The Dive Bell effect?

[Olblindman]

The more recent theories suggest that the stern did not raise up as high as previously thought before the ship ripped in half. That would allow water to rush in more uniformly, reducing the chance of air pockets, although certainly they were created. I doubt if anyone would have survived too long, either way. I doubt they would have made 70 seconds....

 

[TimTurner]

Arun asked me a year ago, and I've just opened my messages now. I've done the rough math, so I figure the community should benefit from it:

Mr Turner, I want to ask how much this effect would have affected any people trapped and alive in the stern section of the Titanic. There is a chance that a few of them would have been trapped in relatively small compartments at the extreme stern well within the bowels of the ship. In that case, those areas would have taken longest to flood and some air pockets probably still remained until the stern imploded at about 500 feet depth. Also, if there were no large loose objects there, the persons might have remained relatively uninjured and conscious.

If you hypothesise this scenario, what would be the air temperature gradient in those 70 seconds (I think you said elsewhere) that it took the stern to reach 500 feet?

Sorry, I have been gone for some time. - nearly a year.

If you are still interested, here is my answer:
The water pressure increase would have increased as the depth increased. This would have been nearly instantaneous (within probably 10 or 15 seconds, but hard to say). The water would have, in turn, pressurized the air. This would have been even more nearly instantaneous (a second or less). So the pressure of the air in the Titanic would have been almost the same as the water around it.

So the speed of pressure increase would have been the speed the Titanic sank. Seawater pressure is 1/2 pound of pressure per square inch every foot, as a general thumb rule (14.5 psi every 33 feet to be more exact). At 33 feet, the pressure is 14.5psi, at 100 feet it is 43.5 psi. (14.7 psi is the pressure humans are accustomed to from the weight of Earth's atmosphere, and we call this pressure "1 atmosphere" of pressure.)

We don't know for certain, but as general knowledge, the Titanic sank at about 30 mph and took about 5 or 6 minutes to reach the bottom. The Titanic is 12500 feet down, which means that it descended at about 2500 feet per minute, or 41.6 feet per second. That means the air pressure would have increased proportionally (41.6 divided by half) which gives us about 20.8 pounds per second.

We also need to remember that the Titanic didn’t fall at an even speed. It would have started slowly, picking up speed, until it hit Terminal Velocity of about 30mph in sea water (if you remember from High School physics, this is the speed at which the force of friction will equal the force of weight of the object, so downward acceleration stops. Friction is greater in water than air, so terminal velocity is much lower for a sinking ship than a falling airplane).

https://en.wikipedia.org/wiki/Gas_compressor#Temperature

Using the formula:
T2 = T1 (P2 / P1) ^((k-1)/k)
We can calculate the temperature. We must also use absolute temperature and pressure, so what we consider normal air pressure is actually 14.7 psi, and we must add the weight of this air to all our water figures, too (because the atmosphere is pressing down on the ocean water). We also will need absolute temperature. I’ll use Rankine degrees, because the math is simpler conversion to Fahrenheit (just add about 460).

K is a constant, which is about 1.4 for air.

If we assume the air temperature below decks on Titanic was 50 Fahrenheit degrees (+460 = 510 Rankine degrees), and 14.7 psi at the surface. At 500 feet (reached in about 12 seconds) pressure would have been about 220 psi (plus 14.7 atmosphere). We can calculate:

T2 = T1 * (P2 / P1) ^((k-1)/k)

T2 = 510 * (234.7 / 14.7) ^((1.4-1)/1.4)

T2 = 510 * (15.96) ^(.2857)
The 15.96 is our compression ratio. A typical diesel engine has a compression ratio of about 14-22 (source wikipedia).

T2 = 510 * 2.2

T2 = 1125 Rankine degrees

-460 to convert back to Farenheit

Gives us 665 Farenheit degrees final temperature (351 C). That’s a 615 F increase over 50 F (10 C). This would have happened in about 12 seconds so, 51 F per second (28 C per second). Or using the original 70 seconds, 9 F per second (5 C per second)

Granted , this is rough math. We don’t know the interior temperature of the Titanic before the sinking, but we can assume it was mostly around 50-60 F degrees. 70 F is normal room temperature. Exterior temperature was recorded as 48 F degrees, and we know they were turning heaters on because they felt cold, in 1st class and the bridge so we can assume that 3rd class probably wasn’t too much warmer than outside air (at least, somewhere between 48 F and 70 F).

