Australian Naval Architect May 2015

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

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Leo LazauskasSenior Member

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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.

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Remmlingerengineer

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.

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Leo LazauskasSenior 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.

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Remmlingerengineer

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

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Leo LazauskasSenior Member

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

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Remmlingerengineer

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

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