Seakeeping software for offshore & barges

Discussion in 'Software' started by offshoreguy, Sep 26, 2009.

  1. offshoreguy
    Joined: Aug 2009
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    offshoreguy Junior Member

    I am triying to simulate stability of flat multihulls hulls to be used in offshore installations.
    I tried using seakeeper, but it seems does not work with such structures, and I have following problems:

    When using catamarans, in the animation, it appears as a monohull
    I can not use multihulls because it cannot connect lines from one hull to another
    If I animate structures with LOA=BOA at 45 degrees from waves, it appear as roll lot higher than pitch. See capture:
    [​IMG]

    So perhaphs this sw is not good for this structures or I have done something wrong.
    Do anyone know a better sw not very expensive?
    I found something at web about waveload (used in Lloyds) and shipmotion (proteus)
     
  2. Ad Hoc
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    Ad Hoc Naval Architect

    If it is for a real project, ie with money, then tank test, or if you prefer sw route, buy sw that is suitable for this type of application, but usually very very expensive!

    There are no short cuts with this...
     
  3. Leo Lazauskas
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    Leo Lazauskas Senior Member

    Depends on what you consider "expensive".

    Have you had a look at the capabilities of the program WAMIT?

    Good luck!
    Leo.
     
  4. Ad Hoc
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    Ad Hoc Naval Architect

    I've not personally used WAMIT, but on a project we were involved in (the client used WAMIT as their first hit for design) several years ago the results were shockingly bad when compared to test tanks and other real data from many independent sources. Also, when compared to requirements by Class, as a basis for design. So I personally wouldn't use WAMIT as a source of data for a real project for real money.
     
  5. offshoreguy
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    offshoreguy Junior Member

    Of course at the end, the tank test is the best. But I have a lot of design to compare before and I would like try modifications in order to trim the design before. Also I would not like spend time learning not suit packages
     
  6. Ad Hoc
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    Ad Hoc Naval Architect

    Once you do find a sw that gives "reasonable" answers, they of course very good and quick at sensitivity analysis.
     
  7. offshoreguy
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    offshoreguy Junior Member

    Other software I found where:

    Wasim
    Splash http://www.panix.com/~brosen/ for Americas cups
    Aqwa (Ansys)
    Lamp-2 (Simulates large waves, but seems to be academic codes, where is the sw?

    Swam
    Waveload
    (Shipmotion)

    Shipmopc only monohulls

    Have anybody tested any of them?
     
  8. Leo Lazauskas
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    Leo Lazauskas Senior Member

    Have you looked at the US Navy's code SMP (Ship Motion Program)? Although it's a fairly old strip code, it might be useful because it's free and you get the Fortran source which you can modify and compile.

    I used SMP on some simple head seas calculations for some America's Cup contenders about 12 years ago and it gave reasonable results, at least as good as SPLASH and some other expensive codes.

    A warning though. The Fortran code is a bit of a nightmare to pick through. I hacked it to include wave-making and squat of thin monohulls but I never got around to releasing "FLOTSM" into the public domain because I hate writing manuals.

    Good luck!
    Leo.
     
    Last edited: Oct 1, 2009
  9. offshoreguy
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    offshoreguy Junior Member

    Thank you Leo, I where looking for the code and I found the Wolfon unit (I think is not the same) : http://www.wumtia.soton.ac.uk/software.html (1500 Bpounds)
    Proteus package is based on the fortran

    I worked on fortran for Ansys 12 years ago, but I prefer C++ (I where thinking about having a command line sw in order to be used in a 3d viewer)

    Where can I find the ship motions?

    Can I import IGES, STEP or other similar 3-d shapes?
     
  10. Leo Lazauskas
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    Leo Lazauskas Senior Member

    No, the Wolfson one is different.

    Here's an abstract describing the program, just in case it's not suitable. The best way to get it is to contact CARDEROCK directly. Sorry, but I don't know the specifics of their address etc.

