OpenFAST SubDyn Module Linearization

Dear Jason,

With the inclusion of Subdyn module (and possibly MoordDyn) linearization capabilities, will the matlab-toolbox MBC transform require some additional modifications as done for the HydroDyn module in the paper “Verification of Floating Offshore Wind Linearization Functionality in OpenFAST”? That is, can I follow the steps highlighted in the paper to modify the code to be able to generate the correct system matrix and compute the system frequencies?

Thanks

Atinuke

Dear Atinuke,

With the recent merge of this pull request into the dev branch of OpenFAST, the dev branch of OpenFAST now has the ability to linearize models with SubDyn enabled. The full-system linearization capability of OpenFAST with MoorDyn enabled is not available yet, but is something we are working on now.

The existing MBC3 scripts in the MATLAB Toolbox (github.com/OpenFAST/matlab-toolbox) can be used without modification to identify the full-system mode shapes, natural frequencies, and damping based on OpenFAST linearization output, including models with SubDyn enabled. We have realized, though, that it may be useful to scale the Craig-Bampton modes of SubDyn differently to aid in interpretation of the full-system mode shapes for models with SubDyn enabled, which is not something we’ve worked on yet.

Best regards,

Dear Jason,

Thanks for your response. I have another question about the MoorDyn module.

When the MoorDyn module is set to 0 during the linearization process, does that mean that the tendon lines are rigid or that they are not considered present? This is because when I run a simulation with the MoorDyn set to 0, there is a platform surge of about 25m during the simulation, which is higher than I would expect if the tendon lines are rigid.

Thanks

Atinuke

Dear Atinuke,

If CompMooring = 0 in OpenFAST, then there are no moorings modeled at all and–as you noticed–I would expect the floating wind turbine to drift away, unless the platform DOFs in ElastoDyn are disabled.

Currently, full-system linearization of OpenFAST with moorings is possible with CompMooring = 1 (MAP++); we are adding the linearization with CompMooring = 3 (MoorDyn) now.

Best regards,

Hello Everybody,
I have encountered an error (please see the attachment) from MoorDyn module while running 15MW UmaineSemiSub in openfast. The error refer to the line 1 of the MoorDyn data input file.
When I switch to 1 (Map++), FAST encountered an error during module initialization.

Please do you have any idea that can help me fixing the problem ?

Kind regards,

Dear Raphael,

It appears that your MoorDyn input file is not formatted properly in the line properties table after NLines is entered.

I see that you are using OpenFAST v2.5. Did you change upgrade the IEA Wind 15-MW OpenFAST model that you obtained from here that is formatted for OpenFAST v2.4 to v2.5? If not, you’ll need to add the CtrlChan column to the line properties table in MoorDyn per this PR: github.com/OpenFAST/openfast/pull/565.

What error are you getting when you switch to MAP++?

Best regards,

Thank you Jason for the answer. I corrected the format and now it ok.
Here is the error when I switch to MAP++.
Kind regards,

OpenFAST

Copyright (C) 2021 National Renewable Energy Laboratory
Copyright (C) 2021 Envision Energy USA LTD

This program is licensed under Apache License Version 2.0 and comes with ABSOLUTELY NO WARRANTY.
See the “LICENSE” file distributed with this software for details.


OpenFAST-v2.5.0-dirty
Compile Info:

  • Compiler: Intel(R) Fortran Compiler 2021
  • Architecture: 64 bit
  • Precision: single
  • Date: Mar 24 2021
  • Time: 18:16:58
    Execution Info:
  • Date: 04/29/2021
  • Time: 16:26:51+0200

OpenFAST input file heading:
IEA 15 MW offshore reference model on UMaine VolturnUS-S semi-submersible floating platform

Running ElastoDyn.
Nodal outputs section of ElastoDyn input file not found or improperly formatted.
Running AeroDyn.
Nodal output section of AeroDyn input file not found or improperly formatted.
Warning: Turning off Unsteady Aerodynamics because C_nalpha is 0. (node 1, blade 1)
Warning: Turning off Unsteady Aerodynamics because C_nalpha is 0. (node 2, blade 1)
Warning: Turning off Unsteady Aerodynamics because C_nalpha is 0. (node 1, blade 2)
Warning: Turning off Unsteady Aerodynamics because C_nalpha is 0. (node 2, blade 2)
Warning: Turning off Unsteady Aerodynamics because C_nalpha is 0. (node 1, blade 3)
Warning: Turning off Unsteady Aerodynamics because C_nalpha is 0. (node 2, blade 3)
Running InflowWind.
Running HydroDyn.
Setting WaveTMax to 0.0 since WaveMod = 0
Calculating second order difference frequency wave kinematics.
Reading in WAMIT output with root name “.\HydroData/IEA-15-240-RWT-UMaineSemi”.
Computing radiation impulse response functions and wave diffraction forces.
Calculating second order difference-frequency force using the full quadratic transfer function.

