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#Post#: 915--------------------------------------------------
Swiming Efficiency of Aquatic Animals Far exceeds the Propeller
DIR By: AGelbert
Date: April 11, 2014, 8:39 pm
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[move]Gray's "Paradox" was nothing but human ignorance.
;D[/move]
Fluke Forces
Dolphins prove that they rely on muscle power, rather than a
trick of fluid dynamics, to race through water at high speeds.
By Dan Cossins | April 1, 2014
MIGHTY FLIPPERS: Dolphins are able to swim so rapidly by
generating large amounts of power from the oscillations of their
flukes.
Writing in the Journal of Experimental Biology in 1936, British
zoologist James Gray made a simple calculation based on
observations of a dolphin swimming alongside a ship in the
Indian Ocean. The dolphin, he reported, had passed the vessel,
from stern to bow, in 7 seconds. The ship was 41 meters long and
it was moving at 8.5 knots. “This dolphin must therefore have
been travelling at 20 knots [10.1 meters per second],” wrote
Gray, who concluded, after an avalanche of more complex
calculations, that dolphins couldn’t possibly have attained that
speed using muscle power alone.
In an attempt to resolve the quandary, which became known as
“Gray’s paradox,” he suggested that dolphins must use some trick
of fluid dynamics to overcome drag, the opposing forces acting
on any body moving through a fluid. And despite the fact that
he’d made several erroneous assumptions, Gray’s paradox lived
on, spurring others to search for the dolphin’s drag-reducing
secret. During the Cold War, military researchers in the U.S.
and the Soviet Union went after the mysterious mechanism in the
hope that it might provide inspiration for faster, deadlier
submarines and torpedoes.
Frank Fish, a biologist at West Chester University in
Pennsylvania who studies the biomechanics of aquatic mammals,
read such tales with interest. “To resolve the paradox was to
assume that flow over the dolphin’s body is laminar, meaning
that the particles all move parallel to one another and to the
skin, when everything said it would be turbulent,” says Fish.
“The argument brought forth ideas that the dolphin has some
adaptations in the skin to smooth out the flow.”
But Fish was never convinced. Instead, he believed that
dolphins’ muscular tails and flexible, wing-like flukes produce
ample propulsive force to swim as fast as they do, without the
need for any enigmatic hydrodynamic adaptation.
In 1993, Fish used a hydrodynamic model to show as much (J Exp
Biol, 185:179-93, 1993). But the point was difficult to prove
because it was impossible to directly measure the thrust
produced by free-swimming dolphins. For small fish, researchers
use a method called digital particle image velocimetry (DPIV). A
tank is filled with water and glass microbeads, a thin layer of
which is illuminated with a sheet-like laser beam. Using a
high-speed video camera to film how the beads move as the fish
swims through, researchers can visualize the jets and vortices
its motion creates. Then, once the footage is separated into
successive frames and digitized, the investigators apply an
algorithm to figure out the propulsive forces generated. The
problem is, says Fish, “there’s no chance anyone would let you
throw in glass beads and shine laser beams at dolphins. It’s way
too risky.”
WHAT A WAKE: As a dolphin swims through a bubble curtain, its
powerful fluke generates vortices (picture at link) that can be
filmed and analyzed using digital particle image velocimetry.
Fish was stuck. But then he met Timothy Wei at an informal
hydrodynamics meeting at Princeton University in 2005. Wei, now
an engineer at the University of Nebraska, had been measuring
the propulsive power of Olympic swimmers by asking them to swim
through a curtain of air bubbles. “It was perfect,” says Fish.
The bubbles reflect light, so no lasers are required, and there
is no need to worry about swallowing air bubbles. “All we needed
now were the dolphins,” Fish adds. So he called up longtime
friend and collaborator Terrie Williams, an animal physiologist
at the University of California, Santa Cruz (UCSC), who works
with two captive bottlenose dolphins named Primo and Puka.
HTML http://farm1.staticflickr.com/156/400424413_fd71a43fe4.jpg
Primo and Puka
The team laid 6 meters of fine-pored garden-soaker hose in a
straight line along the floor of a large outdoor pool at UCSC’s
Long Marine Laboratory and hooked it up to a SCUBA tank of
compressed air to generate bubbles. The group filmed the bubbles
as Primo and Puka, after some gentle persuasion from their
trainers, swam through the 2-cm-wide bubble curtain, churning up
the bubbles with their flukes as they went. “The hardest thing
was to get them to stop investigating the bubbles or us,” says
Fish. “They’re very curious animals.”
