Michael S. Triantafyllou and George S.
Massachusetts Institute of Technology
These researchers at MIT and CCNY have built a detailed replica of a bluefin
tuna to study how fish propel themselves so efficiently. They found that the
efficiency is closely tied up with the way the vortices are arrange in the wake.
The shedding of vortices is described by a non-dimensional frequence, called the
Strouhal number, defined as given in the caption. As is shown, a lrge number of fish and other animals swim at a Strouhal number
of about 0.3.
Picture taken from the article "An Efficient Swimming Machine," by Michael S.
Triantafyllou and George S. Triantafyllou, Scientific American, March 1995.