One of the world's great questions has finally been answered by Georgia Tech researchers: Why do dogs shake when they're wet?
Their article, titled "The Wet-dog Shake," was published in the journal Fluid Dynamics. The nature of such demonstrations was investigated by a fluid mechanics physicist and his learned colleagues.
They first filmed a Labrador retriever, then a number of other dogs, as well as other mammals, as they shook dry. It's an important process, especially for wild animals, because the ability to dry wet fur or hair is critical to temperature regulation.
Using the films to measure periods of oscillation (how fast the animal rotates its body) to dry its fur, they discovered that, for a Labrador retriever, it was 4.3 hertz (cycles per second).
The physicists also determined that the centripetal force necessary to eject water has to exceed surface tension. They found that the smaller the animal, the more times per second they must oscillate to dry. A mouse, for example, shakes at 27 hertz and a bear at 4 hertz. These scientific findings were described in the journal Fluid Dynamics.
The study was far more detailed than we have described, but you get the idea. Dogs use the centripetal force of shaking to expel water from their hair in order to regulate their core body temperature.
So, when your dog soaks you from the waist down, there is hard science behind the act. It's nature, not a decision he makes to aggravate you!
