About That Wet Dog...

Scientists Reveal How Fast Dogs Must Shake To Dry Their Fur

(from NPR.org)
If you've ever seen a dog trying to shake itself dry after taking a plunge into water — or perhaps while standing next to the person who just gave it a bath — you've probably noticed that the technique can throw off a shocking amount of water.

That's all part of nature's design, says Andrew Dickerson, a graduate student at Georgia Tech. Talking with NPR's Robert Siegel, Dickerson described his recent study of how fast different animals "oscillate their bodies to shed water droplets," as an abstract of his work states.

If that's too esoteric for you, check out this video:



For his study called "The Wet-Dog Shake," which appeared in the journal Fluid Dynamics, Dickerson and his colleagues slowed down images of animals — dogs, a bear, even a mouse — shaking themselves dry. The footage was shot with a high-speed video camera.

The researchers found that both bears and dogs shake at a similar speed — around 4 Hz and 4-5 Hz, respectively. In this case, hertz refers to the frequency of skin oscillations per second. And it turns out that the smaller the animal, the faster it has to shake to dry. Thus, a cat can get by with shaking around 6 Hz. But its nemesis, the mouse, requires 27 Hz to dry off.

Dickerson says that his work focuses on discovering mechanisms found in nature. The research on how animals shake off water, he says, may have real-world applications in improving the design of washing machines.

But he does not recommend that any human try to duplicate what is, by many rights, a dog's trick.

"If you were to get down on all fours and try to shake off water after a shower," Dickerson says, "your efforts would be most unfruitful."