Advice about obtaining Response Amplitude Operators

Hello,

I am looking to obtain some RAO's for 2 to 3 theoretical vessels. e.g. a work boat, a semi-sub and a tanker.

Obviously free public domain version would be ideal, but I have not been able to find any of these.

I have had a look for companies could generate and sell some RAOs, but it is hard for me even determine which companies would even offer this service.
There are a lot of companies that offer very complicated software packages that could generate the RAOs and a whole lot more, but purchasing and operating the software is way beyond me at this point in time.

As a last ditch effort I thought I would post here in the hopes that someone would be able to point me in the right direction of where I can find some RAOs, or where I could purchase some RAOs.


Thanks,

Simon

 

I am not myself an expert but I can suggest you 2 directions that I know serious. These are softwares, but once you have established a contact, maybe they can guide you to a service company that will calculate the RAOs from your design.

Free public domain : >>> NEMOH, by Ecole Centrale de Nantes researchers. You have just to register, before download the source. And there is a Forum to help you and answer your questions. Probably require a good level of expertise from your side ...
NEMOH-Presentation https://lheea.ec-nantes.fr/logiciels-et-brevets/nemoh-presentation-192863.kjsp?RH=1489593406974

Professional tool : >>> Hydrostar , by Bureau Veritas. If you, your Company or your University can buy a license...
Hydrostar software Powerful hydrodynamic solver https://marine-offshore.bureauveritas.com/hydrostar-software-powerful-hydrodynamic

 

Having been in this situation, where someone comes and asks me for RAO's, my first question is "Why do you want them"? RAO's improperly used can kill everyone on the vessel.

Since it seems that you do not have a definite need for a specific set of RAO's, estimate them yourself using the Lewis Factors, or write a panel model (it can be done in 30 lines of code).

 

Thanks so much for the links.

 

Very good question. Essentially I plan to do vessel motion simulation.
I have access to forecasted 2d wave spectra and have created a program that calculates vessel motion based off RAOs and 2d wave spectra.
The vessel motion software was tested against a set of RAOs, predicted motion (from another vessel motion simulation software), and against observations.

I can potentially gain access to vessel motion observations for additional vessels so I can run further comparisons. However, I cannot get the RAO's of the vessels themselves (protected IP etc)
Using the specific RAOS for the vessel would be ideal.. but failing that the plan would be to choose a set of RAOs that is most similar to the vessel in question and see how the observations and predicted motions compare.

 

Another link which can be helpful, this book by Prof. Journée and Massie, TU Delft, Seakeeping is Journée passion since long, in case of you have his email address in the book. In chapter 8.4, you have examples of typical RAO's for Oil Crude carrier, Aircraft carrier, Container carrier.
https://ocw.tudelft.nl/wp-content/uploads/OffshoreHydromechanics_Journee_Massie.pdf

 

<sigh> A forecast from a forecast of an estimate is worse than useless, as it is generally so far wrong that it becomes ignored when it needs to be looked at. The past is the past, NEVER to happen again. The future is so random as to be uncalculatable. The best you can do is what the US Navy has had access to for the past 20 years, which is the estimated maximum response using on platform sensors designed for that platform. Please do not proceeded this way without thinking about the desired outcome further.

 

I understand your scepticism, I am not committed one way or the other as to the usefulness of the final results.
"A forecast from a forecast of an estimate" is a nice way of putting it though, and certainly highlights the likelihood of a useful outcome.
Hopefully you can now see why I am looking for some open source options here..
The aim would be to compare it to observations and either confirm it is useless, or determine if there are any situations where some value can be achieved.

 

I actually used this book as a reference many times. I never thought of contacting them directly.. Good thinking!