New Ship Will Remain Stable By Creating Its Own Inner Waves

Zothecula writes "When offshore oil drilling rigs are being installed, serviced or dismantled, the workers typically stay in cabins located on adjacent floating platforms. These semi-submersible platforms are towed into place (or travel under their own power) and then their hulls are partially filled with water, allowing them to remain somewhat stable in the pitching seas. Now, a ship is being built to serve the same purpose, but that will be a much more mobile alternative. It will keep from rolling with the waves by generating its own waves, inside its hull."

Comments

It's about time

[Anonymous Coward]

I used to do that in my bathtub. It's nice to see someone finally upscaled it like this.

Power requirements?

[danceswithtrees]

The system pushes water from side to side using compressed air to counteract rolling from ocean waves. Granted this is for use in drilling rigs (read big money), but I wonder how much power is required to run the air compressors. The compressors have to be high flow to rapidly move a lot of water, albeit at relatively low pressures-- only 4.4 psi required to generate 10ft difference in seawater (this does not take into account viscosity and inertia).

Re:Power requirements?

[danceswithtrees]

That is a different problem and not a fair comparison. The wave in an aquarium is being stimulated at the natural resonant frequency. If you slosh the water in a tank without the wave device, it will go back and forth at its natural frequency losing a little bit of energy with each slosh. In much the same way that you can maintain the swinging of a heavy pendulum with very little energy, the wave thingy you reference is energizing the wave at the natural frequency of the tank. If you were to try to make waves at 70% or 124% of the natural frequency, I think it would take MUCH more energy.

You can't reasonably expect the ocean to rock the boat at the resonant frequency of the internal water tanks. Therefore the ship's internal wave system is going be expending a considerable amount of energy. Ships weigh tons. To counteract the rolling motion of a several ton ship, you are going to have to move several tons of water several times per minute.

Mercury Pots

[Lev13than]

Reminds me of the chapter in Neal Stephenson's The Confusion (part of The Baroque Cycle). Japanese mercury vendors try to disable the Minerva (an armed merchant vessel) by filling its cargo hold with half-filled pots of mercury, rather than filling them to the brim. The idea is that the sloshing in the hull would resonate with the waves at the entrance to the harbour and slow the ship enough to be captured (or something to that effect). There's a discussion of whether Stephenson got the science correct here.

Re:Need that for my water bed

[gsgriffin]

I'm glad you clarified 'folds' as being a part of your bed and not you.

SWATH doesn't require power

[CanadianRealist]

Small Waterplane Area Twin Hull (SWATH) is a design that minimizes the effect of the waves. Most of the volume that supports the ship is below the level of the waves, making it very stable. The stability comes from the hull design, so it doesn't require any power and the stabilization isn't prone to failure like an active system.

Here's a short video of a SWATH ship in rough seas, with a regular hull ship for comparison. I'm pretty sure this is the one that I saw in a documentary about the design. They showed a glass of water sitting on a table in the SWATH ship, not spilling. I'm pretty sure that the glass would go flying in the other ship.