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by Jason.Jonkman
Fri Jun 18, 2021 11:22 am
Forum: Structural Analysis
Topic: Stability analysis of operating wind turbines (NREL 5MW Onshore)
Replies: 1
Views: 35

Re: Stability analysis of operating wind turbines (NREL 5MW Onshore)

Dear Javier, Alvaro, and Aitor, Overall, it sounds like you understand the linearization process and are following the correct approach. The big difference between method B and methods A and C is that the generator DOF has been disabled in B. This will eliminate the rigid-body mode and have some inf...
by Jason.Jonkman
Fri Jun 18, 2021 9:48 am
Forum: Controls
Topic: Processing linearization output to obtain PID controller coefficients
Replies: 3
Views: 37

Re: Processing linearization output to obtain PID controller coefficients

Dear Jannik, I haven't reviewed all your files, but just a few comments: ⋅ When you don't have any states in the rotating frame, then MBC3 does not apply, but you can still azimuth-average the matrices. ⋅ As the forum post linked above discussed, you should eliminate the column a...
by Jason.Jonkman
Thu Jun 17, 2021 11:28 am
Forum: Controls
Topic: Processing linearization output to obtain PID controller coefficients
Replies: 3
Views: 37

Re: Processing linearization output to obtain PID controller coefficients

Dear Jannik, Just a couple comments: ⋅ MBC and azimuth-averaging should eliminate the influence of the generator-azimuth state, which should then be removed from the linear model before use. This is discussed e.g. in the following forum topic: https://wind.nrel.gov/forum/wind/viewtopic.php...
by Jason.Jonkman
Thu Jun 17, 2021 10:48 am
Forum: Computer-Aided Engineering Software Tools
Topic: Hydrodynamic coefficients HELP!
Replies: 32
Views: 1434

Re: Hydrodynamic coefficients HELP!

Dear Bartosz, Regarding (1), the center of rotation of the floating wind system is not directly output by OpenFAST, but can be calculated through knowledge of the platform motions (e.g., seeing how the support structure displacement varies along the support structure). But it is possible that center...
by Jason.Jonkman
Thu Jun 17, 2021 10:35 am
Forum: Computer-Aided Engineering Software Tools
Topic: Hydrodyn standalone
Replies: 3
Views: 37

Re: Hydrodyn standalone

Dear Nicolas,

NREL has not provided precompiled binaries for the standalone drivers of OpenFAST modules, but you can compile these yourselves using the available scripts, e.g. CMake for Mac or Linux and Visual Studio for Windows.

Best regards,
by Jason.Jonkman
Wed Jun 16, 2021 9:31 am
Forum: Computer-Aided Engineering Software Tools
Topic: Hydrodyn standalone
Replies: 3
Views: 37

Re: Hydrodyn standalone

Dear Deza, Which version of FAST or OpenFAST are you using? I'm not aware that we had a sample WAMIT time-series input file from FAST v8 or older versions of OpenFAST, but you could always review the standalone HydroDyn driver source code to figure out what exact format was required. However, it may...
by Jason.Jonkman
Wed Jun 16, 2021 9:20 am
Forum: Computer-Aided Engineering Software Tools
Topic: Error during linearization with VolturnUS-S
Replies: 8
Views: 58

Re: Error during linearization with VolturnUS-S

Dear Andre, Here are my answers to your questions: 1) Yes, you can plot the time series (e.g., of platform motions) to ensure that the solution is in equilibrium before linearizing. Enabling CalcSteady = True provides an automated way of ensuring the solution is in steady state before linearizing. 2...
by Jason.Jonkman
Tue Jun 15, 2021 11:39 am
Forum: Computer-Aided Engineering Software Tools
Topic: Error during linearization with VolturnUS-S
Replies: 8
Views: 58

Re: Error during linearization with VolturnUS-S

Dear Andre, The values you have obtained through the OpenFAST linearization are quite close to those reported. I'm not really familiar enough with the Volturn-US model or report to know how the reported values were obtained. Of course, you could check that the OpenFAST linearization results are conv...
by Jason.Jonkman
Tue Jun 15, 2021 11:25 am
Forum: Rotor Aerodynamics
Topic: two mass model
Replies: 1
Views: 18

Re: two mass model

Dear Cameron,

Are you asking what value ElastoDyn calculates for the rotor inertia? This is written to the ElastoDyn summary file, *.ED.sum, which is written when OpenFAST is run with SumPrint = True set in ElastoDyn.

Best regards,
by Jason.Jonkman
Tue Jun 15, 2021 11:22 am
Forum: NWTC Wind Data
Topic: Offshore Wind Data
Replies: 17
Views: 11547

Re: Offshore Wind Data

Dear Salem,

The previous website (the NWTC Information Portal) where that spreadsheet was stored has been taken down. You can now find that spreadsheet on my Google drive: https://drive.google.com/file/d/1zeiYQo ... sp=sharing.

Best regards,
by Jason.Jonkman
Mon Jun 14, 2021 4:51 pm
Forum: Computer-Aided Engineering Software Tools
Topic: Hydrodynamic coefficients HELP!
Replies: 32
Views: 1434

Re: Hydrodynamic coefficients HELP!

Dear Bartsoz, The off-diagonal terms come from the fact that the mooring line fairleads are not placed at (0,0,0). So, the force caused by translation will result in moment; likewise rotation will cause a force. The sign is based on the coordinate system with surge-pitch coupling the opposite sign (...
by Jason.Jonkman
Mon Jun 14, 2021 3:42 pm
Forum: Computer-Aided Engineering Software Tools
Topic: ServoDyn error
Replies: 1
Views: 37

Re: ServoDyn error

Dear Bruce, Not all precompiled binary executables of OpenFAST require the Intel redistributable libraries; the ones that do were built to require dynamic libraries from Intel rather than being compiled with Intel static libraries. I don't recall what OpenFAST v1.0.0 requires, but regardless, I woul...
by Jason.Jonkman
Mon Jun 14, 2021 3:30 pm
Forum: Computer-Aided Engineering Software Tools
Topic: Direct drive generator and edgewise bending of the blades
Replies: 4
Views: 70

Re: Direct drive generator and edgewise bending of the blades

Dear Bartosz, I agree with your interpretation of the drivetrain DOF in the ElastoDyn module of FAST / OpenFAST. And I agree that for direct-drive wind turbines, with a short, stiff shaft, that the drivetrain DOF can be disabled. I'm not sure which baseline controller you are referring to, but a low...
by Jason.Jonkman
Mon Jun 14, 2021 3:17 pm
Forum: Computer-Aided Engineering Software Tools
Topic: Two-blades wind turbine
Replies: 5
Views: 115

Re: Two-blades wind turbine

Dear Tianhui.Liu, I'm not sure I know the history all models in the OpenFAST r-test are set up the way the are, but they are more set up as examples that can be used to test the various functionality of OpenFAST. Regarding AWT_YFree_WTurb, this model is set up with GenDOF = False and RotSpeed = 53.3...
by Jason.Jonkman
Fri Jun 11, 2021 10:55 am
Forum: Computer-Aided Engineering Software Tools
Topic: FAST theory manual
Replies: 375
Views: 83503

Re: FAST theory manual

Sent.

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