Friday, December 19, 2008

Water Really is Evil

Dead water it's called. Ship captains have known that the water in which they sail can cause their ship to spontaneously slow. Triathletes and strong swimmers have often complained the sea water is 'evil' sometimes because they lose momentum and they tire quickly. It's suspected this evil water has caused drownings.

Scientists may now know what causes the evil dead water. Leo Maas, a fluid dynamicist at the Royal Netherlands Institute for Sea Research, said,


"We've been considering the possibility that the drownings of strong swimmers in fair-weather conditions might be the result of dead water, but until now, we weren't really sure if this phenomenon could strike something as small as a single human. Now it seems that it can."
New Scientist has the full story.



The life of Indigo Red is full of adventure. Tune in next time for the Further Adventures of Indigo Red.

3 comments:

Anonymous said...

I have hard time "fathoming" how a swimmer's passing coulod trigger enough of a wave to cause this phenomenom. Don

Indigo Red said...

Nice pun, Don!

It's not necessary to create a large wave. The wave only needs to be in proportion to the moving body. Remember that Archimedes discovered in the bath that his body weight displaced an equal volume of water.

In the evil water phenomenon the surface water does not need to be very deep, but the water density between the two layers of water do need to be signicant enough that the swimmer contacts the denser water below. The density is the cause of the slowing. The wave generated, even a very small wave, that advances before the body introduces dense water into the swimmers path and stroke, thus slowing forward motion.

Most triatheletes are fairly lean individuals without much of the body fat that would keep most of us near the surface. The lean, dense body mass of the swimmers would cause them to sink like a stone in still, or 'dead', water.

Think of it as 'black ice' on a road. A very small patch of thin ice can send a very large vehicle spinning out of control. Dead water absorbs forward motion causing the body to be dead weight spinning out of control beneath the surface.

Indigo Rose said...

This is a better explanation as to why I always lost at swim meets. I would hate to think I really was that slow because of my technique!