Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

Underwater Pressure

  1. Jul 22, 2010 #1
    Ok I am almost positive this doesn't work or it would be used in deep submersibles, but I am at a loss as to why.

    About every 33 or 34 feet pressure underwater increases by 1 atm. So a submarine at 33 feet under water with 1 atm internal pressure would have 2 atm of external pressure. Increase that to 330 feet and you have 10atm which is a bit harder to handle.

    I am not sure about the biology and what kind of air pressure humans are capable of breathing and living comfortably in but for simplilcity sake can just say that 1 atm is desired.

    Now many materials can not withstand this kind of force, most submarines can only dive to 200-300 meters and this isn't even for extended periods of time.

    But why doesn't multiple hulls / walls in the case of buildings work? My real question has to do with underwater structures.

    Say you have something like this

    (10atm)--| (7atm) | (4atm) | (1atm) |

    A series of hulls and chambers with slowly reducing pressures. The outermost one is the water, and as you move in its a series of sealed chambers, or possibly open to a moon pool. untill there is an inner chamber at 1 atm. Now would the 10atm pressure apply to all internal chambers? or would it only apply to the outer one? If it would pass through and apply pressure to all chambers how does it do this? would distance between the chambers matter? I have a hard time picturing an outer wall and then 20 feet of pressurized air and then another wall having a perfect transfer of force. It has been a long time since I have taken physics and feel I am missing something simple
  2. jcsd
  3. Jul 22, 2010 #2
    What do you mean doesn't work?

    Multiple stages are perfectly feasible, but what would you gain?
  4. Jul 22, 2010 #3
    needing materials that would not be required to withstand immense pressure say at 660 ft, a straight wall structure would not be able to withstand a 19atm difference without buckling. A series of smaller differences would make for less costly materials with less precision in their construction + allow for failure.
  5. Jul 22, 2010 #4
    I'm sorry to disillusion you but there would still be the same global stresses/forces for the barrier to cope with, whatever its construction.

    Imagine a ring, with 10 atm outside the outer circle and 1 atm inside the inner and some sort of internal structure between the rings. Whatever this structure it will have to conform as stated above.
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook