OpenFast Regression tests

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Jason.Jonkman
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Re: OpenFast Regression tests

Postby Jason.Jonkman » Sat May 30, 2020 8:09 am

Dear Francesco,

If the plots look reasonable to you, I'm sure the solution is fine and you are can proceed running OpenFAST for your analysis.

The OpenFAST r-test is highly sensitive and will indicate failures due to differences in compiler, platform, precision, source code changes, etc., even though the results are clearly within engineering accuracy. This is something that needs to be fixed with the testing framework in the future.

Best regards,
Jason Jonkman, Ph.D.
Senior Engineer | National Wind Technology Center (NWTC)

National Renewable Energy Laboratory (NREL)
15013 Denver West Parkway | Golden, CO 80401
+1 (303) 384 – 7026 | Fax: +1 (303) 384 – 6901
nwtc.nrel.gov

Matteo.Rovelli
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Re: OpenFast Regression tests

Postby Matteo.Rovelli » Fri Apr 02, 2021 5:07 am

Dear all,

I have compiled OpenFAST with Windows Visual Studio 2019 and I tried running the regression tests.
23 out of 33 tests result PASSED but the other ones have quite high residuals at some point (I attach the results of the 5MW_Land_BD_DLL_WTurb)
I was wondering if I can proceed with my work or if there is somethign wrong.

Thank you very much in advance,
Matteo Rovelli


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Jason.Jonkman
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Re: OpenFast Regression tests

Postby Jason.Jonkman » Fri Apr 02, 2021 6:38 am

Dear Matteo,

How do the plots look for the cases that are failing?

Best regards,
Jason Jonkman, Ph.D.
Senior Engineer | National Wind Technology Center (NWTC)

National Renewable Energy Laboratory (NREL)
15013 Denver West Parkway | Golden, CO 80401
+1 (303) 384 – 7026 | Fax: +1 (303) 384 – 6901
nwtc.nrel.gov

Matteo.Rovelli
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Re: OpenFast Regression tests

Postby Matteo.Rovelli » Fri Apr 02, 2021 7:48 am

Dear Mr. Jonkman,

here is the report of the 5MW_Land_BD_DLL_WTurb case.
The pdf is splitted in two parts to respect dimensions constraint.

Best regards,
Matteo Rovelli
Attachments
part2.pdf
(2.69 MiB) Downloaded 17 times
Part1.pdf
(2.47 MiB) Downloaded 18 times

Rafael.Mudafort
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Re: OpenFast Regression tests

Postby Rafael.Mudafort » Wed Apr 07, 2021 10:47 am

Hi Matteo,

The differences shown in your plots look reasonable given the possibility of significant differences between your system and the one used to generate the baseline results. In my opinion, you are ok to proceed using the executable you've obtained.

Rafael

Matteo.Rovelli
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Re: OpenFast Regression tests

Postby Matteo.Rovelli » Sat Apr 10, 2021 10:11 am

Hi Rafael,

Thank you very much for your opinion!
I have tried replicating the data of the 5MW reference turbine and everything seems fine (except differences due to different version of Aerodyn).

Regards,
Matteo Rovelli

Sebastian.Hippel
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Re: OpenFast Regression tests

Postby Sebastian.Hippel » Mon May 03, 2021 9:00 am

Hello everyone,
I run the 5MW_Land_BD_DLL_WTurb.fst test with OpenFAST v2.5.0. I could not understand why the pitch angle signal oscillates even when the wind speed is constant at the rated wind speed of 12 m/s. can anyone explain this?

Best regards
Sebastian
Attachments
5MW_Land_BD_DLL_WTurb.jpg
5MW_Land_BD_DLL_WTurb.jpg (166.58 KiB) Viewed 18 times

Jason.Jonkman
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Re: OpenFast Regression tests

Postby Jason.Jonkman » Mon May 03, 2021 9:16 am

Dear Sebastian,

It looks like this model has not yet reached equilibrium and you are seeing the start-up transient. The oscillations in blade pitch are commensurate with the oscillations in rotor speed. The system is not in equilibrium because the blades and tower are initialized in the undeflected state whereas in equilibrium the blades and tower will be deflected as a result of the aerodynamic forces applied to the rotor. As with any aeroelastic simulation, it is best to neglect the start-up transient when post-processing the output.

Best regards,
Jason Jonkman, Ph.D.
Senior Engineer | National Wind Technology Center (NWTC)

National Renewable Energy Laboratory (NREL)
15013 Denver West Parkway | Golden, CO 80401
+1 (303) 384 – 7026 | Fax: +1 (303) 384 – 6901
nwtc.nrel.gov

Sebastian.Hippel
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Re: OpenFast Regression tests

Postby Sebastian.Hippel » Wed May 05, 2021 3:02 am

Dear Jason,
Thank you for your quick reply.

In the figure below the wind speed rises from 0 m/s to 12 m/s in the first 100 s. After that the wind speed keeps constant over the next 100s till the simulation time of 200 s. Finally, the wind speed jumps to 14 m/s and keeps constant till the end of the simulation. As you see the oscillations in the rotor speed and the pitch angle cannot be damped at wind speed of 12 m/s (unlike the jump to wind speed of 14 m/s). These oscillations have a period of circa 13 s, which do not match any of the natural frequency at 12 rpm in the Campbell diagram of the 5-MW WT. Therefore, I would expect that these oscillations are due to an excitation from the control system.

do you agree with that? Can you tell me which signal could I plot to figure out the reason of such oscillations?

Best regards
Sebastian
Attachments
5MW_Land_BD_DLL_WTurb_equilibrium.jpg
5MW_Land_BD_DLL_WTurb_equilibrium.jpg (172.25 KiB) Viewed 11 times

Jason.Jonkman
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Re: OpenFast Regression tests

Postby Jason.Jonkman » Wed May 05, 2021 6:42 am

Dear Sebastian,

I agree that the oscillations appear to be coming from the controller. I would guess the 13-s period (0.077 Hz frequency) is coming from the PI-based blade-pitch controller. Did you change this OpenFAST model (of the NREL 5-MW baseline wind turbine with blades modeled in BeamDyn) in any way, other than the wind speed and initial conditions? It appears that the gains in the gain-scheduled pitch controller may need to be adjusted (increased) at low pitch angles. Perhaps this is because the controller was originally designed for this model with the blades modeled in ElastoDyn, which does not consider blade torsion. I'm curious how much blade twist you are seeing from BeamDyn during this simulation (TipRDzr)?

Best regards,
Jason Jonkman, Ph.D.
Senior Engineer | National Wind Technology Center (NWTC)

National Renewable Energy Laboratory (NREL)
15013 Denver West Parkway | Golden, CO 80401
+1 (303) 384 – 7026 | Fax: +1 (303) 384 – 6901
nwtc.nrel.gov


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