Australian Naval Architect May 2015

Discussion in 'Education' started by Leo Lazauskas, May 13, 2015.

  1. Leo Lazauskas
    Joined: Jan 2002
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    Location: Adelaide, South Australia

    Leo Lazauskas Senior Member

  2. Doug Lord
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    Doug Lord Flight Ready

    Thanks Leo! Some very interesting stuff especially the detailed article on the DSS foil installation on Wild Oats XI and the "T" bulb discussion-and I'm not through yet.
     
  3. Remmlinger
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    Remmlinger engineer

    The resistance prediction by Fagerli for a trimaran and of course his regression analysis are interesting for me. Do you have an idea if the thin-ship method in the Maxsurf-code is identical to Michlet?
    When I compared Michlet to tank data, the measured resistance at FN=0.3 was always lower than the Michlet-prediction. Fagerli found the opposite. His measured value is higher than the thin-ship estimate. I am wondering what the reason might be.
     
  4. Leo Lazauskas
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    Leo Lazauskas Senior Member

    I haven't read it in any detail, Uli, because I have moved onto other
    (non-hydro) projects.

    One reason Michlet might predict higher resistance is that Michlet includes
    BL displacement effects unless you use a negative value for Ntheta.

    Maxsurf uses similar algorithms for predicting wave resistance. The last
    Maxsurf manual I read (about 7 years ago) mentioned that they use Filon
    transforms developed by E.O. Tuck. Those transforms for the z-wise integrals
    are exact for piece-wise linear sections: Michlet and Flotilla use Filon
    transforms that are exact for piece-wise parabolic sections.
    Michlet, Flotilla and Maxsurf use Filon transforms for the x-wise integrals that
    are exact for piece-wise parabolic waterlines. I believe Maxsurf is still using
    those numerical techniques.
     
  5. Remmlinger
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    Remmlinger engineer

    Thanks Leo for the insight you gave.
    Can non-hydro projects be fun? Hope they are not too simple.
     
  6. Leo Lazauskas
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    Leo Lazauskas Senior Member

    Quadrature of highly oscillatory integrals is nice clean applied maths, with exact answers guided by theorems and lemmas. :)
     
  7. Remmlinger
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    Remmlinger engineer

    Math is such a straightforward science. Compared to that engineering is a mess, but it seems that I like it messy ;)
     

  8. Leo Lazauskas
    Joined: Jan 2002
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    Location: Adelaide, South Australia

    Leo Lazauskas Senior Member

    I need to do some mathematics so I can speed up messy hydrodynamics
    problems. Also, multiple processors are now commonly available so I thought I
    would devote some time to re-code a few of my programs.
    That's the nice part of being retired/unemployed - plenty of time and no
    responsibilities. :)
     
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