Titanic submersible

[gerry maddenParticipant @gerrymadden53711]

Posted by Hopper on 23/06/2023 13:26:07:

The Guardian (see, I don't just read the red tops) quoted Professor Stefano Brizzolara, the co-director of Virginia Tech Center for Marine Autonomy and Robotics saying the water would enter the imploding vessel at 1,000kmh. No mention of where he got that figure from though. Still bloody fast. I think he said it would be all over in 20 milliseconds. Faster than the message "Darn" could get to the brain.

Edited By Hopper on 23/06/2023 13:34:39

mmm… I'm still wondering about this statement. Keeping it simple, if 'vacuuous' vessel under a hydrostatic pressure suddenly just disappeared, the velocity of the fluid would be zero at that time and point. It has mass, therefore it accelerates. It must be the fluid at the boundary of the collapsing cavity that has maximum velocity, as it has nothing to stop it. The velocity of the fluid crossing the original boundary line will drop off quite quickly due the diminishing flow-rate, as the cavity volume tends towards zero.

My thinking is that if this chap wanted a headline to give to the baying press, he would quote that of the 'final velocity' of the fluid at the very centre of the vessel/cavity, and not that of the fluid "entering the imploding vessel" (ie. crossing the original boundary), perhaps ?

……perhaps I'm getting a bit carried away. Its not as though I have nothing else to do. I think I still harbour a lingering irritation over those people that used to say, things like "if you don't wear a seatbelt you will hit the dashboard with the force of an elephant"

gerry

[HopperParticipant @hopper]

Posted by gerry madden on 24/06/2023 12:36:10:

Posted by Hopper on 23/06/2023 13:26:07:

The Guardian (see, I don't just read the red tops) quoted Professor Stefano Brizzolara, the co-director of Virginia Tech Center for Marine Autonomy and Robotics saying the water would enter the imploding vessel at 1,000kmh. No mention of where he got that figure from though. Still bloody fast. I think he said it would be all over in 20 milliseconds. Faster than the message "Darn" could get to the brain.

Edited By Hopper on 23/06/2023 13:34:39

mmm… I'm still wondering about this statement. Keeping it simple, if 'vacuuous' vessel under a hydrostatic pressure suddenly just disappeared, the velocity of the fluid would be zero at that time and point. It has mass, therefore it accelerates. It must be the fluid at the boundary of the collapsing cavity that has maximum velocity, as it has nothing to stop it. The velocity of the fluid crossing the original boundary line will drop off quite quickly due the diminishing flow-rate, as the cavity volume tends towards zero.

My thinking is that if this chap wanted a headline to give to the baying press, he would quote that of the 'final velocity' of the fluid at the very centre of the vessel/cavity, and not that of the fluid "entering the imploding vessel" (ie. crossing the original boundary), perhaps ?

……perhaps I'm getting a bit carried away. Its not as though I have nothing else to do. I think I still harbour a lingering irritation over those people that used to say, things like "if you don't wear a seatbelt you will hit the dashboard with the force of an elephant"

gerry

 

 

Yes that sounds about right. (Not the elephant bit!) Water at the periphery would start off at 0kmh and accelerate from there. Still, with 6,000psi behind it, it will not be hanging about. Until it hits the water coming in from the opposite side, with literally crushing results for anything in between.

Edited By Hopper on 24/06/2023 13:17:16

[Michael GilliganParticipant @michaelgilligan61133]

A simplistic alternative view … At the instant that the tube fails, a column of water [of whatever head is relevant] descends to fill the space. … There isn’t enough time for anything to significantly change shape.

MichaelG.

[HopperParticipant @hopper]

I think it might be more complicated than that though. A google search for "fluid dynamics of implosion" reveals a world of head-achingly complex books, PhD theses and theories, like THIS one. It seems it is not necessarily a certain thing and depends on many factors.

Intuitively though, I would expect water to rush in simultaneously from the sides and bottom, not just the column from above, because pressure is virtually the same all round. Close enough to make no difference.

