Re: Is there a name for this hydraulic effect, and does it have applications?

Hi Brian,

I'm taking a bit of a stab in the dark on this one. The first thing that came to mind was an article in the May, 2001 issue of Scientific American that discussed supercavitation.

The article, however, is in the context of high-tech torpedos and similar extreme situations. I would be very surprised if a snapping finger would reproduce these. I wonder, however, if under the right conditions, your daughter's and your fingers are able to carry a pocket of air through the water. The moving finger certainly pushes some air ahead of it. At the right angle and speed, the air might form a temporary "cocoon" around the finger as it enters and passes through the water. That might make for very different behaviour than would be expected. The main effect I would think would be to make the impact upon the water much more gradual. It's something that would be very interesting to view in slow motion with a stroboscopic camera.