From: SFPhysics@aol.com
Date: Sun Jul 16 2000 - 01:54:24 PDT
From: SFPhysics@aol.com Message-ID: <4e.85795f1.26a2d240@aol.com> Date: Sun, 16 Jul 2000 04:54:24 EDT Subject: Re: water waves
OPPS, SORRY! This was sitting in my outgoing file and never sent. I hope
the material is still timely.
> Subject: Water waves
> From: "Joe Stewart" <jstewart@marin.k12.ca.us>
> Date: Mon, 10 Jul 2000 11:36:13 -0700
> What I know:
> Wave speed depends on frequency and wavelength. Sound and light always
> travel at the same respective speeds in a given medium. Surface water
> waves vary in speed and are, like sound and light, dependent on wavelength
> and frequency (period).
> What I want to know:
> Is there also a direct relationship between the size (amplitude/ height) of
> a water wave and its speed?
>------------
> J. Stewart
> jstewart@marin.k12.ca.us
>>
Waves on the water have determinants that you would not normally encounter.
Since the waves are really disturbances between two dissimilar media, much of
the action is determined by the value of g (9.81m/s^2). Gravity is the
spring or restorative force and the water is the mass or inertial component.
The usual driving force is friction between the two media caused by wind.
Wind driven waves can never go faster than the wind across the water. One
must also note that waves in the water side of the media pairing are really
particles traveling in a circle (deep water mode). Wind waves have periods
ranging from 3 to 30 seconds, tidal motion considered as a wave has a period
of 12 hours, and seismic sea waves are in between these and vary in distance
from the source point. Wind waves in the area they are being generated are
forced waves and do not follow any perfect formulas.
I am assuming you are interested in wind whipped waves emerging from forced
wave areas so here goes. Wind waves are very much dependent on Lord
Rayleigh's probability distribution tables. i.e.: Wind is somewhat random
so waves will be too. When wave trains do form and are caused to increase in
intensity by more wind action, a single periodic component of the interface
between the two media spectral response in deep ocean will be where wave
length L and a wave celerity C (velocity of transmission), become directly
related to the period T when the waves are left to themselves and are no
longer being forced. Then and only then do we get to the formula for Wave
Velocity = square root of (g x Lambda / 2 pi). Now my interpretation is
that the amplitude is not a factor in this interaction between the boundary
layer of two viscous fluids (water & air).
The tsunami is v = square root of (g times ocean depth). So the square root
of 9.81 m/s^2 times 1000 meters gives a wave velocity of 99 m/s as an example.
Al Sefl
p.s.: I hope this helps.......
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