This is a pretty simple experiment to create nifty interior fountains — although maybe not as cool as the ones in this video. Take a container, like a wine glass or a bowl, hold it upside down, lower it into liquid, and jiggle it around. Voila! Instant fountain.

The fluid in this video is silicone oil, not water, so you’ll get different results trying this at home. But the physical principle should be the same. Push the vessel of choice up and down, and the “triple line” — the line at which the oil, air, and solid meet — goes up and down with it. At first the results aren’t impressive, but eventually the motion hits a critical level. As this 2010 paper describing the dynamics notes:

Above a given acceleration that depends on the immersion depth and on the shape vessel, wave goes under the corner edge of the bell. During the oscillation, the wave generates at the edges presents a singularity that leads eventually to a jet and a drop ejection. A drop is ejected at each oscillation.

Once the the oscillations get fast enough, the motion stops just creating waves and starts flinging droplets in the air, making a fountain.

How well can you duplicate the effect with a clear wine glass at home? All you need is a wine glass and a lot of liquid to dip it into. The next time you’re getting drunk in the tub, considering giving this experiment a try.


[Source: A fountain of droplets]