A twist of a knob sets water jets in motion, causing water in this giant cylindrical tank to spin. Soon, a tiny vortex appears at the surface, gradually swelling in size as it snakes downward.
The pattern you see here is called a vortex, found in rapidly rotating fluids. Funnel-shaped forms such as this occur in both liquids and gases. You make a vortex every time you stir your coffee, flush a toilet, or empty your bathtub. Tornadoes, waterspouts, and dust devils are also vortices.
Look closely and you may notice a corkscrew-shaped pattern on the surface of the spiraling water. This pattern is a profile view of surface waves that have formed on the inside of the vortex. Although the waves appear to be stationary, they are actually traveling up the downward-moving water. The effect is the same as a person walking up a down escalator.