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Swimming mechanism of a dolphin on the basis of the hierarchy of vortices

Yutaro Motoori*, Hideki Murahata, and Susumu Goto†

  • Graduate School of Engineering Science, the University of Osaka, 1-3 Machikaneyamacho, Toyonaka, Osaka 560-8531, Japan

  • *Contact author: y.motoori.es@osaka-u.ac.jp
  • †Contact author: s.goto.es@osaka-u.ac.jp
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Phys. Rev. Fluids 11, L042601 – Published 30 April, 2026

DOI: https://doi.org/10.1103/tnxb-ckr5

Abstract

Swimming dolphins generate fully developed turbulence. In the present study, we demonstrate that the hierarchy of multiscale vortices existing in the turbulence is key to understanding how dolphins swim. For this demonstration, we conduct direct numerical simulations of a self-propelled dolphin using a simple model, and examine the role of multiscale vortices in propulsion. By decomposing the turbulent flow into different scales, we elucidate how the dolphin generates the hierarchy of multiscale vortices. Large vortex rings, which are shed due to the oscillation of the caudal fin, produce significant propulsion, while smaller vortices are created through the energy cascade, contributing little to the propulsion. We also demonstrate that the role of these vortices in the propulsion remains robust regardless of the Reynolds number.

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Phys. Rev. Fluids 11, L042601– Published 30 April, 2026
  • Received 17 November 2025
  • Accepted 10 March 2026
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