Hydrodynamical effect of parallelly swimming fish using computational fluid dynamics method.

Fish form schools because of many possible reasons. However, the hydrodynamic mechanism whereby the energy efficiency of fish schools is improved still remains unclear. There are limited examples of fish models based on actual swimming movements using simulation, and the movements in existing models...

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Main Authors: Keisuke Doi, Tsutomu Takagi, Yasushi Mitsunaga, Shinsuke Torisawa
Format: Article
Language:English
Published: Public Library of Science (PLoS) 2021-01-01
Series:PLoS ONE
Online Access:https://journals.plos.org/plosone/article/file?id=10.1371/journal.pone.0250837&type=printable
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author Keisuke Doi
Tsutomu Takagi
Yasushi Mitsunaga
Shinsuke Torisawa
author_facet Keisuke Doi
Tsutomu Takagi
Yasushi Mitsunaga
Shinsuke Torisawa
author_sort Keisuke Doi
collection DOAJ
description Fish form schools because of many possible reasons. However, the hydrodynamic mechanism whereby the energy efficiency of fish schools is improved still remains unclear. There are limited examples of fish models based on actual swimming movements using simulation, and the movements in existing models are simple. Therefore, in this study, we analyzed the swimming behavior of Biwa salmon (Oncorhynchus sp., a salmonid fish) using image analyses and formulated its swimming motion. Moreover, computational fluid dynamics analysis was carried out using the formulated swimming motion to determine the fluid force acting on the fish body model with real fish swimming motion. The swimming efficiency of the fish model under parallel swimming was obtained from the calculated surrounding fluid force and compared for different neighboring distances. The flow field around the fish model was also examined. The swimming efficiency of two fish models swimming parallelly was improved by approximately 10% when they were separated by a distance of 0.4L, where L is the total length of the model. In addition, the flow field behind the fish body was examined under both inphase and antiphase conditions and at inter-individual distances of 0.8L and 1.2L. The apparent flow speed in the distance range of 0.5-2.0L from the midpoint of the snouts of the two individuals was lower than the swimming speed. The pressure distribution on the fish model showed an elevated pressure at the caudal fin. Interestingly, we obtained an isopleth map similar to that of a caudal peduncle. To avoid a negative thrust, the aft part of the body must be thin, as shown in the isopleth map obtained in this study.
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spelling doaj-art-5e343c6143d64a2894fc20dd911dc44e2025-08-20T02:54:29ZengPublic Library of Science (PLoS)PLoS ONE1932-62032021-01-01165e025083710.1371/journal.pone.0250837Hydrodynamical effect of parallelly swimming fish using computational fluid dynamics method.Keisuke DoiTsutomu TakagiYasushi MitsunagaShinsuke TorisawaFish form schools because of many possible reasons. However, the hydrodynamic mechanism whereby the energy efficiency of fish schools is improved still remains unclear. There are limited examples of fish models based on actual swimming movements using simulation, and the movements in existing models are simple. Therefore, in this study, we analyzed the swimming behavior of Biwa salmon (Oncorhynchus sp., a salmonid fish) using image analyses and formulated its swimming motion. Moreover, computational fluid dynamics analysis was carried out using the formulated swimming motion to determine the fluid force acting on the fish body model with real fish swimming motion. The swimming efficiency of the fish model under parallel swimming was obtained from the calculated surrounding fluid force and compared for different neighboring distances. The flow field around the fish model was also examined. The swimming efficiency of two fish models swimming parallelly was improved by approximately 10% when they were separated by a distance of 0.4L, where L is the total length of the model. In addition, the flow field behind the fish body was examined under both inphase and antiphase conditions and at inter-individual distances of 0.8L and 1.2L. The apparent flow speed in the distance range of 0.5-2.0L from the midpoint of the snouts of the two individuals was lower than the swimming speed. The pressure distribution on the fish model showed an elevated pressure at the caudal fin. Interestingly, we obtained an isopleth map similar to that of a caudal peduncle. To avoid a negative thrust, the aft part of the body must be thin, as shown in the isopleth map obtained in this study.https://journals.plos.org/plosone/article/file?id=10.1371/journal.pone.0250837&type=printable
spellingShingle Keisuke Doi
Tsutomu Takagi
Yasushi Mitsunaga
Shinsuke Torisawa
Hydrodynamical effect of parallelly swimming fish using computational fluid dynamics method.
PLoS ONE
title Hydrodynamical effect of parallelly swimming fish using computational fluid dynamics method.
title_full Hydrodynamical effect of parallelly swimming fish using computational fluid dynamics method.
title_fullStr Hydrodynamical effect of parallelly swimming fish using computational fluid dynamics method.
title_full_unstemmed Hydrodynamical effect of parallelly swimming fish using computational fluid dynamics method.
title_short Hydrodynamical effect of parallelly swimming fish using computational fluid dynamics method.
title_sort hydrodynamical effect of parallelly swimming fish using computational fluid dynamics method
url https://journals.plos.org/plosone/article/file?id=10.1371/journal.pone.0250837&type=printable
work_keys_str_mv AT keisukedoi hydrodynamicaleffectofparallellyswimmingfishusingcomputationalfluiddynamicsmethod
AT tsutomutakagi hydrodynamicaleffectofparallellyswimmingfishusingcomputationalfluiddynamicsmethod
AT yasushimitsunaga hydrodynamicaleffectofparallellyswimmingfishusingcomputationalfluiddynamicsmethod
AT shinsuketorisawa hydrodynamicaleffectofparallellyswimmingfishusingcomputationalfluiddynamicsmethod