Experimental study of body-fin interaction and vortex dynamics generated by a two degree-of-freedom fish model

Seth A. Brooks, Melissa A. Green

Research output: Contribution to journalArticlepeer-review


Oscillatory modes of swimming are used by a majority of aquatic swimmers to generate thrust. This work seeks to understand the phenomenological relationship between the body and caudal fin for fast and efficient thunniform swimming. Phase-averaged velocity data was collected and analyzed in order to understand the effects of body-fin kinematics on the wake behind a two degree-of-freedom fish model. The model is based on the yellowfin tuna (Thunnus albacares) which is known to be both fast and efficient. Velocity data was obtained along the side of the tail and caudal fin region as well as in the wake downstream of the caudal fin. Body-generated vortices were found to be small and have an insignificant effect on the caudal fin wake. The evolution of leading edge vortices formed on the caudal fin varied depending on the body-fin kinematics. The circulation produced at the trailing edge during each half-cycle was found to be relatively insensitive to the freestream velocity, but also varied with body-fin kinematics. Overall, the generation of vorticity in the wake was found to dependent on the trailing edge motion profile and velocity. Even relatively minor deviations from the commonly used model of sinusoidal motion is shown to change the strength and organization of coherent structures in the wake, which have been shown in the literature to be related to performance metrics such as thrust and efficiency.

Original languageEnglish (US)
Article number67
Issue number4
StatePublished - Dec 1 2019
Externally publishedYes

Bibliographical note

Funding Information:
This work was supported by the Office of Naval Research under ONR Award No. N00014-17-1-2759. The authors also wish to thank the Syracuse Center of Excellence for Environmental and Energy Systems for providing funds used towards the purchase of lasers and related equipment. The authors would like to thank Bill Dossert, Phil Arnold, and Lou Buda for the construction of the model and their help with model design. The images in Figure 6 were created using FieldView as provided by Intelligent Light through its University Partners Program.

Publisher Copyright:
© 2019 by the authors.


  • Bio-propulsion
  • Biological fluid dynamics
  • Body-fin interaction
  • Circulation production
  • Fish
  • Leading edge vortices
  • Nonsinusoidal motion
  • Swimming
  • Vortex dynamics


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