Dolphins are simply much stronger than anyone had guessed
Using new technology, Timothy Wie and his team at Rensselear have solved a 72-year-old puzzle about how dolphins swim. "Gray's Paradox" Solved: Researchers Discover Secret of Speedy Dolphins announces a Rensselear press release dated November 24, 2008. The image with this post is from the a video available at the Rensselear project.
From the point of view of education resources, discoveries like the dolphin kick show off the power of the internet to deliver the most current knowledge to students and teachers. The modules below point to expert knowledge related to the dolphin power kick discovery.
From the point of view of education resources, discoveries like the dolphin kick show off the power of the internet to deliver the most current knowledge to students and teachers. The modules below point to expert knowledge related to the dolphin power kick discovery.
Here is what the Rensselear team learned about dolphin power kicks
This new understanding solved the paradox that muscles would not be strong enough for the power of the dolphin's kick
The Rensselear press release provides this information on just how (very!) strong the flapping fluke of a dolphin is:
Wei also used this technique to film dolphins as they were doing tail-stands, a trick where the dolphins "walk" on water by holding most of their bodies vertical above the water while supporting themselves with short, powerful thrusts of their tails.
The results show that dolphins produce on average about 200 pounds of force when flapping their tail - about 10 times more force than Gray originally hypothesized.
"It turns out that the answer to Gray's Paradox had nothing to do with the dolphins' skin," Wei said. "Dolphins can certainly produce enough force to overcome drag. The scientific community has known this for a while, but this is the first time anyone has been able to actually quantitatively measure the force and say, for certain, the paradox is solved."
At peak performance, the dolphins produced between 300 and 400 pounds of force. Human Olympic swimmers, by comparison, peak at about 60 to 70 pounds of force, Wei said. He knows this for a fact because he has been working with U.S.A. Swimming over the past few years to use these same bubble-tracking DPIV and force-measuring techniques to better understand how elite swimmers interact with the water, and improve lap times.
Wei also used this technique to film dolphins as they were doing tail-stands, a trick where the dolphins "walk" on water by holding most of their bodies vertical above the water while supporting themselves with short, powerful thrusts of their tails.
The results show that dolphins produce on average about 200 pounds of force when flapping their tail - about 10 times more force than Gray originally hypothesized.
"It turns out that the answer to Gray's Paradox had nothing to do with the dolphins' skin," Wei said. "Dolphins can certainly produce enough force to overcome drag. The scientific community has known this for a while, but this is the first time anyone has been able to actually quantitatively measure the force and say, for certain, the paradox is solved."
At peak performance, the dolphins produced between 300 and 400 pounds of force. Human Olympic swimmers, by comparison, peak at about 60 to 70 pounds of force, Wei said. He knows this for a fact because he has been working with U.S.A. Swimming over the past few years to use these same bubble-tracking DPIV and force-measuring techniques to better understand how elite swimmers interact with the water, and improve lap times.
Dolphin Boundary Layer %u2014 the latest science before the new discovery
This YouTube video dated April 24, 2007, and based on work at Scripps Institution of Oceanography, describes theories about dolphin speed before the discovery at Rensselear in 2008.
Explanation from the video: James Gray, an English Zoologist discovered that dolphins managed to attain speeds in the water that exceeded the power limit calculated for their muscles by a factor of seven. This paradox led researchers to investigate what phenomena accounted for this apparent discrepancy between hydrodynamic theory and physical observation. While some have questioned Gray's calculations, others like Jim Rohr at the University of California in San Diego have sought answers to this paradox by studying the fluid dynamics. Using bioluminescent dinoflagellates as visual signals and enhanced video recording equipment, he was able to assess the boundary layer over the dolphins body surface at speeds of 2 m/s. These organisms give off light when the fluid layers around them are subject to stresses %u03C4wall%u22480.1Nm%u22122. He then studied the enhanced recordings and proposed a solution to Gray's paradox. Research revealed that the dinoflagellates failed to light up in regions on the dolphin's body where the boundary layer is thinner. He concluded that their shape creates an optimal boundary layer for greater speeds with less energy.