This paper HERE raises several interesting points. One is the compressibility of seawater at that depth and pressure means the fluid will initially expand as it is exposed to the low pressure void in the collapsing vessel, presumably adding to the kinetic energy involved. This results in a low pressure in the surrounding water, followed by a spike as the water rushing in hits other water and comes to a stop. The other point is that a brittle material (eg carbon fibre) will make the shock of the implosion greater than if it is a more ductile material such as a metal.

Still no clue as to where the various professors are getting specific figures for the speed of the water in an implosion at that depth. I suppose they could apply the old F = M*A and calculate something over the 20 milliseconds of time for velocity. No idea how you would apply it in a fluid situation like this. Its way above my pay grade.

[Michael GilliganParticipant @michaelgilligan61133]

Posted by Hopper on 24/06/2023 14:14:13:

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This paper HERE raises several interesting points.

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Excellent find, Hopper

I have downloaded the book, and will see how much/little of that paper I understand this evening

MichaelG.

[Michael GilliganParticipant @michaelgilligan61133]

Of course, I couldn’t resist having a quick skim through

Unfortunately although the relevance to deep sea exploration vehicles is mentioned, all of the reporting concerns experiments at much shallower depth.

I am, however taking the liberty of posting this one graph, which I think tells us a lot !

.

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Whatever clever analysis we might hope to do, or see to be done by others … I think the X-axis pretty-much says it all.

MichaelG.

[Michael GilliganParticipant @michaelgilligan61133]

Another paper worth looking-at [free download]
Again, the scale of things is not representative of Titan

**LINK**

https://royalsocietypublishing.org/doi/10.1098/rspa.2013.0443?url_ver=Z39.88-2003&rfr_id=ori%3Arid%3Acrossref.org&rfr_dat=cr_pub++0pubmed

MichaelG.

[Nicholas FarrParticipant @nicholasfarr14254]

Hi, there is a lot of this above my pay grade, but of course the highest pressure is at the bottom of the water column, which many of us had probably been shown by the simple lab experiment at school Old School Experiment so I suppose the implosion could have started at the bottom of the tube, assuming that is what had failed, but of course the actual pressure difference between the bottom and the top of the sub, wouldn't have very much at that depth. Unlike a compressed gas, there isn't an equal pressure in all directions in a column of water. During some of my day jobs, I've been involved in lock gate and stop logs, and the hardest part to stop leakage is at the bottom of them. Below is a photo of one set of two that a workmate and myself, were contracted to install the frames and the logs, in a brand new eel pass on the River Dove, near Stoke-on-Trent. Being brand new, we didn't get any leakage problems thankfully.

Regards Nick.

[Michael GilliganParticipant @michaelgilligan61133]

Useful input, from a man who knows rather than just ponders !

“Unlike a compressed gas, there isn't an equal pressure in all directions in a column of water.”

… Thanks for sharing your practical experience, Nick

MichaelG.

Edited By Michael Gilligan on 24/06/2023 17:13:33

[Nicholas FarrParticipant @nicholasfarr14254]

Hi, having a quick look through the book Hopper linked too, and seeing how those tubes have flattened out in Fig 18 section 4.2., in my old job, they had a submersible dewatering pump, which weighed about 3 Tonnes, and it would pump water for about two miles, however the 10" PVC pipeline was going uphill for a short distance before dipping slightly and then a very sallow downward long slope to the outlet, this was across a quarry, all was fine and dandy, but when the level of the water got low enough, the pump automatically cut out, which was fine. The problem was when it cut in again, and it pumped for a short while and then tripped several times for no apparent reason, the electrician was called to look at it but found no problems, so it was assumed that something had got into it and was causing to much of a back pressure. So to cut a long story short, we had to look inside the pipeline, and it turned out that where the pipeline reached the highest point, which was a little below ground level for about 20M back towards the pump, about 6M of the 10" PVC pipe had been suck as flat as those tube in Fig 18 mention above. No thought was given to allow air to be drawn back into the pipeline when the pump stopped during installation, I had no involvement in putting the pipeline in, I might add, as it was a contacted out job, but it does show the power of our meagre 14 psi of Air we live in, and a somewhat small amount of water running downhill.

