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Added mass energy recovery of octopus-inspired shape change

Added mass energy recovery of octopus-inspired shape change
Added mass energy recovery of octopus-inspired shape change
Dynamic shape change of the octopus mantle during fast jet escape manoeuvres results in added mass energy recovery to the energetic advantage of the octopus, giving escape thrust and speed additional to that due to jetting alone. We show through numerical simulations and experimental validation of overall wake behaviour, that the success of the energy recovery is highly dependent on shrinking speed and Reynolds number, with secondary dependence on shape considerations and shrinking amplitude. The added mass energy recovery ratio ?ma, which measures momentum recovery in relation to the maximum momentum recovery possible in an ideal flow, increases with increasing the non-dimensional shrinking parameter ??=a?max/URe0????, where a?max is the maximum shrinking speed, U is the characteristic flow velocity and Re0???? is the Reynolds number at the beginning of the shrinking motion. An estimated threshold ???10 determines whether or not enough energy is recovered to the body to produce net thrust. Since there is a region of high transition for 10<??<30 where the recovery performance varies widely and for ??>100 added mass energy is recovered at diminishing returns, we propose a design criterion for shrinking bodies to be in the range of 50<??<100, resulting in 61–82 % energy recovery.
0022-1120
155-174
Steele, S.C.
366a881a-fcfb-42d5-bd18-bb26a5f45c70
Weymouth, G.D.
b0c85fda-dfed-44da-8cc4-9e0cc88e2ca0
Triantafyllou, M.S.
8b2b42be-39f5-41ab-b9c8-5ba019b04b6d
Steele, S.C.
366a881a-fcfb-42d5-bd18-bb26a5f45c70
Weymouth, G.D.
b0c85fda-dfed-44da-8cc4-9e0cc88e2ca0
Triantafyllou, M.S.
8b2b42be-39f5-41ab-b9c8-5ba019b04b6d

Steele, S.C., Weymouth, G.D. and Triantafyllou, M.S. (2017) Added mass energy recovery of octopus-inspired shape change. Journal of Fluid Mechanics, 810, 155-174. (doi:10.1017/jfm.2016.701).

Record type: Article

Abstract

Dynamic shape change of the octopus mantle during fast jet escape manoeuvres results in added mass energy recovery to the energetic advantage of the octopus, giving escape thrust and speed additional to that due to jetting alone. We show through numerical simulations and experimental validation of overall wake behaviour, that the success of the energy recovery is highly dependent on shrinking speed and Reynolds number, with secondary dependence on shape considerations and shrinking amplitude. The added mass energy recovery ratio ?ma, which measures momentum recovery in relation to the maximum momentum recovery possible in an ideal flow, increases with increasing the non-dimensional shrinking parameter ??=a?max/URe0????, where a?max is the maximum shrinking speed, U is the characteristic flow velocity and Re0???? is the Reynolds number at the beginning of the shrinking motion. An estimated threshold ???10 determines whether or not enough energy is recovered to the body to produce net thrust. Since there is a region of high transition for 10<??<30 where the recovery performance varies widely and for ??>100 added mass energy is recovered at diminishing returns, we propose a design criterion for shrinking bodies to be in the range of 50<??<100, resulting in 61–82 % energy recovery.

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Steele 2016c JFM shrinking.pdf - Accepted Manuscript
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Accepted/In Press date: 18 October 2016
e-pub ahead of print date: 24 November 2016
Published date: January 2017
Organisations: Fluid Structure Interactions Group

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Local EPrints ID: 404186
URI: http://eprints.soton.ac.uk/id/eprint/404186
ISSN: 0022-1120
PURE UUID: 989cadc4-fb41-4ddf-915f-cf74afaf3a0c
ORCID for G.D. Weymouth: ORCID iD orcid.org/0000-0001-5080-5016

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Date deposited: 03 Jan 2017 14:17
Last modified: 28 Apr 2022 05:39

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Contributors

Author: S.C. Steele
Author: G.D. Weymouth ORCID iD
Author: M.S. Triantafyllou

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