In order to breed, many salmon species swim upstream, facing turbulent waters along the way. How are they able to endure a grueling journey without succumbing to exhaustion? Instead of being overwhelmed by the rough water, these fish actually take advantage of it. How?
Consider: Salmon do not plow through chaotic water. Instead, when swimming upstream, they conserve energy by using vortices, or miniature whirlpools, that form where the water flow is disturbed by rocks, branches, or other objects. As the vortices form on alternating sides of an object, the fish curve their bodies from side to side and glide between the pockets of turbulence. (See diagram.)
use the vortices created by the
fish swimming in front of
them, effectively riding in their
wake. The fish can even take
advantage of the turbulence
created by their own bodies!
Researchers hope to borrow from the salmon’s
efficient swimming style to harvest energy
from slow-moving water. Traditional hydropower
equipment usually generates electricity
in water flowing at a rate of about five knots
(5.8 miles per hour [9.3 km/h]) or faster. Now
a prototype using vortex-induced vibrations can
generate electricity from water creeping along
at only two knots. The technology, however, is
nowhere near the level of sophistication found
in such fish as salmon. Professor Michael Bernitsas
of the University of Michigan, U.S.A., admits:
“We are not as smart as fish at this point.”
What do you think? Did the
salmon’s ability to harness energy
from water turbulence come
about by chance? Or was it designed?
This seems promising, since most of
the earth’s water currents move slower than
three knots.
[As appeared in the magazine Awake!, December 2010]