Hydromechanics of lunate-tail swimming propulsion. Part 2
This paper investigates the propulsive performance of the lunate tails of aquatic animals achieving high propulsive efficiency (the hydromechanical efficiency being defined as the ratio of the work done by the mean forward thrust to the mean rate at which work is done by the tail movements on the su...
Published in: | Journal of Fluid Mechanics |
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Language: | English |
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Cambridge University Press (CUP)
1977
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Online Access: | http://dx.doi.org/10.1017/s0022112077000032 https://www.cambridge.org/core/services/aop-cambridge-core/content/view/S0022112077000032 |
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crcambridgeupr:10.1017/s0022112077000032 2024-06-23T07:56:20+00:00 Hydromechanics of lunate-tail swimming propulsion. Part 2 Chopra, M. G. Kambe, T. 1977 http://dx.doi.org/10.1017/s0022112077000032 https://www.cambridge.org/core/services/aop-cambridge-core/content/view/S0022112077000032 en eng Cambridge University Press (CUP) https://www.cambridge.org/core/terms Journal of Fluid Mechanics volume 79, issue 1, page 49-69 ISSN 0022-1120 1469-7645 journal-article 1977 crcambridgeupr https://doi.org/10.1017/s0022112077000032 2024-06-12T04:03:51Z This paper investigates the propulsive performance of the lunate tails of aquatic animals achieving high propulsive efficiency (the hydromechanical efficiency being defined as the ratio of the work done by the mean forward thrust to the mean rate at which work is done by the tail movements on the surrounding fluid). Small amplitude heaving and pitching motions of a finite flat-plate wing of general planform with a rounded leading edge and a sharp trailing edge are considered. This is a generalization of Chopra's (1974) work on model rectangular tails. This motion characterizes vertical oscillations of the horizontal tail flukes of some cetacean mammals. The same oscillations, turned through a right angle to become horizontal motions of side-slip and yaw, characterize the caudal fins of certain fast-swimming fishes; viz. wahoo, tunny, wavyback skipjack, etc., from the Percomorphi and whale shark, porbeagle, etc., from the Selachii. Davies’ (1963, 1976) method of finding the loading distribution on the wing and generalized force coefficients, through approximate solution of an integral equation relating the loading and the upwash (lifting-surface theory), is used to find the total thrust and the rate of working of the tail, which in turn specify the hydromechanical swimming performance of the animals. The physical parameters concerned are the tail aspect ratio ((span) 2 /planform area), the reduced frequency (angular frequency x typical length/forward speed), the feathering parameter (the ratio of the tail slope to the slope of the path of the pitching axis), the position of the pitching axis, and the curved shapes of the leading and trailing edges. The variation of the thrust and the propulsive efficiency with these parameters has been discussed to indicate the optimum shape of the tail. It is found that, compared with a rectangular tail, a curved leading edge as in lunate tails gives a reduced thrust contribution from the leading-edge suction for the same total thrust; however, a sweep angle of the leading edge ... Article in Journal/Newspaper Porbeagle Cambridge University Press Journal of Fluid Mechanics 79 1 49 69 |
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Cambridge University Press |
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crcambridgeupr |
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English |
description |
This paper investigates the propulsive performance of the lunate tails of aquatic animals achieving high propulsive efficiency (the hydromechanical efficiency being defined as the ratio of the work done by the mean forward thrust to the mean rate at which work is done by the tail movements on the surrounding fluid). Small amplitude heaving and pitching motions of a finite flat-plate wing of general planform with a rounded leading edge and a sharp trailing edge are considered. This is a generalization of Chopra's (1974) work on model rectangular tails. This motion characterizes vertical oscillations of the horizontal tail flukes of some cetacean mammals. The same oscillations, turned through a right angle to become horizontal motions of side-slip and yaw, characterize the caudal fins of certain fast-swimming fishes; viz. wahoo, tunny, wavyback skipjack, etc., from the Percomorphi and whale shark, porbeagle, etc., from the Selachii. Davies’ (1963, 1976) method of finding the loading distribution on the wing and generalized force coefficients, through approximate solution of an integral equation relating the loading and the upwash (lifting-surface theory), is used to find the total thrust and the rate of working of the tail, which in turn specify the hydromechanical swimming performance of the animals. The physical parameters concerned are the tail aspect ratio ((span) 2 /planform area), the reduced frequency (angular frequency x typical length/forward speed), the feathering parameter (the ratio of the tail slope to the slope of the path of the pitching axis), the position of the pitching axis, and the curved shapes of the leading and trailing edges. The variation of the thrust and the propulsive efficiency with these parameters has been discussed to indicate the optimum shape of the tail. It is found that, compared with a rectangular tail, a curved leading edge as in lunate tails gives a reduced thrust contribution from the leading-edge suction for the same total thrust; however, a sweep angle of the leading edge ... |
format |
Article in Journal/Newspaper |
author |
Chopra, M. G. Kambe, T. |
spellingShingle |
Chopra, M. G. Kambe, T. Hydromechanics of lunate-tail swimming propulsion. Part 2 |
author_facet |
Chopra, M. G. Kambe, T. |
author_sort |
Chopra, M. G. |
title |
Hydromechanics of lunate-tail swimming propulsion. Part 2 |
title_short |
Hydromechanics of lunate-tail swimming propulsion. Part 2 |
title_full |
Hydromechanics of lunate-tail swimming propulsion. Part 2 |
title_fullStr |
Hydromechanics of lunate-tail swimming propulsion. Part 2 |
title_full_unstemmed |
Hydromechanics of lunate-tail swimming propulsion. Part 2 |
title_sort |
hydromechanics of lunate-tail swimming propulsion. part 2 |
publisher |
Cambridge University Press (CUP) |
publishDate |
1977 |
url |
http://dx.doi.org/10.1017/s0022112077000032 https://www.cambridge.org/core/services/aop-cambridge-core/content/view/S0022112077000032 |
genre |
Porbeagle |
genre_facet |
Porbeagle |
op_source |
Journal of Fluid Mechanics volume 79, issue 1, page 49-69 ISSN 0022-1120 1469-7645 |
op_rights |
https://www.cambridge.org/core/terms |
op_doi |
https://doi.org/10.1017/s0022112077000032 |
container_title |
Journal of Fluid Mechanics |
container_volume |
79 |
container_issue |
1 |
container_start_page |
49 |
op_container_end_page |
69 |
_version_ |
1802649353579397120 |