Regards Nick.

[Nicholas FarrParticipant @nicholasfarr14254]

Hi MichaelG, thanks for your vote of confidence.

Though it is surprising how many people you think ought to know these sort of things, actually don't.

Regards Nick.

[JAParticipant @ja]

The sum is easy. Using the incompressible Bernoulli equation (the second simplest equation used in fluid dynamincs), I can say without doubt that the water will have a velocity of 944 ft/s (1036 km/hr).

All you have to be is the professor of a university and the press will believe you.

Bernoulli is only relevant for steady flow.

JA

Edited By JA on 24/06/2023 18:09:05

Edited By JA on 24/06/2023 18:15:23

[Robert Atkinson 2Participant @robertatkinson2]

Posted by Nicholas Farr on 24/06/2023 18:01:06:

Hi MichaelG, thanks for your vote of confidence.

Though it is surprising how many people you think ought to know these sort of things, actually don't.

Regards Nick.

Indeed. I was once asked to look at the electrical supply for a pump being fittted to an aircraft. It was to pump fuel from a belly tank to a high wing tank. The pump was in the wing. I was not popular when I pointed out that at cruise altitude there was not enough air pressure for it to work. The highly qualified system designer did not realise that it the pump only created a vacuum and air pressure pushed the fuel up the pipe. He didn't belive me but I attended a meeting with the pump supllier who promply said their product would not work when he was shown the concept drawing. They ended up with a pump in the belly tank. I also pointed out that on a hot day the fuel would "boil" if they tried to lift it by vacuum. They then realised that while I was employed s a Avionics designer I was also experiened and qualified on fuel systems…..

Robert.

 

Edited By Robert Atkinson 2 on 24/06/2023 19:13:12

[Nicholas FarrParticipant @nicholasfarr14254]

Hi Robert, taking about vacuum pumps, I had to give a new chap a water pump job, you know the sort of person, been everywhere and what he didn't know, wasn't worth learning about. Anyway he had to set up a portable land based pump, which had a vacuum pump to prime the water pump, after about an hour setting out all the pipework etc., he came back to me to say the pump wouldn't pump the water, and asked if I could have a look. Well the pit he had to pump out was about 50 Ft. below a bank, when I went to look, I saw the pump on the bank and 50 Ft. of suction pipe going down to the pit. I simply told him there and then that he would have to alter his pipes and move the pump down to the lower space next to the pit, as the vacuum wasn't capable of lifting the priming water to the height of the bank, he doubted me, but I told him he had no choice, he wasn't very happy to have to move the pump, but soon realised I was right when it pumped within a minute or so after starting it, once he got it into the correct place.

Regards Nick.

Edited By Nicholas Farr on 24/06/2023 21:03:45

[derek hall 1Participant @derekhall1]

Where I work, we employ a physicist who specialises in fluid dynamics, he has a phd in the subject…I will ask him on Monday what he thinks happened during the failure and report back.

All the best

Derek

[Michael GilliganParticipant @michaelgilligan61133]

Well-played, Derek

MichaelG.

[FulmenParticipant @fulmen]

What I don't understand is why they were running at atmospheric pressures. IIRC you can handle 2-3bar abs without decomp, and you have two hours for that if needed.

[BazParticipant @baz89810]

Fulmen 30 odd psi inside would not have made any difference when you have got a few thousand psi on the outside. Please correct me if I am wrong.

[Roger Williams 2Participant @rogerwilliams2]

With 6000psi acting on every square inch of your body , you will be turned to dust 150 milliseconds before your brain could register it happening . At least they didnt suffer.

[Nigel Graham 2Participant @nigelgraham2]

Fulmen –

Submarines and submersibles normally work at atmospheric pressure inside.

The object of the design is to make the pressure-hull withstand the external pressure, which increases at the rate of 1 Atmosphere for every 10m depth, with a factor of safety – and repeatably.

