Issue connecting lines with rods - moordyn-C v2.7.1

[amais29]

Hello,
I am trying to reproduce the dynamic cable case shown in article "Implementation and Verification of Cable Bending Stiffness in MoorDyn" (IOWTC2020, M. Hall et al.), section "dynamic cable scenario". The connection between lines and rods, to connect heavy and buoyant cable lengths, generates error. I am defining the model from a MoorDyn V2 input file.

The problem is on the creation of line end connections, during file load.
Actually, line "self.lineList.append( Line(self, num, lUnstr, lineType, nSegs=nSegs, attachments = [int(entries[2]), int(entries[3])]) )" in 'system.py>load' does not appear to be able to deal with non-numeric entries as for 'AttachA' and 'AttachB' fields. But to connect the B-end of my line '2' with the A-end of my rod '1', I need to write 'R1A' in line 2 'AttachB' field, as far as I know. I looked around a bit, and could not figure out a way to go round the problem easily.

The 'Lines' part of my input file looks like :

---------------------- LINES -----------------------------------------------
ID   LineType   AttachA   AttachB   UnstrLen   NumSegs   LineOutputs
(#)  (name)     (#)       (#)       (m)        (-)       (-)
1    lineOffset 1         2         27.45      55        pvt
2    Cable      2         R1A       34.3       70        pvt

Below is the error traceback :

---------------------------------------------------------------------------
ValueError                                Traceback (most recent call last)
Cell In[2], line 2
      1 import moorpy as mp
----> 2 ms = mp.System(file='filename.txt', Fortran=False)
      4 ms.initialize()
      5 ms.solveEquilibrium()

File (***)\anaconda3\envs\moor\Lib\site-packages\moorpy\system.py:124, in System.__init__(self, file, dirname, rootname, depth, rho, g, qs, Fortran, lineProps, pointProps, **kwargs)
    122 # read in data from an input file if a filename was provided
    123 if len(file) > 0:
--> 124     self.load(file)
    125     # check if bathymetry, if so sink anchors as needed
    126     if 'bathymetry' in kwargs:

File (***)\anaconda3\envs\moor\Lib\site-packages\moorpy\system.py:895, in System.load(self, filename, clear)
    893 
    894 #lineList.append( Line(dirName, num, lUnstr, dia, nSegs) )
--> 895 self.lineList.append( Line(self, num, lUnstr, lineType, nSegs=nSegs, attachments = [int(entries[2]), int(entries[3])]) )
    897 # attach end A
    898 numA = int("".join(filter(str.isdigit, entries[2])))  # get number from the attachA string

ValueError: invalid literal for int() with base 10: 'R1A'

Am I doing something wrong ?

Antoine

[mattEhall]

Hi Antoine,
The error is coming in MoorPy rather than MoorDyn. I'm not familiar with how MoorPy is used in your workflow. MoorPy doesn't have support for Rods yet. You could avoid the issue by avoiding using MoorPy. Also feel free to raise this as an issue in the MoorPy repo, to help flag this is a development task.
Matt

[amais29]

Hi, thanks for the answer, and sorry for the confusion. I will get rid of MoorPy. By the way, I tried to reach out to you at your NLR email address, but have been redirected. Do you know if it is possible to download, from somewhere, the input file of the model introduced in the article "Implementation and Verification of Cable Bending Stiffness in MoorDyn" (IOWTC2020), and presented in the "Dynamic Cable Scenario" section ? It could help in the definition of my base case, which is very similar and generic.

Thank you,
Antoine