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/showf...ease_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...
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