Australian Naval Architect May 2015

The May 2015 edition was released online today.
http://www.rina.org.uk/hres/The ANA Vol 19 No 2 May 15.pdf

 

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.

 

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.

 

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.

 

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

 

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

 

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

 

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.