Hull optimization

Discussion in 'Hydrodynamics and Aerodynamics' started by Alfonso, Jun 1, 2011.

  1. Alfonso
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    Alfonso Junior Member

    Regards,

    I'm interested in hull optimization regarding resistance, hydrodynamics in general or seakeeping. Can anyone write more about the subject, or recomend some literature??

    Thanks in advance?
     
  2. daiquiri
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    daiquiri Engineering and Design

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  3. Leo Lazauskas
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    Leo Lazauskas Senior Member

    Me too. :)

    Start with Daiquiri's suggestion.
    Also read the thread "Hull Asymmetry and Minimum Wave Drag" in this sub-forum to see what a difficult field it is.

    You can also play around with the free code "Michlet" to see how theoretical optima and trends can be found for thin-ships.

    Leo.
     
  4. Alfonso
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    Alfonso Junior Member

    I know it is a broad question :-D, and I am well aware that it is a difficult field.

    Maybe the question itself is kind of stupid, because, as Daquiri said ''It summarizes centuries of efforts in naval architecture in just one phrase.''

    But still, any literature is welcome and thank You for replying!

    Cheers
     
  5. gonzo
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    gonzo Senior Member

    When you optimize for one of the parameters you ask about, you lose on some of the others. At the end, a designer finds a reasonable compromise.
     
  6. Leo Lazauskas
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    Leo Lazauskas Senior Member

    That's why it is important to allow lots of constraints in any computer optimisation programs.
    Putting bounds on the possible solutions at least should give something close to practical. Without them you can end up with low wave drag hulls like Ward's Optimum Symmetric Ship.
    http://www.boatdesign.net/forums/at...al-displacement-hull-shape-min-drag-fig30.jpg

    What do you think of them, Alfonso? Is that what you want to end up building? :)
     
  7. NoEyeDeer
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    NoEyeDeer Senior Member

    Ok, I have to ask: since that appears (from the limited view available in the pic) to be largely normal but with a rather extreme bulb bow and the odd lump or two elsewhere, why couldn't it be built as a useful hull?
     
  8. Alfonso
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    Alfonso Junior Member

    Leo! That's it! :-D

    Just joking! HAHA! I have never seen this hulls! I understand the problem of using too little constraints, or using constraints that can't always be applied.

    GONZO,

    ''When you optimize for one of the parameters you ask about, you lose on some of the others. At the end, a designer finds a reasonable compromise.'' I completely agree with this!

    GONZO, I also want to thank You for Your help with my masters thesis!

    I repeat, I know that the thread is very broad, but do You have any papers regarding any specific case of optimization? Just to read and to study.
     
  9. Alfonso
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    Alfonso Junior Member

    Hm... Leo's point was that who ever did this, wanted only to minimize wave drag. From the first view at the pictures, I'd say that friction resistance is almost certainly greater that it should be. I could be avoided using wetted surface as a constraint I think... Also, there is a question of stability of such hulls, manouverability also, large bulb with width exceeding the breadth of the ship.... The middle hull is :confused::confused:!!!!

    Tipical example of what Gonzo said! You can optimize for one goal, but You must use a lot of constraints. Otherwise You get hulls like above....
     
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  10. Leo Lazauskas
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    Leo Lazauskas Senior Member

    "Diamond Tetrahull"
    http://www.cyberiad.net/waketet.htm

    Hovercraft
    Free-surface pressure distributions with minimum wave resistance
    E.O. Tuck and L. Lazauskas, ANZIAM Journal, Vol. 43, 2001.
    http://www.cyberiad.net/library/pdf/tl01.pdf

    Multihulls
    Optimum spacing of a family of multihulls
    E.O. Tuck and L. Lazauskas, Schiffstechnik, Vol. 45, No. 4, Oct 1998, pp. 180-195.

    SES and Multihulls
    Hydrodynamics of advanced high-speed sealift vessels
    L. Lazauskas, MSc Thesis, Applied Mathematics, The University of Adelaide, April 2005.
    http://digital.library.adelaide.edu.au/dspace/handle/2440/37729

    Unconstrained ships of minimum total drag
    E.O Tuck and L. Lazauskas, Dept. Applied Mathematics Technical Report, The University of Adelaide, Dec. 1996.
    http://www.cyberiad.net/library/multihulls/multipep/multipep.htm
     
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  11. BeppeZena
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    BeppeZena New Member

    Hi Alfonso & hi everybody,
    I'm new in the forum and this is my first post wow!.
    I would suggest you to start with the Principle of Naval Architecture (SNAME), just to see the main parameters involved in the problem.
    I found very useful the FRIENDSHIP website (link: http://www.friendship-systems.com/applications/papers ). Here you can find parers with some case study.

    hope that it is useful
    Beppe
     
  12. rxcomposite
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    rxcomposite Senior Member

    Alfonso,

    Start first by specifying The ship/boat Statement of Requirements 1. (SOR) then
    2. Work out the proportions
    3. Draw the lines
    4. Analize the hydrostatics
    5. Work out the freeboard and subdivisions
    6. Make the general arrangements
    7. Proportion the structural arrangement
    8. Estimate the Powering
    9. Do the preliminary weight estimate
    10. Work out the capacities
    11. Check preliminary stabilty
    12. Make a cost estimate.

    This is called design spiral and you cannot go directly to resistance, hydrodynamics, seakeeping, etc.

    While you are working out the stages, refer to Principles of Naval Architecture (3 volumes) and other relevant Naval Architecture books such as Powering, Hydrostatics, etc. Familiarize yourself also with Class Rules so you would be comfortable at the constraints. At the same time learn manual drafting or ACAD.

    After about 2 years, you will be able to go to the item 1 and start all over again tightening the design spiral. This is called optimization.
     
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  13. Alfonso
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    Alfonso Junior Member

    Beppe, thank You! It is useful.

    Rccomposite, thank You. I am a Naval Architect, so I know what design spiral is. I'm waiting for job or PhD so I only wanted to learn more reading the papers you recommend and by talking to you all in the mean time. Also, a design spiral is only one, and I think most general type of optimization in naval architecture. Maybe the most important.

    Leo, thank You, You did some excellent work and the papers are more than interesting. I only had a quick glance, but I like what I saw!!!
     
  14. BYDE
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    BYDE Junior Member

    Alfonso, I attach two recent publications that should give you a fairly good idea of modern hull optimization
     

    Attached Files:

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  15. rxcomposite
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    rxcomposite Senior Member

    Now that you have mentioned it, you are way past standard textbook materials. Paper about Design Spiral by S Hollister of New Wave can be downloaded from the net. The book Practical Ship Design by D.G.M. Watson will help you prepare for shipyard works. The book covers not only new construction but applies to ship modification as well.

    For Hydrodynamics, this is a very broad subject and many papers have been written about small craft, displacement and semi displacement, fast ferries and ships, bulbous bows, thin ships, multihulls, and other hull forms. You have to narrow down your interest and methods as approaches are sometimes traditional, CFD, or wave analysis. For example, Hydrodynamic optimization of ship hull forms by Applied Ocean Research is about CFD and bulbous bow.

    For preparation for PhD studies, I find the scholarly work of Leo and others in their library Cyberiad contains a wealth of topics.
     
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