FAST_InitializeAll:MAP_Init:MAP_WARNING[1] : Extra characters are present in the cable library
portion of the MAP input file. word: <(-)>
MAP_WARNING[1] : Extra characters are present in the cable library portion of the MAP input file.
word: <1>
MAP_WARNING[1] : Extra characters are present in the cable library portion of the MAP input file.
word: <2>
MAP_WARNING[1] : Extra characters are present in the cable library portion of the MAP input file.
word: <3>
MAP_WARNING[1] : Extra characters are present in the cable library portion of the MAP input file.
word: <------------
MAP_WARNING[1] : Extra characters are present in the cable library portion of the MAP input file.
word: <0.001>
MAP_WARNING[1] : Extra characters are present in the cable library portion of the MAP input file.
word: <3.0e6>
MAP_WARNING[1] : Extra characters are present in the cable library portion of the MAP input file.
word: <3.0e5>
MAP_WARNING[1] : Extra characters are present in the cable library portion of the MAP input file.
word: <1.0

FAST encountered an error during module initialization.
Simulation error level: FATAL ERROR

Aborting OpenFAST.

Intialization: MAP_WARNING[1] : Extra characters are present in the cable library portion of the MAP input file. word: <(-)>
MAP_WARNING[1] : Extra characters are present in the cable library portion of the MAP input file. word: <1>
MAP_WARNING[1] : Extra characters are present in the cable library portion of the MAP input file. word: <2>
MAP_WARNING[1] : Extra characters are present in the cable library portion of the MAP input file. word: <3>
MAP_WARNING[1] : Extra characters are present in the cable library portion of the MAP input file. word: <------------
MAP_WARNING[1] : Extra characters are present in the cable library portion of the MAP input file. word: <0.001>
MAP_WARNING[1] : Extra characters are present in the cable library portion of the MAP input file. word: <3.0e6>
MAP_WARNING[1] : Extra characters are present in the cable library portion of the MAP input file. word: <3.0e5>
MAP_WARNING[1] : Extra characters are present in the cable library portion of the MAP input file. word: <1.0>
MAP_WARNING[1] : Extra ch

Dear Raphael,

Again, this looks like an issue with your input file format, this time for your MAP++ input file. Can you confirm your MAP++ input file is formatted properly?

Best regards,

Yes I modified the map input according to the 5MW’s example provided in documentation. But I’m not sure that it’s ok. The error seems come from another file.

---------------------- LINE DICTIONARY ---------------------------------------
LineType Diam MassDenInAir EA CB CIntDamp Ca Cdn Cdt
(-) (m) (kg/m) (N) (-) (Pa-s) (-) (-) (-)
Material 0.3330 685.00 3.27E+9 1.0 0 0 0 0
---------------------- NODE PROPERTIES ---------------------------------------
Node Type X Y Z M B FX FY FZ
(-) (-) (m) (m) (m) (kg) (mˆ3) (N) (N) (N)
1 fix -837.8 0.00000 depth 0 0 # # #
2 Vessel -58.00 0.00000 -14.0 0 0 # # #
---------------------- LINE PROPERTIES ---------------------------------------
Line LineType UnstrLen NodeAnch NodeFair Flags
(-) (-) (m) (-) (-) (-)
1 Material 850.00 1 2
---------------------- SOLVER OPTIONS-----------------------------------------
Option
(-)
repeat 120 240

Dear Raphael,

I don’t really see any problem with the format of this MAP++ input file. I also don’t see any of the values listed in the error message included in this MAP++ input file. Perhaps you’ve identified the incorrect path or filename in the specification of MoorFile (line 31) of the OpenFAST primary (*.fst) input file?

Best regards,