Simulating Costa Concordia

Discussion in 'Boat Design' started by APP, Jan 17, 2012.

  1. smartbight
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    smartbight Naval Architect

    Freeship/Delftship Artist volunteer ?

    To get better results we'll need Freeship/Delftship artists on the forum who can volunteer a couple of weekends to refine the bow & stern on the preliminary lines shown. NA students can apply !
    We have a 'rough' model & enough pictures and info that we can post to construct a 99% accurate model (no superstructure).

    The reward: Your name, for a first, in the cruise ship category in Martjin's excellent Freeship/Delftship data base of 200+ hulls.
     

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  2. nettersheim
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    nettersheim Consultant

    Considerable job already carried out, congratulations.

    Hope to see first results of damage stability results shortly...but I kow it is still a lot of work ! Have you sufficient in formation to build up the internal part of the model for these damage stability calculations ?

    Francois-Xavier Nettersheim
     
  3. IEWinkle
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    IEWinkle Retired Naval Architect

    Whilst applauding your efforts I must refer you back to my Post 20 which gives the Lpp for this vessel as 247.4m The waterline length will be a little larger than this (due to the overhang of the stern beyond the rudder stock) but not 284.44m as given in the Hydrostatics Sheet This explains the significantly lower Cb that you quote at 0.6447 rather than my earlier estimate of nearly 0.7. This extra length will have a significant effect on the the waterplane inertias and hence the intact and damaged stability estimates, so I would caution any further hull refinement until the length issue is addressed. I also note the Midship Coefficient of 0.9199 which seems very low for a vessel of this type. I'm afraid you will have to make the form somewhat shorter and fatter. I also do not understand a Beam Overall of 35.761m, Beam on Waterline of 35.753m and a Design Beam of 35.5m. I hardly think that this vessel has a shell thickness of 0.105m. 15mm would be a good working estimate at this stage. I also do not understand a midship location of 184.51m with an LCF of 128.68m and LCB of 139.98m. Your midship location is clearly not to any definition I know.

    I note from post 54 below that an assumed bilge radius of 2.2m would lead to a Mishship Section Coefficient of 0.9929.

    I hope my comments help towards developing a more accurate hull model and hydrostatics and look forward to your results.
     
    Last edited: Feb 8, 2012
  4. Leo Lazauskas
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    Leo Lazauskas Senior Member

    Do you have a good plot of the bathymetry of the area?
    (I'm more interested in the hydrodynamics than other aspects.)

    All the best,
    Leo.
     
  5. smartbight
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    smartbight Naval Architect

    This is the only 3D 'bathymetry' of the area we have seen. I think you are looking for closer details?
     

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  6. smartbight
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    smartbight Naval Architect

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  7. APP
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    APP Junior Member

    Excellent! Can you please post the freeship fbm file here?
    Regards
    APP
     
  8. Leo Lazauskas
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    Leo Lazauskas Senior Member

    Thanks, that is getting close to what I need.

    The L/B is Ok for Michlet, but I'm not interested in just the resistance.
    I will try to estimate the squat and effect on resistance using Flotilla and
    some other codes.

    I'm puzzled by a couple of things...
    Just before impact, the speed increased from 15.3 knots to about 16 knots.
    Did the captain increase speed deliberately?
    Or did a reduction of resistance in shallower water cause the speed to increase?
     
  9. smartbight
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    smartbight Naval Architect

    Here it is. Versions 2.6 and 2.0 in case you use an older Freeship.
    v 2.6 will show outboard profile background image as seen on screen dump.
    Bilge radius is around 2.2 m amidships as per photo ? (doesn't look like a true radius). That radius increases fwd & aft.
    We will post more pics of bow & stern of CC or sisterships.
    Are you doing the modeling yourself ?
     

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  10. APP
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    APP Junior Member

    Very Nice. Thanks. I am not doing any modeling.
     
  11. smartbight
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    smartbight Naval Architect

    As we said before this is a very rough model that one of our drafters started.
    There is still a long way to go before it resembles CC lines.
    Thanks for letting us know.
     
  12. IEWinkle
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    IEWinkle Retired Naval Architect

    Estimated extent of flooding

    For those interested in a simulation of the incident I have analysed the photograph of the vessel as it grounded on the shore for draughts, trim & heel comparing it with a photo of the vessel in port.

    The results suggest a trim by the stern of 4.95 m between perpendiculars giving draft aft of 12.05 m and draft forward of 7.10 m. Heel would appear to be about 13.2 degrees to starboard putting the bulkhead deck about 3 m underwater at its starboard after end. The estimated inflow of water (lost buoyancy or added weight) for this condition based on a WPA of about 8700 sq m would be about 12,500 tonne (about 24% increase over her normal loaded departure displacement!). Assuming most of this to be above a relatively intact double bottom (post 54 shows longitudinal subdivision about 7.5 m inboard of the side) about 2 m deep, gives a reasonable basis to start considering the location and extent of flooding once a reasonable set of hydrostatics can be estimated.

