The stability of damaged ship

Discussion in 'Stability' started by xichyu, Apr 12, 2016.

  1. TANSL
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    TANSL Senior Member

    I think this is not possible in many damage cases. Think, for example, on a damage in a double bottom tank.
     
  2. gonzo
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    gonzo Senior Member

    Regardless of design, the water level (in calm conditions) will be the same inside and out. Otherwise, it would violate all the physical laws. The water level will equalize because atmospheric pressure is the same inside and outside of the vessel.
     
  3. mchl
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    mchl MCHL Stabilitycalculation

    you are right Gonzo !!
     
  4. TANSL
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    TANSL Senior Member

    improvements in the calculation of damage stability.

    I am amazed with your theories of physics. I'm glad to see that your opinions match. Congratulations
    How can be identical the water level inside than outside in a double bottom damage ?. Maybe I'm wrong understanding what you say. I would like an explanation from Gonzo, since he seems to dominate the laws of physics. Thanks.
     

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    Last edited: Apr 15, 2016
  5. NavalSArtichoke
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    NavalSArtichoke Senior Member

    MSC.281(85) is titled "Explanatory Notes to the SOLAS Chapter II-1 Subdivision and Damage Stability Regulations".

    These notes are intended to clarify some of the terms and language used in the new SOLAS Chapter II-1 Damage Stability regulations, which came into force after 2009, the so-called Probabalistic Method of evaluating damage stability.
     
  6. TANSL
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    TANSL Senior Member

    NavalSArtichoke, thanks for the clarification. I have not been very accurate in some of my statements.:(
     
  7. gonzo
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    gonzo Senior Member

    If the double bottom is closed, there will be an increase in pressure and very little water intrusion. The laws of physics say that for it to fill, as you indicate in your diagram, the pressure increases to infinity. Obviously that is nonsense.
     
  8. mchl
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    mchl MCHL Stabilitycalculation

    GONZO, Please stop : you do not help anybody with such a post.
    It's a nonsense to speek about calculations you never made !
     
  9. TANSL
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    TANSL Senior Member

    It is clear that the laws of physics are not available to anyone (Gonzo). Fortunately!
    Cheers, mchl, it is always positive argue with you.
     
  10. mchl
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    mchl MCHL Stabilitycalculation

    To be clear, we can say that it is not a problem of physics, but it is vorbidden to take into account trapped air in regulatory damage stability.
     
  11. Rabah
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    Rabah Senior Member

    Hi Gonzo,
    You have forgotten one very important condition - for tanks of a double bottom always there are air and measuring pipes, so that at accident of such tank outboard water easily on 100 % charges volume or if there was a fuel it expires and is changed outboard water.
    So that in this case Tansl rights, but he has no any right to scoff at you because his natural dropouts in knowledge on a ship theory as he showed it ignorance of methods of calculation on unsinkability are visible.
    That it was clear to all a file from Manual of Maxsurf Stability v.20 I publish.
    _____________________
    NA Razmik Baharyan
     

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  12. gonzo
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    gonzo Senior Member

    Rabah: you are correct, that is why I said that the level of the inside and outside water are the same. However, TANSL made a diagram that shows a tank with no air outlet. In that case, the internal pressure will equalize and only a small amount of water will enter.
     
  13. Don92
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    Don92 Principal Naval Architect

    TANSL I would have to disagree with your statement:

    "The liquid entering the ship as a result of the damage, as it is in contact with the sea, does not introduce any additional free surface effect."

    Flood water entering a vessel through a damage opening most certainly gives rise to additional free surface effects.
    Free surfaces have a large impact and influence in the flooding of a vessel post damage. This is particularly true during the progressive flooding stage where, depending on the complexity of the vessel's subdivision, water can rush through various compartments at different levels substantially reducing stability.
    While available regulatory instruments may not call for a dynamic damage stability assessment that addresses all underlying physical phenomena, this does not mean that these effects are not important.
     
  14. TANSL
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    TANSL Senior Member

    Don 92, I know it is necessary, obligatory, to take into account the effect of free surfaces. I think my statement is correct but I can not find resources to discuss this subject in a language I do not master. Note that I speak of compartments in contact with the sea and, in this case, has not yet been spoken of flooding various compartments, which introduces much more complexity to the issue. However I have no objection to analyze any rezoning that make me about it and I will not have difficulty in recognizing my mistake if I have no reason.
    Let's see if with the view of some experts and with the great help of MaxSurf User Guide, we can get to clarify the problem.
    I think this discussion can now begin to be interesting.
     

  15. mchl
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    mchl MCHL Stabilitycalculation

    If we are speaking of regulatory stability calculation, there is no dynamic effect of water in damage tanks/compartments to take into account.

    About free surface effect in damage tanks / compartments, its very clear :

    - at intermediate flooding stages, calculation can only be done with the added weight method. In this case, the weight of liquid is added to ship's displacement. Free surface effect must therefore be taken into account.
    - at the final stage of flooding, you have to use the lost buoyancy method. In this case, there is no need to take any free surface effect into account : it should be a non-sens : you cannot take into account the free surface moment of a liquid which is not included in the displacement.
     
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