After processing the data with DPIV software, Wei and Fish
worked out that the dolphins generated up to 2,380 watts, or 3.2
horsepower, of thrust when swimming steadily at 3.4 meters per
second and up to a whopping 5,400 watts, or 7.2 horsepower, when
accelerating from rest (J Exp Biol, 217:252-60, 2014). Fish also
calculated that “the dolphins were actually incurring a heavy
drag load, suggesting they don’t have any special drag-reduction
tricks.” Just as he’d thought, dolphins generate enough power to
overcome their drag. “So the idea of Gray’s paradox, in which
the dolphin doesn’t have enough muscle to maintain a high speed,
falls apart.”
Ann Pabst, an animal physiologist at the University of North
Carolina Wilmington who was not involved in the work, is
impressed by the authors’ strategy. “[They] figured out a very
clever method to tap into the power of DPIV . . . but to do so
in a way that was safe for these protected animals,” she told
The Scientist in an e-mail. “Replacing lasers and neutrally
buoyant particles with sunlight and air bubbles was ingenious.”
The study, says Pabst, “will be the final nail in the lid [for
Gray’s paradox].”
And because it appears that dolphins incur high levels of drag,
the idea that their skin holds the secret to achieving laminar
flow looks like a red herring. “We should certainly stop looking
for special fluid dynamics–based trickery in the flow over
swimming dolphins,” says Harvard biologist George Lauder, who
studies fish hydrodynamics but was not part of the study. “There
is no more trickery there than is present over the body of any
swimming fish.”
HTML http://www.the-scientist.com//?articles.view/articleNo/39481/title/Fluke-Forces/
#Post#: 2257--------------------------------------------------
Re: Swiming Efficiency of Aquatic Animals Far exceeds the
Propeller
DIR By: AGelbert
Date: November 25, 2014, 7:49 pm
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HTML http://www.createaforum.com/gallery/renewablerevolution/3-251114204638.png
[center]
HTML http://www.pic4ever.com/images/looksmiley.gif
[/center]
HTML https://www.youtube.com/watch?v=aVbQ4yQG64A&feature=player_embedded
Watch lots of migrating crabs along with fish and seals on
camera.
#Post#: 2620--------------------------------------------------
Re: Swiming Efficiency of Aquatic Animals Far exceeds the
Propeller
DIR By: AGelbert
Date: January 29, 2015, 1:50 pm
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Sea Turtles Have an Internal ‘GPS’ That Uses Earth’s Magnetic
Field
by TreeHugger
January 26, 2015 9:00 am
HTML http://www.createaforum.com/gallery/renewablerevolution/3-290115140700.jpeg
Written by Michael Graham Richard
Many animals have a talent for finding their way around the
globe that any of us who gets lost doing a short trip can’t help
but envy. From birds who go back and forth across continents,
following the seasons, to the beautiful sea turtles that can
find the specific beach where they were born years before to, in
turn, lay their eggs. For decades, scientists have wondered how
the turtles did it, and it seems like we might finally have an
answer thanks to a study conducted at the University of North
Carolina at Chapel Hill.
HTML http://www.createaforum.com/gallery/renewablerevolution/3-290115140742.jpeg
Photo Credit: Les_Williams / Flickr
“Sea turtles migrate across thousands of miles of ocean before
returning to nest on the same stretch of coastline where they
hatched, but how they do this has mystified scientists for more
than fifty years,” said J. Roger Brothers of the University of
North Carolina at Chapel Hill. “Our results provide evidence
that turtles imprint on the unique magnetic field of their natal
beach as hatchlings and then use this information to return as
adults.”
To prove that this is the case, the researchers compared 19
years of data on Loggerhead Sea Turtle migration on the Eastern
coast of Florida with data on naturally occurring local changes
in the Earth’s magnetic field. The scientists found a strong
association between the spatial distribution of turtle nests and
subtle shifts in the Earth’s magnetic field.
The effect went both ways: When the magnetic fields shifted in
such a way that adjacent locations along the beach moved closer,
the turtles came back to nest closer together, spreading over a
shorter stretch of the coast. When the magnetic signature of
certain spots moved apart, the turtles spread out over a longer
stretch.
Little is known about how turtles detect the geomagnetic field,
[b]but at least we can now show with a fair amount of certainty
that they use it.
HTML http://www.pic4ever.com/images/128fs318181.gif[/b]
But why have sea turtles evolved ::) to go nest where they
themselves hatched? It’s all about finding the right conditions;
soft sand, the right temperature, few predators and an easily
accessible beach.