We must also remember that the seawater was near or below freezing. This would have sucked heat out of the Titanic, like putting a boiling hot pot in the freezer. It won’t stay hot for long.

Finally, the Titanic started sinking slowly, then picked up speed. It probably took a bit longer than 12 seconds to reach 500 feet. Probably closer to 30 seconds or a minute. It’s maximum speed was about 30 mph. If it was 70 seconds, that would be a bit less than 9 F per second (5 C per second).

Which means it was a very hot ride down, and if you hadn't already passed out from the pressure and heat, you were probably grateful when the ship imploded in the crushing embrace of freezing waters.

Yes, morbid, I know, but something a submarine sailor thinks about.

 

[Christophe Puttemans]

I'm still trying to imagine what would happen to somebody trapped in the giant air pocket when the stern broke free from the bow and started to sink. Let's place this person in the First Class Smoking Room, and assume that room was torn apart at the first big implosion which caused the stern's pitch to level off. Would he still be alive by then, conscious and wondering what the hell was happening, or would extreme heat and pressure have killed him already?

 

[TimTurner]

I doubt the 1st Class smoking room would not have formed much of an air pocket, the large glass windows would have burst, and doors would have let the air out very quickly. When I think of air pockets, I usually think of 3rd class berthing down on F and G decks, perhaps some of the food storage spaces.

I don't know that anyone has studied the question deeply. You'd want a doctor to fully answer that. I don't know about the pressure - hopefully it would knock you out. But rapid pressure would probably damage your ears, lungs, and eyes, and be extremely uncomfortable to very painful. That would probably be overshadowed though, because the temperature would be hotter than an oven, and at some point the floors and woodwork (possibly your clothes) might catch on fire.

I would guess most people would be in pain for 30 or 40 seconds before passing out, and some people might have been alive for a full minute or two before the stern exploded and everyone died, but I certainly don't know.

 

[Christophe Puttemans]

Thanks, I know enough for now on that topic.

 

[Arun Vajpey]

I would have thought that air pockets were only likely in the extreme stern, in deep, centrally located areas which had no portholes or even a 'hull wall'. In such areas, might it have taken close to a minute for the flooding water to burst through? Therefore, if someone was still alive in such spaces, might they have remained conscious for those 40 or 50 seconds? It can feel like a VERY long time to a suffering person.

 

[Arun Vajpey]

I was looking at BB's deck plans on this site and zeroed on Third Class accommodations on F-deck to try and explain what I had in mind. Take Cabin F-180 for example; it is well into the stern and located centrally and so would have had no portholes. It would have remained dry till very late....the question is how late?

I do not know if it was allocated to anyone but assuming for a moment that it was and that someone was unable to get into any lifeboat and had returned to the cabin in despair to wait out for the end. By its location, it might have taken a while, maybe even 2 or 3 minutes, for it to flood after the ship hand broken up because the water had to traverse several bulkheads and other obstructions on the way. As the stern rose again and sank, F-180 could have had air pockets trapped in there. The tiny size of those cabins with few amenities would mean that there were not many things nor much space for objects to fly around. Therefore, it is conceivable that someone in F-180 could remain alive for a minute or more after the break-up.

 

[Augusto Félix Solari]

I'm still trying to imagine what would happen to somebody trapped in the giant air pocket when the stern broke free from the bow and started to sink. Let's place this person in the First Class Smoking Room, and assume that room was torn apart at the first big implosion which caused the stern's pitch to level off. Would he still be alive by then, conscious and wondering what the hell was happening, or would extreme heat and pressure have killed him already?

Besides, the Smoking Room would have been seriously damaged as a result of the break up... not only with the large windows breaking but with the columns collapsing and probably the fourth funnel falling on top... not a good place for an air pocket,

 

[Scott Mills]

I doubt the 1st Class smoking room would not have formed much of an air pocket, the large glass windows would have burst, and doors would have let the air out very quickly. When I think of air pockets, I usually think of 3rd class berthing down on F and G decks, perhaps some of the food storage spaces.

I don't know that anyone has studied the question deeply. You'd want a doctor to fully answer that. I don't know about the pressure - hopefully it would knock you out. But rapid pressure would probably damage your ears, lungs, and eyes, and be extremely uncomfortable to very painful. That would probably be overshadowed though, because the temperature would be hotter than an oven, and at some point the floors and woodwork (possibly your clothes) might catch on fire.