    SMP93-PC: Standard Ship Motion Program for Personal Computer with Small Boat Capability
    Authors: T. C. Smith; W. G. Meyers; NAVAL SURFACE WARFARE CENTER CARDEROCK DIV BETHESDA MD HYDROMECHANICS DIRECTORATE

    Abstract: The Standard Ship Motion Program, SMP, was developed at the Carderock Division, Naval Surface Warfare Center, and documented in 1981 as a prediction tool for use in the Navy's ship design process. SMP provides predictions of the response of a ship advancing at constant forward speed with arbitrary heading in both regular and irregular seas. In 1984, a number of corrections and enhancements were finished and documented. In 1987, the Naval Sea Systems Command installed an undocumented FORTRAN 77 version on their Digital VAX hardware. From there SMP migrated to the personal computer. Additional features and improvements have been made. Predictions of horizontal force estimator were incorporated into SMP. An option was added to reduce run time and minimize unwanted output. Extra wave frequency sets designed for small boats were also added. Ship motions, Small boats, Computer manual.

    You're a funny guy. Here's the nightmare that is the SMP input form.


    HD.DAT DDG51 BY JWK 7/19/83 DRAFT - 20.69 FT TRIM - 0.00 FT
    6 0 1 1 0 1 0
    FEET 1.9905 32.17400.00001279
    466.0000 58.9221 20.6900 8500.00 30.0000 30.0000 0.0000
    4.7700 0.1100 24.2400 .2500 0.4000 .2500
    23 1
    0.0000 0 0
    0.0000 0.00
    0.0000 0.00
    0.2500 10 0
    0.2500 0.00 4.45 8.17 8.92 5.87 2.04 0.48 0.48 0.69 1.18
    0.2500 -9.58 -9.04 -6.63 -2.37 0.83 3.18 7.22 11.72 16.21 20.69
    1.0000 10 0
    1.0000 0.00 4.25 7.95 8.19 4.99 2.27 2.27 2.83 3.66 4.74
    1.0000 -8.76 -8.26 -6.20 -2.26 0.58 3.82 8.07 12.33 16.54 20.69
    2.0000 10 0
    2.0000 0.00 1.48 1.12 2.75 4.09 5.35 6.61 7.84 9.07 10.31
    2.0000 -4.70 -2.95 0.07 2.85 5.79 8.76 11.73 14.72 17.71 20.69
    3.0000 10 0
    3.0000 0.00 2.54 4.57 6.40 8.12 9.78 11.36 12.83 14.24 15.60
    3.0000 0.00 1.19 3.32 5.63 8.02 10.45 12.94 15.49 18.08 20.69
    4.0000 10 0
    4.0000 0.00 3.09 5.78 8.32 10.69 12.90 14.96 16.86 18.61 20.21
    4.0000 0.00 0.97 2.87 4.98 7.27 9.72 12.31 15.00 17.80 20.69
    5.0000 10 0
    5.0000 0.00 3.54 6.81 9.92 12.83 15.51 17.96 20.14 22.05 23.72
    5.0000 0.00 0.70 2.27 4.15 6.33 8.78 11.46 14.37 17.47 20.69
    6.0000 10 0
    6.0000 0.00 3.88 7.62 11.19 14.53 17.57 20.25 22.54 24.47 26.11
    6.0000 0.00 0.44 1.60 3.20 5.24 7.70 10.56 13.73 17.13 20.69
    7.0000 10 0
    7.0000 0.00 4.14 8.22 12.17 15.87 19.13 21.91 24.23 26.15 27.69
    7.0000 0.00 0.24 0.97 2.22 4.10 6.65 9.73 13.16 16.84 20.69
    8.0000 10 0
    8.0000 0.00 4.33 8.64 12.86 16.84 20.30 23.17 25.49 27.32 28.68
    8.0000 0.00 0.13 0.56 1.49 3.18 5.77 9.01 12.65 16.58 20.69
    9.0000 10 0
    9.0000 0.00 4.46 8.90 13.30 17.49 21.19 24.22 26.52 28.12 29.23
    9.0000 0.00 0.10 0.43 1.19 2.68 5.14 8.40 12.22 16.37 20.69
    10.0000 10 0
    10.0000 0.00 4.53 9.04 13.52 17.84 21.73 24.89 27.14 28.52 29.46
    10.0000 0.00 0.11 0.46 1.17 2.51 4.80 8.03 11.95 16.26 20.69
    11.0000 10 0
    11.0000 0.00 4.53 9.04 13.51 17.83 21.75 24.95 27.22 28.57 29.48
    11.0000 0.00 0.13 0.52 1.25 2.58 4.84 8.03 11.93 16.25 20.69
    12.0000 10 0
    12.0000 0.00 4.45 8.87 13.24 17.44 21.30 24.62 27.09 28.51 29.41
    12.0000 0.00 0.23 0.82 1.74 3.23 5.44 8.41 12.10 16.32 20.69
    13.0000 10 0
    13.0000 0.00 4.30 8.54 12.69 16.66 20.43 23.84 26.57 28.21 29.21