“The only way a female turtle can be sure that she is nesting in
a place favorable for egg development is to nest on the same
beach where she hatched,” Brothers said. “The logic of sea
turtles seems to be that ‘if it worked for me, it should work
for my offspring.’”
HTML http://www.createaforum.com/gallery/renewablerevolution/3-290115140944.jpeg
Photo Credit: Les_Williams / Flickr
And yes, I’m aware that the Global Positioning System (GPS) that
we use to get around doesn’t use magnetic fields, but rather
Einstein’s relativity (there’s an explanation here). Using it in
the title was just short-hand for a way to navigate to your
destination.
Via Journal of Current Biology, Livescience
This post originally appeared on TreeHugger.
[b]Agelbert NOTE: [/b] The following comment was even more
interesting than the article!
HTML http://www.pic4ever.com/images/reading.gif
Enjoy.
Beverly S.
3:31PM PST on Jan 27, 2015
Many, if not all animals have an amazing sense of direction. I
remember reading that we humans also have a "compass" in our
noses, so I did a little research. Interesting!
Some years ago scientists at CALTECH (California Institute of
Technology in Pasadena) discovered that humans possess a tiny,
shiny crystal of magnetite in the ethmoid bone, located between
your eyes, just behind the nose. :o
HTML http://www.pic4ever.com/images/8.gif
HTML http://legacy.owensboro.kctcs.edu/gcaplan/anat/notes/Image525.gif
Magnetite is a magnetic mineral also possessed by homing
pigeons, migratory salmon, dolphins, honeybees, and bats.
Indeed, some bacteria even contain strands of magnetite that
function, according to Dr. Charles Walcott of the Cornell
Laboratory of Ornithology in Ithaca, New York, "as tiny compass
needles, allowing them [the bacteria] to orient themselves in
the earth's magnetic field and swim down to their happy home in
the mud".
It seems that magnetite helps direction finding in animals and
helps migratory species migrate successfully by allowing them to
draw upon the earth's magnetic fields. But scientists are not
sure how they do this.
In any case, when it comes to humans, according to some experts,
magnetite makes the ethmoid bone sensitive to the earth's
magnetic field and helps your sense of direction.
Stephen Juan, Ph.D. is an anthropologist at the University of
Sydney
Read more:
HTML http://www.treehugger.com/natural-sciences/no-place-like-magnetic-home-sea-turtles-gps-earth-magnetic-field.html#ixzz3QBWvIzs4
Agelbert NOTE: Have we lost our PREVIOUS ability to follow
earth's magnetic fields through "use it or lose it" SUBTRACTION
of genetic material otherwise known as NATURAL SELECTION? Only
your Darwinian Evolutionist knows - and they don't want to go
there. Admiting we are LESS "evolved" than we previously were
is a NO NO in Darwinian circles. ;D
#Post#: 4020--------------------------------------------------
Re: Swiming Efficiency of Aquatic Animals Far exceeds the
Propeller
DIR By: AGelbert
Date: October 18, 2015, 4:24 pm
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A case in nature where the parent doesn't argue with its
offspring. ;)
[center]
HTML https://33.media.tumblr.com/tumblr_m00egxAyJY1qbabg0.png[/center]
[center]Pseudis paradoxa (Paradoxical Frog) [/center]
[center]
Where Does the Paradoxical Frog Get Its Name?[/center]
The paradoxical frog is a South American frog also known as the
“shrinking frog” because of the enormous size of its tadpoles
compared with the adult frog. The tadpoles can reach more than
eight inches in length, while the adult frogs are generally only
two inches long.
While an ordinary tadpole transforming into a frog will simply
grow legs as its tail shrinks, the tadpoles of the paradoxical
frog need to shrink their entire body to grow up. :o
Several other species of frogs have similarly large larvae, but
they all spend winter as tadpoles and need greater size to
survive. Tadpoles of paradoxical frogs are not subjected to the
same conditions and scientists are unsure exactly why they grow
so large.
HTML http://www.pic4ever.com/images/34y5mvr.gif
[center]
More about frogs:[/center]
[center]
HTML https://upload.wikimedia.org/wikipedia/commons/thumb/1/14/Pseudis_paradoxa01a.jpg/220px-Pseudis_paradoxa01a.jpg[/center]
[center]Pseudis paradoxa (Paradoxical Frog) enjoying life in
some duckweed. [/center]
The paradoxical frog produces a skin secretion which could be
used to help combat diabetes by stimulating insulin production.
