Gray’s 72-yr old Paradox solved, dolphins really are that powerful

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Gray's 72-yr old Paradox solved, dolphins really are that powerful

Troy (NY) – Researchers at Rensselaer Polytechnic Institute (RPI) have finally put to rest the 1936 claim by British zoologist Sir James Gray. Gray studied dolphins and concluded that their muscle strength was insufficient to propel them at the 20mph speeds they were seen swimming in the ocean. Gray believed some unique surface interaction was taking place which reduced drag. However, RPI scientists have now modeled the dolphin and claim their muscles really are that strong.

The research team was led by Timothy Wei, professor and acting dean of Rensselaer’s School of Engineering. Wei presented his findings at the 61st Annual Meeting of the Physical Society (APS) division of Fluid Dynamics in San Antonio, Texas.

Wei collaborated on the project with Frank Fish, a biologist at West Chester University in Pennsylvania; Terrie Williams, a marine biologist at the University of California, Santa Cruz; Rensselaer undergraduate student Yae Eun Moon; and Rensselaer graduate student Erica Sherman.

No special drag

Using a new state-of-the-art water flow diagnostic algorithm, and modifying and combining force measurement tools developed for aerospace research (which use a 1000fps camera to study digital particle image velocimetry), Wei applied the algorithms to determine where the muscle thrust was being delivered. He videotaped dolphins swimming with tiny air bubbles in the tank. The computer tracked the bubble movement and Wei applied them to the fluid algorithms for measurement.

The result was a model showing that the muscles do produce that much force, as much as 300 to 400 pounds of force. Compare that to an Olympic swimmer that produces a maximum of 60 to 70 pounds of force. In addition, Wei measured dolphins doing their famous “walk on their tail” trick in water. He concluded that during that impressive display the dolphins are producing on average 200 lbs of force.

Read more at Rensselaer Polytechnic Institute, and watch a video showing computer tracking of the dolphin’s motion through the bubbly water.