimming/flying, Vortex streets
A25-1-A25-14
Nasution, Andhini
b9e5a90e-08c3-4922-8307-26c420e854d8
Ganapathisubramani, Bharathram
5e69099f-2f39-4fdd-8a85-3ac906827052
Weymouth, Gabriel
b0c85fda-dfed-44da-8cc4-9e0cc88e2ca0
10 March 2020
Nasution, Andhini
b9e5a90e-08c3-4922-8307-26c420e854d8
Ganapathisubramani, Bharathram
5e69099f-2f39-4fdd-8a85-3ac906827052
Weymouth, Gabriel
b0c85fda-dfed-44da-8cc4-9e0cc88e2ca0
Nasution, Andhini, Ganapathisubramani, Bharathram and Weymouth, Gabriel
(2020)
Influence of three dimensionality on propulsive flapping.
Journal of Fluid Mechanics, 886, , [A25].
(doi:10.1017/jfm.2019.1078).
Abstract
Propulsive flapping foils are widely studied in the development of swimming and flying animal-like autonomous systems. Numerical studies in this topic are mainly two-dimensional (2-D) studies, as they are quicker and cheaper, but this inhibits the three-dimensional (3-D) evolution of the shed vortices from leading and trailing edges. In this work, we examine the similarities and differences between 2-D and 3-D simulations through a case study in order to evaluate the efficacy and limitations of using 2-D simulations to describe a 3-D system. We simulate an infinite-span NACA0016 foil in both two and three dimensions at a Reynolds number of 5300 and an angle of attack of 10
°. The foil is subject to prescribed heaving and pitching kinematics with varying trailing-edge deflection amplitude. Our primary finding is that the flow and forces are effectively 2-D at intermediate amplitude-based Strouhal numbers (, where is the free-stream velocity and is the flapping frequency), for heaving, for pitching and for coupled motion, while 3-D effects dominate outside of these ranges. These 2-D regions begin when the fluid energy induced by the flapping motion overcomes the 3-D vortex shedding found on a stationary foil, and the flow reverts back to 3-D when the strength of the shed vortices overwhelms the stabilising influence of viscous dissipation. These results indicate that 3-D to 2-D transitions or vice versa are a balance between the strength and stability of leading/trailing-edge vortices and the flapping energy. However, 2-D simulations can still be used for flapping flight/swimming studies provided that the flapping amplitude/frequency is within a given range.
Text
JFM Influence of Three Dimensionality on Propulsive Flapping_revision
- Accepted Manuscript
More information
Accepted/In Press date: 13 December 2019
e-pub ahead of print date: 15 January 2020
Published date: 10 March 2020
Additional Information:
Funding Information:
We would like to thank the Indonesia Endowment Fund for Education (LPDP), the IRIDIS High Performance Computing Facility with its associated support services at the University of Southampton, the Office of Naval Research Global Award N62909-18-1-2091 and Dr K. Hendrickson at MIT for the completion of this work.
Publisher Copyright:
© 2020 The Author(s). Published by Cambridge University Press.
Keywords:
Swimming/flying, Vortex streets
Identifiers
Local EPrints ID: 436680
URI: http://eprints.soton.ac.uk/id/eprint/436680
ISSN: 0022-1120
PURE UUID: f3ab5380-f845-4f65-9d87-ea460f82410f
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Date deposited: 20 Dec 2019 18:29
Last modified: 14 Dec 2024 05:02
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Author:
Andhini Nasution
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