Swimming efficiency and flow field around fish in school

2022 Fiscal Year Final Research Report

• Project/Area Number: 20K04355
• Research Category: Grant-in-Aid for Scientific Research (C)
• Allocation Type: Multi-year Fund
• Section: 一般
• Review Section: Basic Section 20010:Mechanics and mechatronics-related
• Research Institution: Kindai University
• Principal Investigator: Torisawa Shinsuke 近畿大学, 農学部, 講師 (80399097)
• Co-Investigator(Kenkyū-buntansha): 竹原 幸生 近畿大学, 理工学部, 教授 (50216933) ; 高木 力 北海道大学, 水産科学研究院, 教授 (80319657)
• Project Period (FY): 2020-04-01 – 2023-03-31
• Keywords: バイオメカニクス / 魚群行動 / PTV(流体可視化計測)解析 / CFD(数値流体力学)解析 / エネルギーコスト

Outline of Final Research Achievements

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.

Free Research Field

水産学・漁業学

Academic Significance and Societal Importance of the Research Achievements

地球規模での漁業資源水準の低下を背景に，賢く獲る漁業技術の開発が求められているが，生産手段の最適化は対象生物(魚類)の行動特性を理解せずには実現できない。従って，魚類の群行動についての基本的理解とその研究は不可欠である。
本研究では，魚類が群れを形成する意味を物理的側面からアプローチし，その本質的意義の解明を目指す。背景となる力学的論理基盤から群を形成したことによる移動エネルギーコストの利得が単一個体よりどの程度アドバンテージとなり，魚群の配置によりどのような差がでてくるのかを明らかにする。これをベースに，種の違いにより魚群の移動距離，移動速度と移動エネルギーコストの適値と限界が明らかになる。