While all frogs go through a tadpole stage, not all tadpoles
live in fresh water. For example, Darwin's frog tadpoles mature
while contained inside the vocal sac of their father.
The largest frog species is the Goliath frog, which can grow to
over a foot long and weigh up to seven pounds. :o
[center]
HTML http://i.ytimg.com/vi/SlQYQjcFszA/hqdefault.jpg[/center]
[center]Conraua goliath (Goliath Frog) [/center]
No relationship to Jabba the Hutt is claimed. ;D
HTML http://www.wisegeek.com/where-does-the-paradoxical-frog-gets-it-name.htm
HTML http://www.wisegeek.com/where-does-the-paradoxical-frog-gets-it-name.htm
#Post#: 4376--------------------------------------------------
Re: Swiming Efficiency of Aquatic Animals Far exceeds the
Propeller
DIR By: AGelbert
Date: January 20, 2016, 10:10 pm
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SLIDESHOW: Meet the Penguins!
[center]
HTML http://www.marylandzoo.org/assets/penguinawarenessfeature.jpg[/center]
Celebrate Penguin Awareness Day
January 20th is Penguin Awareness Day and what better time to
celebrate these amazing birds? Penguins delight and charm nature
lovers of all ages. But, many penguin species face serious,
human-caused threats. Here, you'll meet 9 penguin species and
learn what they're facing
HTML http://support.edf.org/site/PageServer?pagename=meet_the_penguins&autologin=true&utm_source=EDF%20action%20network&utm_campaign=edf_slideshows_upd_mem&utm_medium=email-49836&utm_id=1453265711
[center]
HTML http://www.clipartbest.com/cliparts/xig/ojx/xigojx6KT.png[/center]
#Post#: 10959--------------------------------------------------
Re: Swiming Efficiency of Aquatic Animals Far exceeds the
Propeller
DIR By: AGelbert
Date: October 26, 2018, 1:03 pm
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HTML http://renewablerevolution.createaforum.com/gallery/renewablerevolution/3-061217183404.png
[center]'Ghostly' Dumbo Octopus 🐙 Makes Hypnotizing
Appearance in New Deep-Sea Footage[/center]
Catie Keck
Yesterday 12:49amFiled to: SCIENCE
[center]
HTML https://youtu.be/ayCdTH7k6eU[/center]
Article with above video:
HTML http://www.createaforum.com/gallery/renewablerevolution/3-060914180936.jpeg
HTML https://earther.gizmodo.com/ghostly-dumbo-octopus-makes-hypnotizing-appearance-in-1829986443
#Post#: 12274--------------------------------------------------
Re: Swiming Efficiency of Aquatic Animals Far exceeds the
Propeller
DIR By: AGelbert
Date: May 4, 2019, 1:50 pm
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[center]
HTML https://cdn.zmescience.com/wp-content/uploads/2015/04/Octopus-Arms-Think-for-Themselves-379020-2.jpg[/center]
[center]Do All Octopuses Have Eight Arms? 🤔[/center]
There are around 300 known octopus species in the world. Those
odd-looking creatures from the deep sea, adorned with
sucker-lined limbs and an elongated body resembling a bulbous
head, were portrayed as sea monsters in mythology, especially in
the legends of Norway and Greece. In 1818, English biologist
William Leach gave their order the scientific name Octopoda.
Contrary to popular belief, though, they do not have eight arms.
They actually have six arms and two legs, a team of European
scientists at Sea Life aquariums reported in 2008. The two
rearmost limbs act as legs, propelling the octopus efficiently
across the ocean floor.
🐙Octopuses get a leg up:
֍ Researchers explained that they use their two rear limbs
“to get around over rocks and the seabed. They also use these
two legs to push off when they wish to swim, and then other
tentacles are used to propel them.”
֍ The purpose of the study was to see if octopuses favored
one side or the other. The researchers found that octopuses are
ambidextrous. In addition, they found that many octopuses use
the third arm from the front to eat.
HTML http://edition.cnn.com/video/world/2010/10/26/paul.octopus.obit.nat.cnn.640x360.jpg
[center]🌟 Paul the Octopus[/center]
֍ At a Sea Life Centre in Oberhausen, Germany, Paul the
Octopus became a soccer sensation when he correctly predicted
numerous games in UEFA Euro 2008 and the 2010 World Cup --
including correctly picking Spain as the winner of the World Cup
final. :o
HTML http://renewablerevolution.createaforum.com/gallery/renewablerevolution/1/3-210818163124-1669950.gif
HTML https://www.wisegeek.com/do-all-octopuses-have-eight-arms.htm
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