Naked Science Forum

Non Life Sciences => Physics, Astronomy & Cosmology => Topic started by: Aquila on 22/01/2008 17:41:44

Title: Water waves
Post by: Aquila on 22/01/2008 17:41:44

Why does the speed of shallow water waves decrease as the water depth decreases?

Title: Water waves
Post by: JimBob on 22/01/2008 21:59:47

It doesn't. Speed increases.

Title: Water waves
Post by: lyner on 23/01/2008 22:12:07

Correct. That's why waves break when they come ashore.They are going too fast for the water depth and fall over themselves.

Title: Water waves
Post by: JimBob on 23/01/2008 22:36:34

Ah, an oceanographer in the making answering the question! BRAVO!

Title: Water waves
Post by: daveshorts on 24/01/2008 10:52:55

According to this:
http://www.seafriends.org.nz/oceano/waves.htm

The speed of a wave in shallow water (where the depth is less than the wavelength) is proportional  to the square root of the depth of the water.

In a wave the water particles move in little circles or ovals, in shallow water for the same wave height the particles have to move further, so the effective inertia of the system is higher so the wave speed is lower.

[diagram=311_0]

In the deep water more water can move less far to produce the same effect, this takes less time so the wave moves faster.

Title: Water waves
Post by: lyner on 24/01/2008 18:04:46

Quote from: JimBob on 23/01/2008 22:36:34

Ah, an oceanographer in the making answering the question! BRAVO!

A little anthropomorphism never did anyone any harm!