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Aquatic vertebrate locomotion: wakes from body waves
J J Videler1, U K Müller, E J Stamhuis
1Department of Marine Biology, Groningen University, The Netherlands. j.j.videler@biol.rug.nl
The Journal of Experimental Biology
|November 24, 1999
Summary
Fish swimming creates vortices from body waves and tail beats. The interaction between these body and tail vortices shapes the wake and influences thrust generation, with two distinct wake patterns observed.
Area of Science:
- Biomechanics
- Fluid dynamics
- Locomotion
Background:
- Swimming vertebrates utilize body and tail undulations, characterized by traveling inflection points where body curvature reverses.
- These movements generate semicircular flows, termed proto-vortices, which propagate along the body towards the tail.
Purpose of the Study:
- To investigate the relationship between body wave shape, inflection points, proto-vortex formation, and vortex shedding in aquatic locomotion.
- To understand how the interaction between body and tail vortices influences wake structure and propulsive efficiency.
Main Methods:
- Experimental observation of swimming vertebrates to analyze body wave dynamics and fluid flow patterns.
- Phase analysis correlating tailbeat cycles with inflection point and proto-vortex progression.
Main Results:
- Proto-vortices are shed as body vortices at the tail, synchronized with inflection points reaching the tail tip.
- The phase relationship between proto-vortex shedding and tailbeats dictates body-tail vortex interaction.
- Two distinct wake types were identified: a two-vortex wake (enhanced tail vortex) and a four-vortex wake (separate body and tail vortices).
Conclusions:
- The fish's body wave shape controls vortex shedding, influencing wake structure and thrust.
- The interaction between body and tail vortices is crucial for understanding aquatic locomotion and wake dynamics.
- The functional significance of the observed four-vortex wake pattern remains an open question.