PDStrip, free strip theory program

[Martijn_vE]

It's very new and open source.:)

Quote:

"PDSTRIP is a hydrodynamic strip code for seakeeping. It computes ship motions for monohulls including sailing boats."

You can download the program and the code from: http://sourceforge.net/project/showfiles.php?group_id=163390&package_id=184687&release_id=415626

I'll add an export function in FREE!ship later this week that creates the neccesary files.

[Raggi_Thor]

Sounds very interesting. Is it reasonable easy to use?

[Martijn_vE]

It has to be run from the command line. It uses two input files (one for settings such as wave height nd directions and the other containing the hull geometry. After execution it generates output files with the desired information. So it's easy to run :) , but preparing input and examining output would be a pain if done manually:( . I intend to implement both in FREE!ship, so you can run the program in the background.

[Raggi_Thor]

Martijn!
Thats great!
:-)

[Jaja]

i am actuaaly in a placement and my work is to compare results of pdstrip and other methods.
Actually i m reading theory on pdstrip but i am fighting to understand output files
Did your work on pdstrip and free!ship has results ?
can i have some files about it ?

I would be happy to help in the development of such tools... but it will take me a lot of time because i am discovering fortran as well as naval calculus (actually i have just a mechanical formation)

Thanks for reading
Jaja

[Martijn_vE]

I've finished implementing the procedure that creates the output files for PDStrip and starts the program from within FREE!ship. I'm also having trouble interpreting the output files, especially the responsefunctions file since I want to display them in FREE!hip. I asked for some clarification (at Ensieta) on the subject but haven't had any respone (yet). I can read Fortran pretty well but the ource is not transparent enough for me to understand exactly what info is written to the output files.

[Jaja]

In fact i am an ensieta student but i am actually working on pdstrip at insean in italy.
I suppose you are dealing directly with bertram ?
The problem is that the pdstrip specialist at insean will be back end if july so i have to find a solution just know.
i will e mail bertram about this but it could be nice to do some teamwork :)

Ajaj

[Martijn_vE]

Thanks Jaja.
Yes, I sent my question directly to Bertram. I hope he's able to answer it.
How is Insean involved in all this and what is your job over there?
Please look at my reply to your message at the FREE!ship forum regarding the subject.

[Tim B]

Looks like a good bit of software, and it has the advantage that it will run under any system. Win / Linux / MacOS anything.

Great work, let's hope for more like it,

Tim B.

[gaggio]