Explanation from the video: James Gray, an English Zoologist discovered that dolphins managed to attain speeds in the water that exceeded the power limit calculated for their muscles by a factor of seven. This paradox led researchers to investigate what phenomena accounted for this apparent discrepancy between hydrodynamic theory and physical observation. While some have questioned Gray's calculations, others like Jim Rohr at the University of California in San Diego have sought answers to this paradox by studying the fluid dynamics. Using bioluminescent dinoflagellates as visual signals and enhanced video recording equipment, he was able to assess the boundary layer over the dolphins body surface at speeds of 2 m/s. These organisms give off light when the fluid layers around them are subject to stresses %u03C4wall%u22480.1Nm%u22122. He then studied the enhanced recordings and proposed a solution to Gray's paradox. Research revealed that the dinoflagellates failed to light up in regions on the dolphin's body where the boundary layer is thinner. He concluded that their shape creates an optimal boundary layer for greater speeds with less energy.
Biolocomotion, tail walking, and a flipper project
The science studying how dolphins, porpoises, and whales walk on water
Here are two websites where you can take a look at work being done to understand how powerful flukes enable cetaceans (and some fish) to walk on their tails with the bulk of their body above the waterBiolocomotion (tail walking) research at the Dolphin Research Center in the Florida Keys. The image in this post is from the Center, where Rainbow demonstrates his beautiful and powerful tail-walk!
The Flipper Project at West Chester University in Pennsylvania.
Michael Phelps wins medals by swimming like a dolphin
Phelps size 14 feet and floppy ankles function like a dolphin's fluke
A Popular Mechanics article on how Michael Phelps was able to win 8 Gold Olympic Medal concluded with the following observations:
Is Phelps more human, dolphin or submarine?
What makes Phelps's dolphin kick so effective is that, effectively, he swims like a dolphin. Since 2003, Mittal and his George Washington University colleague James Hahn have been analyzing the dolphin kick for USA Swimming, using computer models originally designed to refine the design of small submarines. They found several interesting things. The first is that 90 percent of the propulsion comes from below the ankles. And given that, Phelps's giant, size-14 feet become a huge advantage, functioning almost like flippers.
"Michael Phelps has incredibly flexible ankles, and he can flop his ankles like a dolphin fluke," Mittal says. "Of all the swimmers we've tested, Michael's parameters are closest to that of a dolphin." This preternatural ability to mimic the planet's most efficient swimmer is truly what makes Phelps so good. "The suits do help, and the fact that the pool is deeper and wider has some effect, but why is Phelps so fast?" Mittal asks rhetorically. "It's technique, technique, technique."
Is Phelps more human, dolphin or submarine?
What makes Phelps's dolphin kick so effective is that, effectively, he swims like a dolphin. Since 2003, Mittal and his George Washington University colleague James Hahn have been analyzing the dolphin kick for USA Swimming, using computer models originally designed to refine the design of small submarines. They found several interesting things. The first is that 90 percent of the propulsion comes from below the ankles. And given that, Phelps's giant, size-14 feet become a huge advantage, functioning almost like flippers.
"Michael Phelps has incredibly flexible ankles, and he can flop his ankles like a dolphin fluke," Mittal says. "Of all the swimmers we've tested, Michael's parameters are closest to that of a dolphin." This preternatural ability to mimic the planet's most efficient swimmer is truly what makes Phelps so good. "The suits do help, and the fact that the pool is deeper and wider has some effect, but why is Phelps so fast?" Mittal asks rhetorically. "It's technique, technique, technique."
Michael Phelps on the dolphin kick
A video and an interview
There is a video on YouTube shot underwater showing Phelps do a turn and then swim away using his dolphin kick.A video at SwimNetwork.com (with an ad at the beginning) has a clip of Phelps talking about the dolphin kick and how it came into and changed "the sport."
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