Tuesday, July 21, 2009

How a Raindrop Is Like an Exploding Parachute

This has a very high cool factor, even if you only look at the high-speed video.

A bunch of physicists have look at how raindrops can behave almost like an exploding parachute as it falls through air.

The idea has been that raindrops grow as they gently bump into each other and coalesce. Meanwhile, more forceful collisions break other drops apart into a scattering of smaller droplets. All this action would explain the wide distribution of shapes and sizes. But trying to unravel how the drops crash and break up led to a tough set of equations.

The new movies, however, show a much more straightforward process. Researchers snapped 1000 pictures a second of an isolated water drop as it fell through an ascending air stream. The drop first flattens into a pancake shape, which then balloons like a parachute. The bottommost rim of this chute has a thick, irregularly corrugated rim. Pressure from the air drag eventually breaks the chute apart into numerous smaller droplets--their wide range of sizes is due to the wide range of sizes of the bumps in the rim.

While there are certainly valid reasons why important and significant research should get a lot of publicity, I still like these kinds of small and "cute" studies, simply out of curiosity for my part.


1 comment:

Michael F. Martin said...

There are always practical implications to be drawn from the study of nature.

How about this lesson from that video: large-scale, low-frequency effects (air drag) can dominate short-scale, higher-frequency dynamics (surface tension/adhesion)?

People are generally not curious enough about nature.