Hi everyone!
I write here because I also have problems while trying to read reasults of pdstrip...:confused:
I need response functions, but I really have no idea about the format used in the output file. The postscript guide of pdstrip is not helping much with that!
If somebody out there is able to explain me something, I will be very grateful, since I have really few days to get some data out of a simulation!
I attach here the output from the example included with the software, so that we can speak about a real case.
Example Yacht 1 testfile March 2006
0 F 9.81 1. 0.
5 9. 13.5 18. 24. 36. 1 0. 7 0. 0.5235984 1.0471967 1.570795 2.0943933 2.6179917 3.14159 19 -7.519818 -6.519845 -5.519858 -4.519868 -3.519875 -2.51988 -1.519883 -0.5198837 0.480117 1.480225 2.480225 3.480225 4.480225 5.480147 6.480157 7.480225 8.480225 9.480225 10.48021
0.004785021 0.00025021273 0.013166568 0.00021451511 0.0030213818 1.4439783E-7 0.0004883797 0.0027458249
0.003375657 0.0027943393 0.037080158 0.001339592 0.0021655217 0.000014063459 0.007362689 0.030664979
0.041518774 0.14888665 0.070647016 0.06867129 0.012970563 0.0015037598 0.39751902 1.6338763
0.00042621468 0.99189794 0.8881196 0.4621415 0.001089033 0.000103490296 2.6946063 10.88505
0.05722108 0.091781296 0.00016000938 0.06414578 0.024854438 0.0023820768 0.21264216 1.0072043
0.0010161388 0.002506576 0.013739337 0.0016569357 0.0011908406 0.00003006277 0.0056985538 0.027507065
0.0043959864 0.00030282285 0.001671803 0.00025953195 0.00343979 1.731435E-7 0.0005910429 0.0033231664
0.024313157 0.00010493146 0.031292044 0.00006544587 0.0038643612 1.16604824E-7 8.988924E-7 0.00036718213
0.06270289 0.02635015 0.043474585 0.005657303 0.011526315 0.00079038885 0.0045239893 0.09220595
0.1459456 0.49491057 0.45365325 0.10629538 0.02903647 0.0028125104 0.082223624 1.7318195
0.00038328543 1.1817572 1.0969284 0.24701941 0.0005538897 0.00005048354 0.21214232 4.1352725
0.17503636 0.40142095 0.21172753 0.09517144 0.044319835 0.0036715106 0.06940445 1.4046751
0.07546438 0.022472613 0.017597245 0.0061048195 0.01770236 0.000952221 0.003622947 0.07863745
0.02902564 0.00017484782 0.02998753 0.000109348206 0.005991781 1.9696E-7 0.0000014283062 0.00061183743
0.18080169 0.00032804365 0.091997996 0.00016246033 0.02165478 5.727593E-7 0.000009262264 0.00077420706
0.23042028 0.089366674 0.1882331 0.010700524 0.028025864 0.0013640311 0.0033624223 0.21091191
0.20080641 0.6343003 0.6808057 0.07719507 0.024644163 0.0026139251 0.02240794 1.4969953
0.00029265933 1.1590877 1.1062572 0.13718022 0.00026292042 0.000027013979 0.04554736 2.735532
0.22513917 0.56861484 0.5050717 0.07151168 0.0334515 0.0032013198 0.02324879 1.3419728
0.2564439 0.07695168 0.0995596 0.010042285 0.037369076 0.0015571009 0.0033134804 0.1816116
0.20296143 0.0004770124 0.044830874 0.00023670777 0.029339526 8.3560644E-7 0.000013546859 0.0011257841
0.4248364 0.0002164752 0.29214147 0.00008485143 0.030654227 6.519147E-7 0.000015952823 0.0003972456
0.41540197 0.15172623 0.42039135 0.0103279 0.029998027 0.0014004164 0.0014259273 0.27842718
0.22975864 0.7075407 0.82128036 0.048471145 0.01649507 0.001987464 0.0061992104 1.2983817
0.0002275123 1.1256634 1.0854588 0.0754153 0.00012319301 0.000014175664 0.010991064 2.065663
0.24629505 0.6702681 0.7300776 0.04619953 0.020473437 0.0023423187 0.0072624134 1.229984
0.44127816 0.13726918 0.3346115 0.009441607 0.036448117 0.0015587987 0.0016890169 0.2518976
0.45297578 0.00028972517 0.22270726 0.00011366055 0.037409794 8.6105166E-7 0.000021387375 0.0005316639
0.70852154 0.000024783085 0.6073256 0.000007671992 0.02335001 3.0308817E-7 0.000002962885 0.00003637103
0.5926267 0.20664471 0.70275164 0.0063263583 0.019483829 0.000961658 0.00033105933 0.30326664
0.24469486 0.7454062 0.93073136 0.022719385 0.00796199 0.0011229255 0.0010728894 1.0939394
0.00017749525 1.0769814 1.0567212 0.032349523 0.000045381254 0.0000047489093 0.0016074126 1.580551
0.2534842 0.73131156 0.90143347 0.022114828 0.00909483 0.0012456173 0.0012758492 1.0732545
0.6089166 0.19600722 0.6632994 0.005804027 0.021821287 0.001034525 0.00042472617 0.28765526
0.729548 0.000031941487 0.568017 0.000010033651 0.026153916 3.7739164E-7 0.0000038913427 0.000046876525


Thank you in advance! :)

[Jaja]

e mail me canard.leouf@laposte.net and i will give you file that i write about pdstrip result reading.

[gtampier]

Hi!
I'm able to read the results, but I get only x-y-z "displacements" (are those the same as RAOs if wave amplitude = 1 ?). I need also added mass and damping coeffs, so I can try to calculate added mean resistance. Has someone some experience about it?
I'm also experiencing problems when trying to calculate more than one sea state (last line(s) of input file), the program sends an error mssg. and does't calculate... maybe a bug? or does someone know any trick to solve this?
Thanx!

[Tim B]

No, I know there is an XYZ hullform output (which look very similar to the input). I do wonder if the result is the solution matrix, not the RAOs. I haven't got round to looking at it in any detail yet, but I will have to sort it out before Christmas.

Tim B.

[gtampier]

I have some good news. The Absolute terms (1, 2, 3) for translations and rotations are the 6 RAOs. I quote the user manual in p.10:
The absolute value of the complex amplitude is the (real) amplitude, also called response amplitude operator RAO. The ratio between imaginary and real part of the complex amplitude describes the phase shift between the response and the exiting wave
If you give as input different wave lengths you will get results for different encounter freqs. Here as example some results:

wave circ. frequency 1.700
encounter frequency 3.173
wave length 21.33
wave number 0.2946
wave angle 180.0
speed 5.00
wetted transom? T
log(determinant) 87.82 12.41
Real part(1) Imagin.part(1) Abs(1) Real part(2) Imagin.part(2) Abs(2) Real part(3) Imagin.part(3) Abs(3)
Translation -0.000 -0.011 0.011 -0.000 -0.000 0.000 0.100 -0.002 0.100
Rotation/k 0.000 -0.000 0.000 -0.000 -0.006 0.006 0.000 -0.000 0.000


I'm comparing results of PDSTRIP with SEAWAY and SEAKEEPER (Maxsurf), and for a box-shaped barge they seem OK. I'm calculating a containership now, I will tell you about the results later...

