The use of air

[JonathanCole]

http://www.newscientisttech.com/arti...zor-light.html
Hull bubbles

Boats could so go faster and use less fuel thanks to nanotechnology research being done for the US Department of Energy by researchers at UT-Battelle in Tennessee, US.
The hull of a boat is first covered with a smooth, tough material such as borosilicate glass. A cutter made of diamond is then used to machine a pattern of grooves and sharp ridges, a few millimetres deep, across the material. Finally, the walls of these grooves are etched with nanometre-sized pits using acid, and then coated with a protective coating of hydrophobic trichlorosilane.
As the patterned hull moves through the water, small bubbles of air become trapped in the nanoscale grooves, providing a low friction cushion, akin to a hovercraft effect. For extra cushioning, pipes from inside the boat can continually feed gas into the grooves. The technique reduces friction on any size craft, and the UT-Battelle team claim it could even help submarines move through the water more efficiently. The researchers report that just a few percent reduction in drag provides a "significant" increase in water speed and fuel efficiency.
Read the full hull bubbles patent application.

[intrepid71]

Originally Posted by ted655

Air is anti displacenent. Safety will suffer. Present day psyics won't allow it. You will have to wait for the goverment to make their antigravity mahine available to the public.

Why is air anti displacement? Water pressure acts in all directions. An air bubble at a given depth will be compressed so that the air pressure within the bubble is the same as in the surrounding water. Buoyancy for a ship is simply the water water pressure acting on the ships bottom, applying a force perpendicular to the surface. If a bubble rests against the ships bottom rather than water it makes no difference because the applied pressure is the same. So the microbubbles will have no impact on the immersion of the ship.

Regarding the "Bermuda Triangle" comments, for an extremely large bubble the envelopes the entire bottom of the ship a different phenomenom could occur. In that instance, once any part of the air bubble reaches the surface, the air pressure in the entire cavity will become atmosheric. This means a sudden drop in pressure at the bottom of the ship as the air cavity essentially collapses. If the "bubble" is big enough the ship could suddenly drop and then find itself swamped as water replaces the collapsed air pocket. This would only be an issue for a truly gigantic bubble.

[kach22i]

Originally Posted by intrepid71

Regarding the "Bermuda Triangle" comments...............

I saw a video or something on TV where they put a toy ship in an aquarium and sunk it using bubbles from the compressor for the fish tank.

Enough small closely spaced bubbles would do the same thing as one large bubble, right?

[jehardiman]

Sighhhhhhh.....

To paraphrase some quotes...

Why don't the bubbles make it sink?

The answer is they do, but it is the amount of bubbles that determine how far it sinks.

Explanation:

Lets say we have water that has a density of 1 kg/l or 1,000 kg per m^3. I then take a “vessel” that is a 1m cube that only masses 750kg (assume it will always have positive GM, which is not a given with an isodense cube) and float it in the water. It will float with a draft of .75m…. right? Ok

Now I begin to blow air in around the hull….For our purposes let us say the bubbles only exist within Xm (say 1m) of the sides of the vessel. This means that the air only affects the surrounding Y volume of water (so 17.25 m^3 for 1m). Now assume I blow enough air in to displace 1% of the water (note: this will be much more than our example 0.1725m^3 because of compression effects, but it is calculable).

What have we done to the draft of our “vessel”?

Assuming the air to be effectively massless, the mass of water has been reduced to 99% of what it was (i.e.17,077 kg =17,250*.99) but the volume filled remains the same (17.25 m^3 for us). Density of the mixed fluid is now 990kg/m^3 and “vessels” draft is now .7575m(i.e. 750/990 =.7575). (Note: this is not exactly true as the increasing draft minutely decreased the volume of the mixed fluid…it is a two variable limit problem which the solution of is left to the student…but you get the idea…).

If we keep increasing the amount of air, the cube will submerge when the mixed fluid density equals 750 kg/m^3. This means that the % air in the fluid is slightly less than 25% of the effected Y volume.

[SamSam]

Originally Posted by intrepid71

Why is air anti displacement? Water pressure acts in all directions. An air bubble at a given depth will be compressed so that the air pressure within the bubble is the same as in the surrounding water. Buoyancy for a ship is simply the water pressure acting on the ships bottom, applying a force perpendicular to the surface. If a bubble rests against the ships bottom rather than water it makes no difference because the applied pressure is the same. So the microbubbles will have no impact on the immersion of the ship.