    13.0000 0.00 0.46 1.37 2.61 4.33 6.47 9.13 12.47 16.47 20.69
    14.0000 10 0
    14.0000 0.00 4.05 7.99 11.83 15.56 19.19 22.62 25.54 27.56 28.77
    14.0000 0.00 0.86 2.23 3.83 5.71 7.75 10.12 13.07 16.71 20.69
    15.0000 10 0
    15.0000 0.00 3.45 6.92 10.50 14.10 17.62 21.03 24.19 26.56 28.03
    15.0000 0.00 1.74 3.74 5.53 7.30 9.21 11.31 13.76 16.97 20.69
    16.0000 10 0
    16.0000 0.00 1.91 4.79 8.33 11.91 15.45 18.94 22.26 25.02 26.89
    16.0000 0.00 2.98 5.59 7.26 8.87 10.58 12.38 14.47 17.25 20.69
    17.0000 10 0
    17.0000 0.00 2.43 5.41 8.56 11.72 14.84 17.93 20.96 23.57 25.28
    17.0000 5.48 7.75 9.30 10.48 11.65 12.91 14.25 15.71 17.81 20.69
    18.0000 10 0
    18.0000 0.00 2.76 5.53 8.29 11.05 13.79 16.51 19.13 21.51 23.21
    18.0000 11.61 12.28 12.91 13.55 14.25 15.00 15.82 16.90 18.44 20.69
    19.0000 10 0
    19.0000 0.00 2.37 4.74 7.10 9.46 11.81 14.15 16.44 18.55 20.32
    19.0000 15.71 15.92 16.10 16.33 16.62 16.97 17.40 18.04 19.11 20.69
    19.7500 10 0
    19.7500 0.00 1.97 3.95 5.92 7.89 9.86 11.83 13.77 15.63 17.22
    19.7500 17.72 17.82 17.92 18.02 18.14 18.30 18.52 18.88 19.54 20.69
    20.0000 0 0
    20.0000 0.00
    20.0000 0.00
    82.04 312.09 184.36 218.46 338.79 404.75 396.38 604.55
    630.61 526.37 528.94 515.75 552.75 543.42 467.49 568.51
    518.97 392.2 237.12 233.9 195.62 24.77 0.0
    10.5
    1
    6 7.4564 13.1180 3.0000
    8.000 22.56 9.60 45.00000
    9.0000 23.20 7.12 45.0000
    10.0000 23.68 6.32 45.0000
    11.0000 23.04 6.08 45.0000
    12.0000 22.56 6.56 45.0000
    13.0000 21.44 7.28 45.0000
    1
    13.5000 16.5000 20.00000 0.0000 0.0000 0.0000 20.5000
    1
    19.2629 19.9022 10.1667 15.0625 15.0625
    19.4220 19.7600 10.1667 1.6458 1.6458
    1
    18.5425 18.6764 18.16 13.6 17.68
    18.5425 18.6764 13.52 3.68 3.68
    18.5425 18.6764 3.04 13.92 14.4
    0
    0
    0 0
    1 2.0 SIGNIFICANT
    10.
    STOP
     
  11. formsys
    Joined: May 2007
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    formsys formsys

    Seakeeper is good for predicting motions of barges and also can be used for catamarans (you have to set the vessel type in the Analysis menu), however I dont think strip theory methods like Seakeeper will give you good results for "L" shaped structures such as the one you show. A high end (high $) system like WAMIT etc would be needed.
     

  12. offshoreguy
    Joined: Aug 2009
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    offshoreguy Junior Member

    Leo, I think I hear you laughin from the other corner of the world!

    Formsys, it is not a "L" shape, it is a "T" shape.
    It is not a price problem, but time to learn a not suit package.

    I have made a sw package that is based on database as g=f(x,y,z) (I improvesd 15% existing sw used in concrete mixture results). It takes the place for every variable in the region where I have data. I could set into a lot of tank data. I only need coordinates of main points of hull parts, and place pressure sensors in a matrix, not only in ship surface but also in the water. I could take into modifications in the wave shape due the hull parts.
    My idea is to advise of new tank tests in areas far from existing data. It does not mind if waves are linear or not.
    Few maths=high prcesing speed and
    lots of tank data=low failure probability
     
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