Wednesday, December 10, 2014

How Do Dogs Drink?

There’s more going on than splashing when a dog’s tongue hits the water.
Produced by: David Frank
How Dogs Drink | ScienceTake | The New York Times

Dogs are not just messy drinkers, scientists who have researched the subject say — they are powerful too. They are so strong, in fact, that when a big dog pulls up its tongue after slapping it down on the surface of water, the acceleration can be up to eight times the force of gravity.

Small dogs may exert only four Gs; cats, as they delicately lap their drink of choice, settle for one or two.

For anyone who wonders exactly what kind of science is going on in these studies, the field is fluid dynamics, and the act of lapping up milk or water is an example of a nonlinear interaction between a soft body (the animal’s tongue) and a fluid. So take that, Higgs boson!

To investigate how dogs drink, Sungwhan Jung, Jake Socha and Sean Gart at Virginia Tech and Pavlos Vlachos at Purdue recorded video of 19 dogs of various breeds and sizes lapping up water. They also analyzed video of tubes of different sizes dipping into the water and pulling back, as a dog’s tongue does, to test the importance of surface area.

Dr. Jung was involved in a similar study of cats a few years ago. Neither cats nor dogs can suck in water, as humans can. The reason is simple: Their cheeks don’t close.

Instead, a cat touches the water with its tongue, pulls up a column of water as it retracts the tongue, and bites off a mouthful. Dogs do something similar, except for the force involved. A dog slams its tongue down on the water and pulls it back in with greater acceleration.

The research was presented at the November meeting of the fluid dynamics section of the American Physical Society. So far, Dr. Jung said, there don’t seem to be any practical applications for the research — beyond quenching the thirst of man’s best friend. — The New York Times

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