Re: [Paddlewise] Surfing Deep Water Waves [was: Stability]

Matt Broze wrote:

> John Winters wrote:
> <SNIP>

> > Breaking waves present a different problem and one has to work to avoid
> > being swept ahead at the translational speed of the breaking wave crest
> > which exceeds twice the wave speed (or, if into these things, work to
> > maintain an ideal position on the breaking wave face.
> 
> I may be missing something here, but I fail to see how the transitional wave
> (breaking soup) can travel faster than the deep water wave crest that
> created it.

Matt, I think Winters is referring to the *breaking* wave crest, **as** the
wave turns into a breaker, and you are referring to the resulting transational
wave ("the soup") -- he is talking apples and you are speaking oranges.  The
top of the breaking crest moves forward (momentarily) faster than the lower
part of the wave -- a feature which disintegrates quickly to form soup.  In any
case, I wonder how well-developed good theories are for soup, it being a rather
disturbed, turbulent state (re:  formula you quote below).

> Or even much faster than the speed of the slowed and steepened
> breaker that created it moments before. Just how and why does it suddenly
> pick up any extra speed much less "exceed twice the wave speed" as John
> says. I have a found a formula that calculates the speed of a translational
> wave (soup) that is based on the waves height and the depth of the water
> below it. (speed in ft/sec. = sqrt (wave height + water depth) x 32)
> (multiply the result by .59155 for speed in knots). While this may make it
> appear that speed is independent of the parent wave's speed and size, it is
> obvious that the size of the initial wave is going to determine how high a
> soup can be. The speed (depends on wavelength) and the wave height of the
> parent wave will determine into how deep of water the wave breaks. I'm not
> sure yet how the soup's height relates to the height of the deep water wave
> (or the height of the breaking crest) but from my experiences surfing I'd
> say that the transitional wave height is far smaller than the breaking crest
> height (I'd guess about 1/2 as high as the breaking crest--couldn't find
> this info in "Waves and Beaches"). Since a wave breaks in water about 1.3
> times its wave height and a deep water wave won't get any higher than
> 7 times its wavelength

Matt:  you mean ** 1/7th ** its wavelength, don't you?

> without breaking this will put an upper limit on the
> heights and water depths to plug into the formula above. 

-- 
Dave Kruger
Astoria, OR
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