Which software can I use for wave patterns?

[sizzurp]

I want to compare some hull forms with respect to wave patterns and resistance. Froude number +/- 0.4. Which computer program can i use best?

(made the hullforms in rhino)

many thanks!

[Ad Hoc]

the wave patterns will all be the same, the resistance will be different when the hull forms are different, ie length displacement ratio's etc.....not sure what your question is?

[sizzurp]

I have to do a study: fast ships and wash.

The waves are not the same for every hull form, i.e. catamarans produce different waves (different angles) than monohulls.

I know there are (potential theory) programs like RAPID and SPLASH, but are there also free programs? (or low cost)

[Martijn_vE]

Michlet http://www.cyberiad.net/wake.htm

[Ad Hoc]

"..The waves are not the same for every hull form.."

This just shows that your level of understanding on the subject is very low and that need to read a lot more about hydrodynamics first before you start playing with computers and what they 'show'. Suggested reading:
"Basic Ship Theory" - Rawson & Tupper
"Hydrodynamics in Ship Design" - SNAME Publication.

[Rick Willoughby]

I have to do a study: fast ships and wash.

The waves are not the same for every hull form, i.e. catamarans produce different waves (different angles) than monohulls.

I know there are (potential theory) programs like RAPID and SPLASH, but are there also free programs? (or low cost)

Michlet is no longer supported on the cyberiad site. You should be able to download from this link:
http://www.boatdesign.net/forums/attachments/design-software/32766d1246040007-michlet-godzilla-availability-mlt807.zip

It does not have a flashy GUI but I expect it will give you reliable results once you learn how to drive it. It is impressively fast.

Rick W

[sizzurp]

Thanks Rick!

And ad hoc, are you saying that every ship produces the same waves?
It shows that your level is stuck at basic ship theory..
read for instance: http://www.cyberiad.net/library/pdf/tsl02b.pdf

[Ad Hoc]

sizzurp
"..hull forms with respect to wave patterns .."

Then i think you need to understand the terminology of wave patterns or define yourself more clearly.

Since it appears you are talking about wave energies and their amplitudes, rather than a wave pattern. A pattern, as the word suggest, is a repeating process. Waves produced by a moving body in water produces repeating patterns, as shown in the diagram in post#3, .
http://www.boatdesign.net/forums/boat-design/wave-pattern-question-28667.html

Hence your understanding of the term "wave patters" per se, is not correct.

[sizzurp]

They often call it wave patterns in literature, so yes energy, amplitude and propagation direction. I thought all together defined as "wave pattern". Just want to do a little study before my real work begins.
Sorry I called you a noob, just miscommunication I guess.

[Ad Hoc]

sizzurp
That is because those that write these often very detailed and complex papers, are not naval architects, they are generally mathematicians. (they use a slightly different nomenclature). They are looking at the wave surface from a pressure distribution/energy point of view. Terribly fascinating stuff, but, no real use to the practical naval architect. (though their work many years later is of great use, once validated and can be used on a daily basis..)

Hence, wave patterns, as naval architects define them, are based upon the observations from Lord Kelvin, and since defined as such ie looking down on the boat in plan view, not a cut through the water.

I assumed your definitions may be a little off, hence the clarification, since English may not be your native language. No biggy...just dont jump to conclusions, if in doubt, ask!

[sizzurp]

lol, you said:
"your level of understanding on the subject is very low" , bit insulting for a phd-student..

But maybe i should have called it wash instead of wave pattern..

[Ad Hoc]

sizzurp

a phd of what subject?......without clarification, just as in your original question, any and all conclusions may be drawn; could be a phd in 'flower arranging', without context, what does it mean?. Being a student or having a phd, doesn't mean one should or does know everything on the subject at hand.

Asking questions and exploring ideas/logic and theory educates us. But cold assumptions do not. That is the mistake made by many poeple who use and rely far to heavily on computer software for their answers. The answers to the questions they should seek, are from books and other verifiable sources, not a series of 1's and 0's that have very prescriptive set of limits, which many choose to ignore or simply do not understand. A pretty pictures may help you 'see' things better, but it does not in anyway make you understand the how's and the why's.