It was only civil-engineering caissons that were pressurised internally, and it was using these that caused the first cases of "the bends". ( I don't know if they are still used, though obviously with much more stringent practices and precautions).

[FulmenParticipant @fulmen]

@Baz: You're right, I have been in the sun too long today. I started thinking in ratios, not difference for some reason.

[Ady1Participant @ady1]

The high pressure systems were so divers could work at depth, entering and leaving the capsule

Hazardous stuff, even nowadays, they also had to breathe some weird mixtures of gasses

[HopperParticipant @hopper]

THIS BBC article contains the following, from a retired submarine officer:

"When a submarine hull collapses, it moves inward at about 1,500mph (2,414km/h) – that's 2,200ft (671m) per second, says Dave Corley, a former US nuclear submarine officer.

The time required for complete collapse is about one millisecond, or one thousandth of a second.

A human brain responds instinctually to a stimulus at about 25 milliseconds, Mr Corley says. Human rational response – from sensing to acting – is believed to be at best 150 milliseconds.

The air inside a sub has a fairly high concentration of hydrocarbon vapours.

When the hull collapses, the air auto-ignites and an explosion follows the initial rapid implosion, Mr Corley says.

Human bodies incinerate and are turned to ash and dust instantly."

…………………………………………………………..

Which is probably the source of the "turned to dust" that seems to be mentioned everywhere on the media. Sounds like something crews are all taught at submarine school.

But is a submarine the same situation? Depth is nowhere near the Titan's, so pressure would be far less. Submarine is much larger, giving more time and distance for the water to accelerate before meeting the oncoming water, so possibly higher velocity.

And the auto-ignition of hydrocarbons under compression in the air in a sub is probably not relevant to the Titan. Submarine is full of all sorts of oils and solvents and possibly diesel fuel for standby generators etc. Certainly a conventional sub is awash in diesel fumes from the main engines and their fuel supply, some of which inevitably ends up down in the bilge before being run through a separator and stored in a tank to be environmentally consciously disposed of in port. My ex-submariner co-workers at the shipyard building Collins subs told me the stink of diesel fuel was a pervasive fact of life in a sub, rivalled only by human flatulence, which was elevated to an artform as the main source of entertainment. They were all crazy.

 

 

 

Edited By Hopper on 25/06/2023 00:24:50

Edited By Hopper on 25/06/2023 00:26:46

[HopperParticipant @hopper]

Posted by derek hall 1 on 24/06/2023 20:41:14:

Where I work, we employ a physicist who specialises in fluid dynamics, he has a phd in the subject…I will ask him on Monday what he thinks happened during the failure and report back.

All the best

Derek

Looking forward to hearing what he says. Well done.

[HopperParticipant @hopper]

Posted by Steviegtr on 25/06/2023 00:34:13:

You are probably all great model engineers. Making little things & being proud of what you have achieved.. You probably also think you are all the Oracle on any subject.

But I can only assume if any of the families of the departed see these forum posts , they will probably be very overcome with grief.

I implore all of you to stop airing your stupid knowledge that is derived from the internet.You all compounded together probably have the intelligence of a standard carpet flea.

Let these people mourn in peace without telling everyone how you know evrything. Lots of you talk about how it is wrong to go visit the graves of departed people.

But you will discuss how they were killed. You are no better.

This thread should be stopped.

Steve of steviegtr Youtube.

Edited By Steviegtr on 25/06/2023 00:36:04

With the exception of the last line of the last quote from the US submariner, which was included to explain the pervasiveness in the media of statements about turning to dust, the discussion here is purely the engineering aspect of what happened to the vessel itself from a technical viewpoint. And nobody is claiming to know everything. Quite the opposite in fact. Your personal insults are quite out of line.

This stuff is going to be all over the media for the next six months and more as the official inquiry and various legal actions etc proceed. This obscure thread makes not one jot of difference in the overall picture.

 

 

 

Edited By Hopper on 25/06/2023 00:54:27

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