studied the wet-dog shake

A team of graduate students at the School of Mechanical Engineering of Georgia Institute of Technology, headed by Andrew Dickerson, studied the wet-dog shake.  Bio-inspired design uses the mechanics of nature to understand and create.  It led this group of students to investigate oscillatory shaking -- the wet-dog shake -- to see if it could be applied to make a more efficient washing machine.

With a high speed video camera, they recorded various mammals shaking off water.  What they discovered was: the bigger the mammal, the shorter the shake.  Grizzly bears and large dogs shake at about 4 Hz, or four shakes per second.  Small animals like mice shake at 27 Hz, or 27 shakes per second. X-ray cinematography was also utilized for a look on the inside.

Video recording showed the shake starts at the head and works down to the tail.  The head can twist more, creating a solid starting point for an energy wave to travel the entire length of the animal's body.  But the skin moves faster than the head or body -- think of a whip.  It is integral to how the animal shakes off water.

Centripetal force is a center-seeking net force that is required to keep moving objects in a circular path.  Think satellites.  The wet-dog shake is centripetal force.

Oh, and in case you were wondering, the researchers claim no animals were harmed for this research.  They only had to get them wet.

Will this research lead to better washing machines and other inventions?  Time will tell.

For those curious enough to want to understand the physics of the wet-dog shake, this research will be presented at the 63rd Annual Meeting of the American Physical Society's Division of Fluid Dynamics being held this year at the Long Beach Convention Center in California, November 21 - 23.