[sizzurp]

I'm a naval architect, studied hydromechanics with a lot of mathematics. subject: low wash fast ferries.
My question is just if there's any software to calculate wave patterns. I think that's pretty clear for people who know what i'm talking about. end of discussion.

[Leo Lazauskas]

They often call it wave patterns in literature, so yes energy, amplitude and propagation direction. I thought all together defined as "wave pattern". Just want to do a little study before my real work begins.
.

I recommend a very interesting recent paper:

"Bank erosion from small craft wave wake in sheltered waterways",
Macfarlane, G.J., Cox, G. and Bradbury, J.
Int. J. of Small Craft Technology,
2008, RINA,

The authors dispel a few myths regarding wave wakes and erosion, and they make a strong argument against simple single criterion measures of the potential damaging effects of wave wakes, e.g. (among others) maximal wave height. They also make a fairly strong argument for using wave energy per unit wave height (units LT^2) and the wave period of the "maximal wave" as useful descriptors.


Best of luck with your studies!
Leo.

[sizzurp]

That's a very interesting paper, thank you very much! Have seen your name very often while searching the internet for articles.

[Ad Hoc]

sizzurp
"..My question is just if there's any software to calculate wave patterns.."
There are plenty about (for the type you are looking for), but are they accurate, is a totally different matter. That comes down to the how's and why's, not the pretty pictures.

There has also been a lot of work done by the MCA in the UK on wash and also by Whittaker et al, Dand et al, and Kofoed-Hansen et al.

You may find the attached of interest, not widely obtained. These are generally more for the "mathematically" minded that do research in that field.

[sizzurp]

For now, it don't have to be very accurate. I don't need to know the exact height of waves, just want to compare some hulls. It's just a little research before I start.

And thanks for the recommendations.

[Ad Hoc]

sizzurp
I'm confused. If you're not worried about the accuracy, what difference does it make which software you use? Without any kind of validation, the answers you're going to get, as a sensitivity analysis, will be no better than any other software, and just as inaccurate as each other.

It is somewhat akin to using a saw, to hammer in a nail...you can do it, but not very well...and not every nail consistently, nor easily.

Just questioning your rationale in using a method that is not consistently accurate for all applications (non of them are), for comparisons, doesn't make sense. From a research, phd, perspective, but from a layman's perspective, it is fine...

[sizzurp]

I meant: I don't need to know (for example) the exact wave height on a mm.. I just want an easy in use software for my first calculations. And not a program were I need to know every little detail for the input.

[Leo Lazauskas]

I meant: I don't need to know (for example) the exact wave height on a mm.. I just want an easy in use software for my first calculations. And not a program were I need to know every little detail for the input.

Michlet will allow you to quickly compare simple hullforms like a Wigley or a parabolic strut. You can also see (far-field) wave patterns of multihulls with up to five demihulls. See the example section in the documentation of simple cases for catamarans and SWATH, trimarans, tetrahulls, SLICE, and pentamarans.

[Leo Lazauskas]

And a little more reading material for you...

I know you aren't specifically interested in the resistance aspects, but check out some of the high form factors in the paper by Molland et al. 1.47 for a catamaran!

[yipster]

and to hear another why not this extra book by Odd M Faltinsen Hydrodynamics of high-speed marine vehicles (http://books.google.com/books?id=Rv4Iep_NTAUC&pg=PA126&lpg=PA126&dq=Supercritical+wave+patterns&source=bl&ots=Hjbdrc4JJQ&sig=2fULumYGWiKjgkOfiTSFbSwLDOI&hl=en&ei=BrS7SsfnMpPh-Qat66DRCw&sa=X&oi=book_result&ct=result&resnum=9#v=onepage&q=Supercritical%20wave%20patterns&f=false)

[formsys]

The Hullspeed module in the Maxsurf suite of software uses a slender body method to calculate wake waves and resistance for slender hull forms.
http://www.formsys.com/maxsurf/msproducts/hullspeed
The attached picture gives an example of its output.
There are more technical details in the Hullspeed user manual in the download section of the FormSys web site.