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Physics inside a *very tall* hollow cylinder

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SilentReverence adopting kitteh from 3 tiles right 1 tile up Since: Jan, 2010
adopting kitteh
#1: Apr 5th 2011 at 11:30:46 PM

Hello all. I'm assuming this thread goes here as per the recent discussions in the Writer's Block subforum. Feel free to whip me good if that is not the case.

Anyway. I'm working on a fic and I want to start planning a particular setting, but I'm failing at extrapolating the physics to the adequate scale so I'd like to ask for some help to make the involved physics make sense (as could be interpreted in a Pokemon 'verse).

The setting. A Pokémon world with some nifty ruins left behind by some not-as-nifty Neglectful Precursor. Among them, a nice, hollow cylindrical structure about ~4 km tall with a radius in the 25-40 m range; essentially Made Of Nintendium although permeable to heat (but not to water of course!); cortex's thickness is about ~4 m*

.

The lower end of the cylinder digs about ~200m below ocean seabed and is isolated from the water; whereas the top end of the cylinder is likely open to the air about ~400m above sea level (leaving most of the structure surrounded by a ~3.5km deep ocean). The top area of the structure is linked to a platform similar in structure and size to an oil extraction platform. Essentially, the whole thing is a chimney sticking out of the seabed.

As for the plot, I have a character reaching the long-abandoned sea platform in order to continue a classical Fetch Quest. He will need to reactivate some specific devices in the platform in order to provide air and energy to the cylinder (not a problem), then go down the cylinder (big problem), excavate and fetch MacGuffin from the bottom end of the chimney (easy) and return safe to the surface (easy) before a plot-related timer goes out (hard). Although he'll have logistical assistance, he will have to do all the manual work himself, counting in his 'mons of course.

Now, the chimney itself has largely nonfunctional non-precursor equipment, so I assume that as part of the powerup procedure, the "hero" will have to activate whatever devices provide the structure with electricity and, most importantly, air supply. Although the chimney is noncompartmentalized in its Indestructium design, seals and pressure chambers were built every some hundred meters or so; however as the place has been "abandoned" for story purposes for quite a while, I'll bet even the best tech is faulty or nonworking at this point. The hero would have to either fix the seals (unlikely for a teenager, I guess, but with five 'mons and a HM Slave everything is possible), or stick with whatever environment naturally results in the place and try to not get himself killed.

Unfortunately, that is where my understanding of science fails me, as while I do have some knowledge on energy towers and gas flow principles, I'm definitively sure I don't know how to scale them to these requirements. And while yeah, this is a Pokémon world and I would be able to bend physics quite a bit, I'd rather limit myself to "correct" physics first and extrapolate from there without as much risk of an Ass Pull.

So, my most important questions here would be on what hell of an environment is the character going to find on his way down:

  1. Given the fact that the cylinder is submerged over 3 km into the ocean — how much does this effect the pressure and temperature in the inside (and would the invulnerability of the cortex reduce/augment the effect)?
  2. Am I right assuming that for a ventilation system to work at this scale, it has to mix piping (to inject/recycle air into the depts) and an air trade system (to recycle air between consecutive chambers)?
  3. On the piping, am I right assuming that piping air down requires a faster rate and lower temperature the deeper that air has to go into the circuit? How faster/colder has the injected air to go in, say, per kilometer for this scale?
  4. Assuming the top end of the chimney is open to the outside world unfiltered, what would the effect on the chimney (updraft? noise? utter destruction of unanchored props?) be when something like a tornado or windstorm is passing above the platform?
  5. Any other important factor that I am missing?

I'm trying to help myself by doing some research on Bernoulli effect and some famous undersea/undermountain traffic tunnels, and I think I get some of the concerns in ventilation timing, but even with those I think I'm not getting a hand at the effects on a scale I want...

Thanks in advance for any constructive help and commentary.

EDITed for list formatting

edited 5th Apr '11 11:36:40 PM by SilentReverence

Fanfic Recs orwellianretcon'd: cutlocked for committee or for Google?
storyyeller More like giant cherries from Appleloosa Since: Jan, 2001 Relationship Status: RelationshipOutOfBoundsException: 1
More like giant cherries
#2: Apr 6th 2011 at 6:36:16 AM

If the cylinder is indestructible, I don't think there will be much of a pressure difference. The only extra pressure would come from 4km of air. The conditions in the ocean are irrelevant.

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