PDStrip, free strip theory program

Ok! In this case, we hope for good

 

Thank you very much!
Because I am not a marine engineer did not know it, I found it on internet and it seems very interesting.
I read it and then let you know what I do think.

 

Hello!

I read the paper that you recommended to me. I've seen how it develops the theory of motion of the ship.
The paper recommended three different methods to determine the added mass matrix, damping matrix etc.:

1 - The Lewis-form method;
2 - The Tasai-Porter close-fit mapping method;
3 - The Frank close-fit source-distribution method.

Can anyone tell me where can I find the explanation of these methods?

 

Ladies and gentlemen,

I just thought I'd let you know, that I am forking pdStrip. The new fork will be called openDynamics. This is intended to be a community project, so please feel free to submit code to the repository when it is up and running (when sourceforge has recovered). There are two main points of contact for this project:

The Wiki - http://opendynamics.engineering.selfip.org
The mailing list - https://lists.sourceforge.net/lists/listinfo/opendynamics-community

I will be extracting info from this thread and implanting it in the wiki for future reference. Initially, the pdstrip code will not change (until I have time to do something with it), but the above links should be a good source of information.

If anybody has comparisons of pdStrip results with other software (which they don't mind being common knowledge) I'd like to be able to post them as validation evidence.

Cheers all, and thanks to the maintainers of pdStrip.

Tim B.

 

dear sir, meanwhile i have that free adroid smartphone helicopter applet but still have to buy the heli ;-$
on opendynamics do i understand its a flowlines program -attached a sample- as used by Martijn in freeship or more a stability program, some PD strip pics perhaps?
in the past i try'd PDstrip but didnt get any further as a dos error.. so dont know what i'm talking about and no help with fortran
or C++ from here but think i like to learn more on dynamics and signed up on the sourgeforce list

 

Hello!
This is very interesting!
I installed PDSTRIP. OpenDynamics (pdstrip still no change) can be downloaded?

Do you know give me a help to understand how to read the pdstrip's output file?

 

openDynamics is a fork of pDStrip. I haven't actually done anything with the code yet (and it'll be a little while before I do), but the wiki is up and running, so any info that you could post there would be helpful to others, I'm sure. There is an outline to reading pdStrip's output files a few pages back, the same is on the wiki. I haven't yet written anything about actually using RAOs, but I suspect most of us already know enough about that if we are trying to use the code anyway.

Cheers,

Tim B.

 

PDSTRIPGIU.f95

Sadly, the author of pdstripgui.f95, Gerrie Thiart, passed away last year.
Prof Thiart was a lecturer at Stellenbosch University, South Africa. He did a lot of work in the CFD arena

 

I played a little with pdstrip and I have put my results, consideration and question in the following link:

http://opendynamics.engineering.selfip.org/bin/view.pl/Main/PDstripSpectra

cheers

 

Paolo,

You can use the "attach" option on the wiki to provide input files. I have had a look at your input, and there seem to be a number of deviations from the format of the examples. Check this carefully, as it will make a difference.

Also, if you'd like anyone to asses and give you useful information, then we'll need a copy of the offsets file.

I will see if I have any generic hull-forms to get an example from tonight.

Cheers,

Tim B.

 

ok thanks!
I have attached input and output files (the vessel is the same on the example).
Compared to the example I removed the sails and suspended weight and I tried to include the spectral data.

 

Thanks for posting those files. The input is ok, but there is clearly a problem with calculating responses in a seaway. Typically, you would do this based on the RAO and the sea-state in a separate piece of code. As I remember it's not that hard. You need to produce the response spectra, calculate m0, then derive the RMS motions from that. There is more information on this in the documentation on page 30.

The results from your input look sensible. You would expect the response to approach 1 as you get to long wave-lengths. Where the documentation discusses RAOs, I believe that this is the acceleration RAO, based on the equation of motion on page 10. Usually, the acceleration RAO is the one of interest, though it should be noted that there are also position and velocity RAOs.

 

An update on openDynamics:

Sourceforge have got their CVS servers running again, so I have uploaded the latest version of the code to the repository. I have not done anything to the pdstrip solver, except to improve the build mechanism so it fits with the rest of the project.

I have, however, written a small utility which produces a set of offsets from a pdstrip sections file. It would not be hard to do the same thing in reverse. I have also updated the wiki with instructions for building and installing the code on Linux. This should not be hard to tweak for installation on MS Windows.

If you wish to develop code and commit it to the repository, you will need to be a member of sourceforge. Any new code should be written in C++ and use the QT4 libraries and build system as appropriate. This is a well proven system which will make life very easy later on.

Cheers,

Tim B.

 

PDSTRIP postprocessing

Hi.

What we got is all what we get. May be we can forward trying to get results with PDSTRIP.

I have compiled PdStripGui.exe and ran example. In "responsefunctions" we get 5 wavelenghts times 7 wave encounter angles what brings to a total of 35 records that seem to be the following 35 lines.

Each of these lines contains 8 data that I cannot understand. I expected 6 (absolute values for each Degree Of Freedom) or 12 (absolute values and phase angles).

Moreover: If I set a different number of encounter angles I get no results. have tried:

1 90
2 0 90
3 0 45 90
4 0 30 60 90 (This is the only combination that works).
5 0 22.5 45 67.5 90
6 0 15 30 45 60 75 90

Any idea?

Don´t give up. World is for pursuers!

 

Ladies and Gentlemen,

The software design for the openDynamics non-linear time-domain solver has
been released. It is available on the Wiki here :
http://opendynamics.engineering.selfip.org/bin/view.pl/Main/SoftwareDocs

Hopefully the base-code will follow in the next few months, but I am still
quite busy at present.

Cheers,

Tim B.