vox_mundi wrote:Tanada wrote:vox_mundi wrote:Tanada wrote:I don't get why the reporters took this news and ran off to proclaim it solves the Bermuda Triangle question. The Barents Sea is thousands of miles from Bermuda! On top of that a rising gas column causes all the water to churn upward making ships and boats rise higher, not sink!
Actually, this is old news that circulated about ten years ago. A blowout of a large pingo in the North Sea sunk a large fishing trawler which was discovered 400 ft down sitting upright in the center of the resulting crater.
When a large plume of methane blows out, the resulting bubbles reduce the density of the water column. If the boat exceeds this density, it drops like an elevator.
Relative density. It's why an ice cube floats on water and sinks on gasoline.
Yeah that was the theory, however when they tested it by releasing large quantities of pressurized air under boats it was demonstrated that the theory does not work in real life, ...
Do you have a link to this study?
Thought experiment:
Take a cubic meter of water (density = 1,000 kg/m³)
Replace half the volume with methane (density = 0.656 kg/m³)
Then each cubic meter of the mixture has a density of 500.3 kg/m³
Say this change in density occurs over a quarter mile of sea surface
If a ship normally displaces 100,000 cubic meters in water the ship would have to displace twice the volume (200,000 cubic meters) to remain afloat. If water over tops it will become an instant submarine.
Will it float? Maybe empty; but full, I don't think so.
Except you are not changing the static density of the water, what you are doing is bubbling gas through the water. Sure if you take an instantaneous average of the density of the water column you can say the value is reduced by 50 percent, like you did.
However in the real world the column is not just sitting there at 50 percent the average of the water all around it. First off you start with a burst of gas deep below the surface, all releasing in the space of a few seconds to just a few minutes at the most. We know this based on the shape of the Pingo craters we find on the sea floor, if the gas were released slowly the crater would have a different appearance. So here you are releasing this burst of gas 400 feet (130 meters) below the surface. What happens next? Well the gas is much less dense than the water above it so it starts rising very rapidly to the surface. As it rises the turbulence of passing through the water breaks it into smaller bubbles, and it spreads out somewhat horizontally as well.
Then what? Well as the gas rises it has several effects on the water, namely it pushes the water horizontally out of its path. Then as it passes any given spot is causes the water that was pushed aside horizontally to be sucked back in to replace the volume of the gas that has passed through that spot. This is compounded as the gas continues to rise creating a slight partial vacuum underneath the bubbles. Just like what happens to the air when a large truck travels at high speed, the column as a whole is driven in the same direction as the passing gas bubbles. What you end up with is a wide spot on the surface where the gas bursts out followed by the up welling of the water column that was put in motion by the wake of the gas bubbles as they were drawn along in the turbulence.
At no time is the whole water column of a static 50 percent density. In point of fact only the zone moving up the column where the mass of the bubbles are located at any instant in time has low density. If the gas is all released in one explosive burst that probably lasts less than 2 seconds and it takes 30 seconds to ascend all the way to the surface then when the burst reaches the top of the water the low density zone is only 26 feet thick. Now put that directly under your hypothetical tanker, what happens? Worst case scenario your "drops like an elevator effect" drops the ship 26 feet to the top of the nearly gas free portion of the water column that is itself rising upward like an elevator. However in the actual situation that mixed water/gas burst breaking through the surface has a lot of water mixed in it, and that water is hitting the bottom of the hull and pushing it up despite the low average density of the gas burst water mixture. Then as the gas/water mixture finishes passing up around the hull of the ship the fast moving water column that was drawn up by the passing gas arrives and runs into the bottom of the hull also pushing it up.
Net effect, a column of gas and spray shoots up all around the ship, the deck gets wet and the ship gets jolted as the water refills the space left behind by the gas.
Video proof the theory does not work in practice.
https://youtu.be/Ux9sogZkIm8