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First published online March 14, 2005
Journal of Experimental Biology 208, iii (2005)
Copyright © 2005 The Company of Biologists Limited
doi: 10.1242/jeb.01536

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Inside JEB

PUZZLING PROPULSION

Yfke van Bergen

yfke{at}biologists.com

Watching ideal smoke rings in their laboratories, engineers with an interest in biology have often wondered whether squid use vortex ring propulsion to glide around their aquatic homes. But Mark Grosenbaugh and Erik Anderson of Woods Hole suspected that something quite different was going on, and set out to examine squid locomotion. It all began with an innocent equation for the ideal smoke ring: L/D=4, meaning that an ideal vortex ring results if the length of a fluid jet is four times the diameter of the pipe emitting the fluid. From his previous work, Anderson knew that this wasn't true for squid pushing water out of their 1 cm-wide jet nozzle. To settle the matter, Anderson and Grosenbaugh applied advanced strobe photography to the extremely tricky problem of visualising squid jet flow (p. 1125).

To see the flow of water behind steadily swimming squid, they placed microscopic silver-coated spheres into the water and illuminated them with a sheet of laser light. Pointing a digital camera at the light-reflecting spheres, they compared successive frames to see exactly how the spheres, and therefore the water, moved as squid swam through a flume. Anderson and Grosenbaugh saw that squid don't puff along on individual vortex rings, but instead eject a prolonged fluid jet that is normally 8 to 34 times the diameter of the squid's jet nozzle.

"But the `Aha!' moment really came when we realised that the background flow of water past the squid tends to discourage vortex ring propulsion in steady swimming," Anderson says. He explains that most previous research examined jet flow issued into stationary water, but clearly, water flowing around the squid in its natural home influences jet structure. Ultimately, Anderson says, `all that's important is what the data tell us is really happening in nature. What may be ideal from an engineering standpoint may not be ideal for a particular niche. Our work illustrates the need to let biology speak for itself, especially in biomechanics.'

References

Anderson, E. J. and Grosenbaugh, M. A. (2005). Jet flow in steadily swimming adult squid. J. Exp. Biol. 208,1125 -1146.[Abstract/Free Full Text]

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Related articles in JEB:

Jet flow in steadily swimming adult squid

Erik J. Anderson and Mark A. Grosenbaugh
JEB 2005 208: 1125-1146. [Abstract] [Full Text]  

This Article Full Text (PDF) Alert me when this article is cited Alert me if a correction is posted Services Email this article to a friend Related articles in JEB Similar articles in this journal Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via Google Scholar Google Scholar Articles by van Bergen, Y. Search for Related Content PubMed Articles by van Bergen, Y. Social Bookmarking                         What's this?