Error when extract mooring stiffness matrix

[WTurbine]

Dear all,

I’m not familiar with pyMAP, and when I hope to extract mooring stiffness matrix through Ex3_StiffnessMatrixFromFST.py. However a question happends as shown below

Part from Ex3_StiffnessMatrixFromFST.py
fstFilename = os.path.join(scriptDir, 'spar\Main.fst')
print(fstFilename)
# moor = pyMAP()
moor = pyMAP(fstFilename)

error line: moor = pyMAP(fstFilename)
TypeError: pyMAP.init() takes 1 positional argument but 2 were given

And I check the pymap.py file as shown below and it seems that the init( self ) command needs none argument which obeys the code “moor = pyMAP(fstFilename)”. Could anyone tell me how to solve this?

Part from pymap.py
class pyMAP(object):

def __init__( self ) :
    self.ierr = c_int(0)
    self.status = create_string_buffer(1024)
    print(self.ierr)
    print(self.status)

    self.f_type_d       = self.CreateDataState()
    self.f_type_u       = self.CreateInputState( )
    self.f_type_x       = self.CreateContinuousState( )

What have to be noted are that I failed to create wisdem-env through the “mamba create env” command, so I use the “pip install wisdem” and “python setup.py develop” in the base environment and then run Ex3_StiffnessMatrixFromFST.py.

[gbarter]

There hasn't been much activity in pyMAP in a while because there has been less use of MAP as it was dropped from WISDEM and a secondary option in OpenFAST. I see there was a bit more activity in the dev branch compared to master. I would suggest giving that a try first.

[WTurbine]

Thank you for your comment and it really works. I have another question. The coordinate of the point in the code as shown below should be (0,0,+70) if I hope to extract stiffness matrix with reference to a point at 70m below the still water level, is it right?

K, f0 = moor.stiffness_matrix(epsilon=1e-5, point=(0,0,70))

[gbarter]

I do not know pyMAP or MAP well enough to answer this one. @mattEhall - do you?

[mattEhall]

Hi,
No, I'm not familiar enough with PyMAP to give confident advice. Though I'm pretty sure MAP uses the same convention as our other tools, with z positive up, so I'd assume that a point 70 m below the water level should be indicated as (0,0,-70).

You might find MoorPy helpful. It's a more current pure-Python alternative to MAP. You can read in MoorDyn-style input files and query it for various stiffness properties. https://github.com/NREL/MoorPy

Matt

[WTurbine]

Thank you for your comments, the coordinate of a point 70 m below the water level is indeed (0,0,-70).

Best regards,

[ebranlard]

Have you tried the dev branch? I should have included additional functions and updates so that matrices can be translated from oe point to another with error.

To extract the stiffness matrix at a given point the syntax is now:
https://github.com/WISDEM/pyMAP/blob/dev/examples/Ex1_StiffnessMatrixAndLoads.py#L50

Which uses a "point" as argument, to know where the loads have to be translated to, and it makes use of the values of the forces at the operating point via the function f_op that I added to the MAP library and the python interface:
https://github.com/WISDEM/pyMAP/blob/dev/src/pymap/pymap.py#L779

This dates back to quite some time now...

I personally use the following version of the python code (not sure how much difference it has with the dev branch):
https://github.com/ebranlard/welib/blob/dev/welib/moor/mappp.py
and I typically use it like this:
https://github.com/ebranlard/welib/blob/dev/welib/yams/windturbine.py#L958

[WTurbine]

Hi,

Thank you for your kindly reply. I have tried the dev branch and I can extract mooring stiffness matrix now. Also the matrix can be translated from one point to another (

pyMAP/examples/Ex3_StiffnessMatrixFromFST.py

Line 20 in b75e20a

K, f0 = moor.stiffness_matrix(epsilon=1e-5, point=(0,0,25))

). And the matrix matched the results provided by OpenFAST as shown below. And I really appreciate the information you shared.

Thank you again and have a nice day.

Mooring stiffness matrix from pymap
41181 0 0 0 -2815428 0
0 41181 0 2815430 0 0
0 0 11941 0 0 0
0 2815431 0 310785098 0 -49
-2815429 0 0 0 310784963 0
0 0 0 -81 0 11566656

Mooring stiffness matrix from document of OpenFAST
41180 0 0 0 -2821000 0
0 41180 0 2821000 0 0
0 0 11940 0 0 0
0 2821000 0 311100000 0 0
-2821000 0 0 0 311100000 0
0 0 0 0 0 11560000