[Danimal]

wicked - that would be a great comparison - would you be at all interested in compiling the results in brief report format? it would be interesting to review

D

[ticotico]

Is there anybody who use PDStrip. I search the rel. vertical velocity of a motion point (like seakeeper can do this). Is it possible to calculate it with PDStrip?
Have anybody some example-files for the use of motion points (e.g. the sample from gtampier) or a good manual to read the result files or an GUI?

It is a nice program but you need many time to understand it and to use it.

[Aquilo]

I'm just trying to use the pdstrip program, which seam to be a good tool - provided that the result-files could be read.
Does anyone have a brief explanation for the output-files created by the pdstrip program?

[Martijn_vE]

PDStrip is very poorly supported.

[Aquilo]

never the less, my you have found out how the sectionresluts-file has to be read?

There are 9 complex added masses for 52 frequencies for every section.
Is it right that these values represents a 3x3 matrix with the y,z,xx (sway heave and roll) on the diagonal (respective 1st, 5th and 9th value)?
Do you know, if these values have to be multipied by a factor like t_ref?

Below the added mass data the diffraction forces and Froude-Kryloff-forces are stored for every angle.

so far....

[williamstewart]

Can anybody supply me with recent information regarding PDStrip?

I have been able to run the file with the PDSTRIP GUI (that you have to compile) available from Silversoft. However, the "responsefunctions" results files that should contain the RAO data is in a format that is ambiguous, giving 8 columns and 35 rows (8 x 35 = 280) or 280 numbers for the example problem. There are 4 wave attack angles and 5 wave length given in the input data. I would therefore expect 4 x 5 x 6 = 120 number "sets" for each of the 6-DOFs (at each heading and wave period). I would have hoped for an amplitude and phase pair of numbers in each "set", but possibly the three as descibed by gtampier, being thr real, imaginary and absolute. These two possibilities would give 240 or 360 numbers in the output, compared to the 280 I find.

Any help would be much appreciated.

I also would be interested to know if Martijn_vE has made (or may make) available his adaptations of FreeShip to link with PDStrip.

Kind regards to all, Bil. bil@stewart-usa.com.

[williamstewart]

PDStrip is very poorly supported.
Can you (Martijn) supply me with recent information regarding PDStrip?

I have been able to run the file with the PDSTRIP GUI (that you have to compile) available from Silversoft. However, the "responsefunctions" results files that should contain the RAO data is in a format that is ambiguous, giving 8 columns and 35 rows (8 x 35 = 280) or 280 numbers for the example problem. There are 4 wave attack angles and 5 wave length given in the input data. I would therefore expect 4 x 5 x 6 = 120 number "sets" for each of the 6-DOFs (at each heading and wave period). I would have hoped for an amplitude and phase pair of numbers in each "set", but possibly the three as descibed by gtampier, being thr real, imaginary and absolute. These two possibilities would give 240 or 360 numbers in the output, compared to the 280 I find.

Any help would be much appreciated.

I also would be interested to know if Martijn_vE has made (or may make) available his adaptations of FreeShip to link with PDStrip. It seems that DelftShip is a slightly modified version of FREEShip. Will there be a PDStrip link to/from DelftShip?

Kind regards to all, Bil. bil@stewart-usa.com.

[Paolo83]

Hello everyone! My name is Paul
I recently joined this forum, I'm looking for a program to calculate the RAOs functions. I need these functions to do the analysis on a single buoy moored vessel.
I think Pdstip can be the right program, but never having seen it. I have no idea how it works.

Does anyone know a manual?
I tried to make it run on Windows XP, but it gives me an error even though I have gfortran installed, someone can give me some help?

Thank you!

[daiquiri]

Does anyone know a manual?
I tried to make it run on Windows XP, but it gives me an error even though I have gfortran installed, someone can give me some help?
Citing from sourcefoge site (http://pdstrip.sourceforge.net/):
"PDSTRIP has been abandoned by its initiators, who do not wish to be contacted with use questions. The position of maintainer is vacant."

[Paolo83]

This does mean that there is no a open source seakeeping program?

[Leo Lazauskas]

This does mean that there is no a open source seakeeping program?

SMP - Ship Motion Program
See my post:
http://www.boatdesign.net/forums/design-software/softwares-dynamic-ship-analysis-12808.html

Good luck

[Paolo83]

Thanks it looks interesting.
Unfortunately the link that you put on the forum does not work and now VISUAL SMP is for sale.
The book is interesting but there are 200 pages of code to be copied by hand ...

