Cfd

[Steve Hollister]

The details of CFD for vessels are so complicated that I don't think it is advisable to try and understand much unless you spend some time with the technical papers. Unfortunately, I don't know of any papers that approach the material on an introductory basis. The best one that I know of (that I mentioned before) is geared to naval architects - in fact it was just presented at the recent annual meeting of SNAME. It is located at this web site, along with the other papers presented at the conference. If you want the paper, you better grab it, because I don't know how long it will be available on-line.

"Modern Computational Methods for Ships in a Seaway", by Beck and Reed
http://www.sname.org/AM2001/2001_technical.htm

For those willing to dig in, this paper brings you right up to date on all of the CFD applications applied to vessel motions and resistance. The best parts are an historical review of the codes and theories, and a complete taxonomic breakdown of hydrodynamics problems for seakeeping. The main breakdown is between the invicid flow theories (potential flow) and the viscous flow theories (Stokes, RANS, LES, etc.). At the very least, if you read this paper, you will be up on all of the lingo!

I am willing to write output meshing routines from ProSurf to go to these CFD programs, but I don't know if there are any CFD programs (with free surface calculation) available at low or no cost.

 

[turnershells]

I was lucky enough to have a fourth year engineering student from Limerick, Ireland contact me last year about using my hull for his fourth year CFD project. He used Fluent and a dxf file of mine that's about 1.2meg, but he had to translate through another program first.
Some incredibly nice graphics came out of it, and I'll try to post the best as an attachment. I found it very useful, even though the design and mould were finished.

 

[Pioneer]

Hi! to all.
I'm new in this forum.
I'm trying to use Fluent to progect some kite and similar.
My problem is to traslate the DXF file for fluent , how do you do it?

Thanks to all

 

[hardy]

Hi,

do you have a 3D model of a single hull fast RoPax Ferry?

thanks,



hardy

 

[fireball]

Hi,

This is a very interesting thread you have started here. Gades, as far as freeware CFD the only software that I have used that a free download is available is WAMIT, which is a software written by MIT for analysing wave interactions between floating/submerged structures and waves.

I have been involved in some research with SHIPFLOW software, and its reliability for predicting resistance performance for vessels. I have undertaken an analaysis of a systematic analysis of catamaran configurations and compared this to experimental data compiled by Molland et al from the early 90's.

The results were validated using the experimental data, however I undertstand that this is very hit and miss. Generally from my experience, the value of CFD lies in it's ability to compare several different hull forms or prototypes (whatever you are analysing). Therefore the precision of any analyses becomes important and not their accuracy.

Often CFD is used for finding a comparison between several models, and then this data is scaled according to some experimental or full scale data to make the results useful.

Anyways, WAMIT is quite a useful software that produces quite reasonable results, however it application to vessels in somewhat limited as I think it was intended for use by stationary structures encountering a uniform stream.

The most advanced software packages available would definately be provided by the aeronautical industry in the US of A. Although some of the theory is different (compressible air as opposed to incompressible water) there are many good websites which some appropriate theory.

 

[Stephen Ditmore]

Hardy:

The only applicable public domain hull lines I know of are published as part of U.S. Patent 5832856
http://www.delphion.com/details?pn=US05832856__
http://patft.uspto.gov/netacgi/nph-...0&s1=5832856.WKU.&OS=PN/5832856&RS=PN/5832856
(and in David Giles' prior patents, which are referenced by this one). I think Giles' claims are specific to vessels over 200 ft, leaving you free to use his hull shape for vessels under that length (61 meters).

For more on this vessel see http://www.fastshipatlantic.com/innovativeshipdesign.html

For a trade publication see:
http://www.fastferryinfo.com/default.asp

For builders of monohull fast ferries see:
http://www.marine.alstom.com/servle...duct_type&cid=1006515717559&rid=1006332189529
http://www.izar.es/english/homeIng.htm
http://www.fincantieri.com

 

[Angelo D'Ettore]

other cfd software for free surface evaluation

for investigating the hydrodynamic properties of Hull have a look
www.shipworks.it

session "step to step"

Angelo D'Ettore

 

[julleras]

Michelet page

Michelet is on page http://www.cyberiad.net/michlet.htm.