Floating Breakwater Design

[flash3780Subscriber]

Hey folks. I’m wondering if anyone has any good references for ocean wave mechanics and floating breakwater designs. I proposed a deepwater harbor for refueling merchant traffic over in the Business Model section, but the feasibility hinges on constructing effective breakwaters.

I started working out the mechanics of breakwaters, but as it turns out, it’s a pretty complex fluid-structure interaction problem that’s beyond the scope of any mechanics references that I own. My first instinct is to build a simple CFD to see the effect of a large wave slamming into a large floating mass… however, that’s probably not the best place to start. I did some digging and found this text on wave mechanics, but before I make an investment, perhaps folks on here have some advice on good ocean engineering references (I work in aerospace, so I usually solve different types of problems).

The trick in designing an open-ocean floating platform seemingly involves both significantly attenuating large waves (~5m amplitude), and ensuring that the platform survives extremely large waves (~20m amplitude) with non-catastrophic damage (i.e. staying afloat). I have a feeling that the latter is the more difficult challenge.

The Draupner wave in the North Sea which occured on New Years Day, 1995 is an example of an event that must be survived, though damage to the platform might be expected.
Draupner wave

Clearly, this is a challenging design. However, I wonder if it would be more effective to have a single, larger floating breakwater, or to have multiple layers of protection.

Also, I wonder if anyone has information about what sort of you see in the wavelength of real-world ocean waves. Here is some information that I’ve been able to dig up thus far on winds and wave amplitudes:

Wind energy:
Wind energy map

Wave heights:
Atlantic Ocean
World Map

That said, larger wave periods are very problematic.

I have a feeling that this is a problem that’s already been solved somewhere… does anyone have any good examples of existing deepwater floating breakwaters?

Thanks for the help.

[flash3780Subscriber]

I found this Army study on floating breakwaters. There seems to be some good information in there.

Floating Breakwater Prototype Test Program: Summary of Data Analysis Efforts

Let me know if you guys have any good information on breakwater design. After some thought… I’m thinking that a wider breakwater would be more effective at eliminating large amplitude, low frequency ocean waves.

[YaroslavSubscriber]

Hi everyone, happy to discover such a like-minded!

flash3780′s, my point of view agree with your idea for deepwater harbours, not only as a refueling place, but as a city basis.
I think there is no need to build huge vessels, cheaper and more liberal to provide such a harbour, which will be filled with personal boats.
Maybe even somebody will build concrete floating houses in the floating docks using imported cement.

Main task is wave breaking. Why waving is so destructive? Because it accumulate energy for some time/distance,
and regular wave-breaking releases this energy in a moment.
Why not try to reduce this energy in the same manner as it appears?
Waving energy consists of 2 components:

1.Transverse surface waves. This part could be reduced trough the surface affecting, for example by covering it with foamed rubber, which also could produce energy.
2. Horizontal current caused by wind. This current come into turbulent state on the top of the wave, and will damage such a rubber covering. Therefore, this component should be reduced first.

Whatever it will be, algae forest, 3d-rope-network, anything else, it should generate artificial viscosity.

The most crazy idea is to use foam viscosity: Produce at depths permanent micro-bubbles flow, while in depth, under pressure, them will occupy not much space for significant merging. On surfacing, those bubbles will get bigger, producing significant viscosity. The same effect could be observed when huge wave breaking shore, followed by foamed and therefore unusually calm water.

It’s all just imagination, no calculations made yet.

[YaroslavSubscriber]

Unfortunately deeper analyses revealed bubble idea failure: high pressure leads to increased air solubility, which at first, will consume pumped air, then, while drifting up, saturated water will become oversaturated and will significantly increase passing bubbles, which in turn will lead for increased speed and therefore too much air consumption

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