[daiquiri]

The book is interesting but there are 200 pages of code to be copied by hand ...
But once you've done it with no errors, it you can sell the software and earn some money. ;)

[Paolo83]

This was not the idea -_-' ...but okay

Then turn the question, is there a theoretical reference for making "hand"this kind of calculation?
For "by hand " mean with matlab or similar programs.

Is enough for me an approximate solution, such as strip-theory by cutting the vessel in a few sections.

[Leo Lazauskas]

Thanks it looks interesting.
Unfortunately the link that you put on the forum does not work and now VISUAL SMP is for sale.
The book is interesting but there are 200 pages of code to be copied by hand ...

The source code was available a couple of years ago but it was difficult to find within the US Navy maze.

The theory for SMP is based on the very famous paper:
SALVESEN, N., TUCK, E.O. and FALTINSEN, O.
"Ship motions and sea loads", Transactions SNAME, New York, 78 (1970) pp. 250-287.

Good luck!
Leo.

[Tim B]

I have just e-mailed the current maintainers of PDStrip, requesting to take over the maintenance role. If they agree, this does not mean that there will be massive changes to the code immediately, but I will get the support mechanism to the same level as OpenPilot, and I will be inviting anyone with validation data to contribute it.

For now, we must wait to see what the current maintainers say.

Cheers,

Tim B.

[Paolo83]

I have just e-mailed the current maintainers of PDStrip, requesting to take over the maintenance role. If they agree, this does not mean that there will be massive changes to the code immediately, but I will get the support mechanism to the same level as OpenPilot, and I will be inviting anyone with validation data to contribute it.

For now, we must wait to see what the current maintainers say.

Cheers,

Tim B.


Ok! In this case, we hope for good :)

[Paolo83]

The source code was available a couple of years ago but it was difficult to find within the US Navy maze.

The theory for SMP is based on the very famous paper:
SALVESEN, N., TUCK, E.O. and FALTINSEN, O.
"Ship motions and sea loads", Transactions SNAME, New York, 78 (1970) pp. 250-287.

Good luck!
Leo.

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.

[Paolo83]

The source code was available a couple of years ago but it was difficult to find within the US Navy maze.

The theory for SMP is based on the very famous paper:
SALVESEN, N., TUCK, E.O. and FALTINSEN, O.
"Ship motions and sea loads", Transactions SNAME, New York, 78 (1970) pp. 250-287.

Good luck!
Leo.

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?

[Tim B]

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.

[yipster]

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

[Paolo83]

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.


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?

[Tim B]

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.

[Replica]

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

[Paolo83]

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.

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

[Tim B]

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.

[Paolo83]

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.

[Tim B]

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.

[Tim B]

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.

[waver]

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!

[Tim B]

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.

[CWTeebs]

I'm having trouble finding any documentation about the underlying theory. Is it similar to VisualSMP?

[Tim B]

The underlying theory for PD-Strip is well documented, and is available from the software repository. Here : http://opendynamics.cvs.sourceforge.net/viewvc/opendynamics/src/pdstrip/doc/pdstrip_documentation.ps?view=log

The thoery behind openDynamics is quite detailed for each individual component. Essentially, it is based on adding up all the forces at each point on the components, then moving the model accordingly. Each component will have it's own detailed theory, which will be described separately (for waves, foils, hull etc). openDynamics is not based on a strip-theory method. It is (primarily) a time-domain, volumetric method.

In conclusion, pdStrip is similar to VisualSMP (just without most of the visual at the moment), and openDynamics isn't at all similar.

Hope this helps,

Tim B.

[imita_seixo]

Dear Gtampier:

I found your post really interesting. Do you have the geometry and results for this barge? We are having problems matching a similar case with both codes.

Sincerely.

Antonio



I have some good news. The Absolute terms (1, 2, 3) for translations and rotations are the 6 RAOs. I quote the user manual in p.10:

If you give as input different wave lengths you will get results for different encounter freqs. Here as example some results:

wave circ. frequency 1.700
encounter frequency 3.173
wave length 21.33
wave number 0.2946
wave angle 180.0
speed 5.00
wetted transom? T
log(determinant) 87.82 12.41
Real part(1) Imagin.part(1) Abs(1) Real part(2) Imagin.part(2) Abs(2) Real part(3) Imagin.part(3) Abs(3)
Translation -0.000 -0.011 0.011 -0.000 -0.000 0.000 0.100 -0.002 0.100
Rotation/k 0.000 -0.000 0.000 -0.000 -0.006 0.006 0.000 -0.000 0.000


I'm comparing results of PDSTRIP with SEAWAY and SEAKEEPER (Maxsurf), and for a box-shaped barge they seem OK. I'm calculating a containership now, I will tell you about the results later...