It's not the pressure of water that floats boats, it's the weight of it that does it. You have a sea of water, and above it, a sea of air. A boat floats on water because it is lighter but its basically sunk to the bottom of the sea of air because it's heavier.
Say a cubic foot of water weighs 62#. Say air weighs 0#. If you have a 1 cubic foot square box (boat) that weighs 31#, it will float with 6" above the water and 6" below. If you mix into the water enough air so its half air and half water, that cubic foot of aireated water will only weigh 31# and so the box/boat would float even with the water, 12" below the surface and nothing above. That's not so bad for a submarine but it's not so good for an open boat. Sam

[StianM]

I can't see that the ship will sink at all.

The air is traped under the boat and would actualy lift it.

If you have a airbubble in your had it will help your hand float.

If you inject large amount off air in the water however it will reduce the densety and the hand will sink.

Air will not reduce resistance acording to some ifo I got on stepped hulls but will increase the efficensy because off reduced wetted surface.

[Verytricky]

Originally Posted by StianM

The air is traped under the boat and would actualy lift it.

I see - special air, that can lift several hundred tons of ship. Why did I not think of that?

[alpamis34]

I reckon this test was carried out for normal conditions such as calm water at 15 degrees celcius.Even though I could not convince my self about how this stuff is going to work at the sea,lets assume that it is going to work when the water is calm.Has anyone ever thought what is gonna happen when the ship sails at a rough sea? This system is going to be totally useless in a wave system.

The second matter is for the ice-breaker ships?How are they planning to push the ice away from the hull surface by those micro bubbles?

[Poida]

Why has nature given fish scales? Maybe as they move through the water tiny bubbles form behind each scale due to the lessening of water pressure, as the back side of a propellor blade does.

These tiny air bubbles could allow the fish to swim through water with less friction.

The airbubbles would not be there to support the ship and yes the pressure on the bubbles would be the same on the bubbles as on the water.

Think of a shaft rolling on ball bearings, the shaft weighs the same, the bearings are there to reduce friction.

Rough seas, so it wont work, does that mean a spinnaker is useless because it can't be used against the wind.

I say give the bubbles a fair go, use helium so the baot will float above the water or nitrous oxide so when the bubbles burst at the surface the crew will all sound like Donald Duck.

[stonebreaker]

Originally Posted by alpamis34

The second matter is for the ice-breaker ships?How are they planning to push the ice away from the hull surface by those micro bubbles?

Ice breakers have been using compressed air for years to push the broken ice away from the boat. It's not experimental - it's been in production for decades.

[Verytricky]

Originally Posted by Poida

Why has nature given fish scales? Maybe as they move through the water tiny bubbles form behind each scale due to the lessening of water pressure, as the back side of a propellor blade does.

These tiny air bubbles could allow the fish to swim through water with less friction.mean a spinnaker is useless because it can't be used against the wind.

Last time I checked, fish sink......

[Poida]

Last time I checked, fish sink......

We are not on the subject of bouyancy we are talking about friction

[StianM]

Originally Posted by Verytricky

I see - special air, that can lift several hundred tons of ship. Why did I not think of that?

Because your from London and the air there is so full of **** that it would sink annything? Weight i not a mather, but weight unit/area unit and none london air won't make the ship sink unless it's injected in the water and decrease the densety to below the densety off the object floating in it.

Originally Posted by Verytricky

Last time I checked, fish sink......

Everytime I checked too. What about birds? there feathers are arenged in the same order as fish shells, but I don't think they fly faster because they trap water behind them

I remeber some years ago Rolls Royce Marine was involved in a project with a special shaped hull and waterjets so it could cross the atlantic in no time with containers riding the waves. The project stalled when it all the suden ocoured to the engineers and hydrodynamics guys that waves not allways from ahead, but from random directions.

Ice breakers use air? I thought they used water to lubricate betwen the ice and the hull.

Atleast that is what discovery chanal told me.

[alpamis34]

We will totally have to deal with friction of course because there is going to be no buoyancy

[kach22i]

You can use a hovercraft or a device which functions like a hovercraft attached to the bow of a conventional ice breaker.

The lift air on the leading water edge pushes the water down. Once the water is removed from supporting the ice above, the cantilever of ice breaks from it's own weight.

I tried to find a diagram but could not on short notice - have to picture it yourself.