More than 70 years later, Wei has developed a tool that conclusively measures the force a dolphin generates with its tail.
Wei created this new state-of-the-art water flow diagnostic technology by modifying and combining force measurement tools developed for aerospace research with a video-based flow measurement technique known as Digital Particle Image Velocimetry, which can capture up to 1,000 video frames per second.
Wei videotaped two bottlenose dolphins, Primo and Puka, as they swam through a section of water populated with hundreds of thousands of tiny air bubbles. He then used sophisticated computer software to track the movement of the bubbles. The color-coded results show the speed and in what direction the water is flowing around and behind the dolphin, which allowed researchers to calculate precisely how mush force the dolphin was producing.
See a DPIV video of Primo here: http://www.rpi.edu/news/video/wei/dolphin.html
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 comp
|Contact: Michael Mullaney|
Rensselaer Polytechnic Institute