I would guess most people would be in pain for 30 or 40 seconds before passing out, and some people might have been alive for a full minute or two before the stern exploded and everyone died, but I certainly don't know.

Tim,

Revisiting this after years! In any case, as we know both Oxygen and Nitrogen, when compressed become highly toxic. My inclination, without doing the requisite calculations, is that any person "trapped" on the sinking Titanic would be rendered unconscious from the combined effects of Oxygen and Nitrogen toxicity well before they burst into flames; however, not quickly enough to not suffer from some of the equalization effects (like bursting eardrums).

 

[Arun Vajpey]

I think that gas compression would have taken several minutes and by that time anyone on board anywhere would surely be dead. But I am trying to picture the last minute or two of a Jane Doe trapped in one of those deeper stern cabins after the Titanic broke-up. In pitch darkness with all sorts of horrible sounds around her, being tossed around and probably being able to "sense" the water approaching. Even if it took only 80 or 90 seconds, it would seem very long to someone in Jane Doe's position.

 

[Christophe Puttemans]

Besides, the Smoking Room would have been seriously damaged as a result of the break up... not only with the large windows breaking but with the columns collapsing and probably the fourth funnel falling on top... not a good place for an air pocket,

Thanks for this, it's good to know. In my book, I have Chief Officer Wilde looking for Thomas Andrews. A fictional character says he is in the smoke room, but when Wilde arrives there, the room is empty. Before Wilde can leave again, the Big Wave takes place and he has to hold onto something to stay upright. He never leaves the smoke room.
I know this isn't historically correct, but the fictional characters are from the future and came to the Titanic by time machine. Their presence affects history, so if a historical inaccuracy is caused by a time-traveler, it's justified.

 

[Augusto Félix Solari]

Another thing to bear in mind are the extreme movements the stern section would have made in those first 90 second below the surface. Regardless of the small size of the cabins, these may have been enough to send everything up and down, causing severe damage to everything and everyone inside.

 

[PRR5406]

I think gases would be forced upward, walls breaking inwards, compression shooting anything liquid or gaseous out of the hull at an accelerated rate. While the air temperature is rising, the cold water spraying inward mitigates it. A person is lost in complete darkness, falling against loose furniture, horrific noises abounding. The stern passes below the surface and almost immediately, seawater is pushing in from all sides as the last air is squeezed into whatever pressurized compartments are available, including lungs, which would burst, but water pressure is applied equally on all sides. There is no breathing, no active thinking due to organ destruction. Finally, the remaining compressed air blows out of the hull as the sides collapse. Whoever might have been inside is shredded by collapsed steel, plaster, and wood. The only realization of what's happening occurs as the stern remains on the surface.
Everything is conjecture, of course.

 

[Arun Vajpey]

Yes it is conjecture. While I admit all those things that you have mentioned and maybe more eventually would happen to anyone trapped inside, one has to think about how long the person would remain conscious and aware before those events that you could describe.

Take the hypothetical Jane Doe in Cabin F180 as an example. if she gave up and went back there at 02:05 am and just lay down on her bed waiting for the end. The layout of that cabin would suggest that the bed was against the forward facing wall and so would have tilted to ahead down position as the stern rose out of the water. Assuming the present thinking that it did not rise above 15 degrees at most before the break-up, Jane Doe would have been tilted to a head down position on the bed. Then the lights would go out, plunging the room into pitch blackness. When the break-up occurred and the stern section fell back, she'd probably been thrown off her bed and would be injured by some of the furniture or fittings, but probably not severely enough to be knocked out. It was at that point that her real ordeal would start as the stern section started to flood rapidly though the open deck spaces. On F-deck it would probably have taken 60 to 90 seconds for the water to breach various obstacles and reach her cabin, during which time the stern would have turned to port and risen again, this time to a higher angle before sinking. If her bed was bolted to the floor (which I think it would have been), there would not have been much else in that tiny cabin to fly around and knock her out and so could have remained alive for all of those 90 seconds. Under the conditions that Jane Doe could have found herself in, those 90 seconds would seem awfully long.

 

[coal eater]

what about double bottom? how would it flood, or other words, if someone was trapped in empty space in double bottom of ship how it would effect itchance to survive sinking untill water manage to enter double bttom?