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Fatality - Northland


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#31 Black Panther

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Posted 15 October 2019 - 09:51 PM

I do remember being taught that the motion dissipates with depth, disappearing at a certain number of wavelengths down
Ill have to dig out an old stage 3 marine physics text.
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  Two figures sat side by side, staring at the Sea. One said to the other, “You know that one day we will die.” And the other friend replied, “But all of the other days WE WILL LIVE!”

 


#32 Black Panther

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Posted 15 October 2019 - 10:04 PM

. Below a depth of half the wavelength (D = 1/2 L), water is unaffected by the wave energy.


From university of Hawaii oceanography dept.
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  Two figures sat side by side, staring at the Sea. One said to the other, “You know that one day we will die.” And the other friend replied, “But all of the other days WE WILL LIVE!”

 


#33 splat

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Posted 15 October 2019 - 11:22 PM

Bp...not sure how that works with my previous example ...serious effects in a submarine at 400ft deep!
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#34 Kestrahl

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Posted 16 October 2019 - 12:58 AM

Bavaria 47? Be interesting to know what happened when it comes out. 


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#35 wheels

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Posted 16 October 2019 - 04:27 AM

A guy I once knew who was on a US Nuclear Sub said that in a severe storm above, they could still significantly feel the wave effects at 600ft down.
BP, maybe you are correct as far as a wave energy is concerned. We all know water cannot be compressed. But there must be some other physical factor involved.
Here's an additional thought to that. The Sea State can be vastly increased in magnitude over a Shoal Bank that may still be considered deep water. I am thinking of the Banks along the East Coast off Gisborn to East Cape region. They are still deep water, but no where near the depth around them. The Sea State over them in a blow can be horrendous. There could perhaps be a tidal flow over them maybe that is not out in the deeper water maybe. I don't know, just a thought


Then 1200ft between crests.
There is no compression only rotation. A particle of water describes a circle as a wave passes. Those circles get smaller with depth. Motion effectively disappears when depth is half wavelength.
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#36 Black Panther

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Posted 16 October 2019 - 06:32 AM

Bp...not sure how that works with my previous example ...serious effects in a submarine at 400ft deep!


Means the wave crests were 800ft apart at the suface.
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  Two figures sat side by side, staring at the Sea. One said to the other, “You know that one day we will die.” And the other friend replied, “But all of the other days WE WILL LIVE!”

 


#37 Black Panther

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Posted 16 October 2019 - 06:44 AM

Check the bottom left graph at 2.49

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  Two figures sat side by side, staring at the Sea. One said to the other, “You know that one day we will die.” And the other friend replied, “But all of the other days WE WILL LIVE!”

 


#38 splat

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Posted 16 October 2019 - 08:43 AM

Thanks BP understood the physics....was struggling to conceptualize the likely wave period and probable amplitude to create such effects
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#39 eruptn

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Posted 16 October 2019 - 11:00 AM

The BOP Regional Council have a wave bouy out off the coast. It records a lot of variables, one is the period. Check it out as the significant period has ranged 3-11sec over the last month, mean period 3-8 sec and height around 3m and a max of 8m etc.

 

http://monitoring.bo...tails?point=822

 

Considering its fixed these are large variations in water behaviour ....... 


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Ross 650 Farr 940


#40 ScarecrowR31

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Posted 16 October 2019 - 05:45 PM

Hi Bp Great clip. Pretty sure though as as waves start to "feel bottom" the orbit slows an they become eliptical and slow down. This changes the wave length,waves closer together and the waves eventually become translatory and break. These eleptical orbits can be felt snorkelling in a swell. you are moved backwards and forwards rather than in a circular orbit. When diving a more an circular orbit.
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