    I hope this helps
     

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    Last edited: Feb 14, 2012
  13. IEWinkle
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    IEWinkle Retired Naval Architect

    Costa Concordia – a Scenario for Progressive flooding and Capsize

    Analysis of the profile photograph and cabin arrangements (see PDF file) – particularly of Deck 1 (Olanda) suggests that the structure of the ship is made up of a series of equal bays of length 2.9 m (one overall cabin spacing) which corresponds to the spacing between the large transverse web frames supporting the longitudinal frames running throughout the lower structure, implying a transverse frame spacing of 725 mm through the double bottom (in the zone of damage). Multiples of these bays (4, 5 & 6) allow the position of pillars between lifeboats to be established giving the possibility to reference the damage location fairly accurately in terms of web and frame locations. This allows an estimate of the location of the major damage (of the soft side shell) on the port side as running from 37.7m forward of the AP to 74.4m forward of the AP. The AP appears to be 10 m forward of the transom at the Load Waterline, in line with the twin rudder stocks. The damage to the bilge area only appears to run forward to about 92.8 m forward of the AP.

    Overlaying this information on the small profile drawing (see PDF file) amongst the passenger deck plans identifies at least four (from a bulkhead around 31.9 m forward of AP to one at 89.9 m forward) and possibly five compartments along the length (up to 101.5 m forward) that will have been compromised. The ‘definitely flooded’ compartments would include the two main diesel generator rooms and the motor room aft - the after generator and motor rooms subject to immediate inundation, with the forward generator room flooding more slowly (hence the blackout after 10 mins). Overall damage length therefore varies from 58 m (min) to 69.6 m and will include a substantial length of double bottom port wing tanks of some 14 sq m cross-section which were probably empty in this condition (no obvious oil leakage and no significant ballast). If we assume about 60 m of these tanks were flooded together with a rock of some 70 tonne (immersed weight) there would be a port listing moment of some 880 tonne at about 14.25 m from the centreline which would displace the vessel’s centroid by about 0.244 m. This would produce an initial list of about 7 degrees to port if the GM is assumed as 2 m.

    It is interesting to speculate whether in the 10 mins that power was available, ballast might have been pumped into the starboard wing double bottom tanks to counteract this list?

    Analysis of the photo as the vessel hits the shore heeling to starboard shows a trim by the stern of 4.95 m between perpendiculars giving draft aft of 12.05 m and draft forward of 7.10 m. Heel would appear to be about 13.2 degrees to starboard putting the bulkhead deck about 3 m underwater at its starboard after corner. The estimated inflow of water (lost buoyancy or added weight) for this condition based on a WPA of about 8700 sq m would be about 12,500 tonne (about 24% increase over her normal loaded departure displacement!). If we deduct the 880 tonne loss of buoyancy discussed above, that leaves 11,620 tonne to fill the compartments above the double bottom at an assumed permeability of 85%.

    Noting the presence of a deck at side about 7.2 m above base and assuming all water was contained by this, then the flooded length would be 72.2 m. If this deck is assumed to only run for 25% of the breadth each side outboard of a machinery casing which is flooded to an average depth of 8.715 m (mean local draft 10.715 m), the flooded length would be 54.0 m. Should the engine casing be shorter than 54 m (more than likely), then the overall flooded length could well lie up to the minimum length 58 m or somewhat beyond. This assumption provides the basis for stability if the wing deck spaces formed by the side deck and casing remain fully buoyant and would account for the initial port list rapidly reducing from 7 degrees at an early stage.

    For the vessel to heel to starboard some of this starboard wing buoyancy must have been lost through progressive flooding in addition to any earlier ballast transfer to starboard. It therefore seems likely that in evacuating the machinery spaces, one or more doors giving access to the starboard wing spaces may have been left open above the 7.2 m deck which allowed progressive flooding to establish itself shortly before the vessel grounded, resulting in the 13.2 degree list to starboard deduced from the photo. Continuation of this flooding would have resulted in the vessel’s increasing list to starboard which would have eventually immersed the passenger decks leading to complete capsize onto the rocky shelf.
     

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  14. nettersheim
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    nettersheim Consultant

    Thank you very much for your impressive and very interesting attempt to draw out a possible scenario for progressive flooding.

    Regarding your idea to speculate whether the crew might have tried to use ballasts for counteracting the initial list on port, I personnally doubt that any action has been carried out.

    Even if it is confirmed that some power has been available for approx. 10 mins after the accident, I can't imagine that with water rushing inside engine rooms they have had any possibility -and even the idea- to fight the list. The engine officer on watch in engine control room together with chief-engineer have according to what I have read here and there quite early understood that the situation was critical and hopeless. I read somewhere that they have tried to run the bilge system but obviously it was desesperate action with such huge flooding : pump capacity of few hundred cubic meters per hour against approx. 10, 20 (?) x 1000 cubic meters per hour of massive water ingress !
     

  15. smartbight
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    smartbight Naval Architect

    We used the brochure you provided and blew it up to scale. The bulkheads are the ones shown on the brochure. The spacings shown do not give us a constant frame length yet. If you can mark up the drawing or write down the corrections needed, we can have it revised.
     

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