Emergency shutdown

Discuss the theory and modeling of rotor aerodynamics.

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Jason.Jonkman
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Re: Emergency shutdown

Postby Jason.Jonkman » Mon Jan 20, 2020 4:58 pm

Dear Moritz,

Actually, I was asking for the blade-tip twist (torsion).

And what do the rotor speed and blade-pitch angles look like from 0-200 s?

Does setting filtCutOff = 5 Hz give reasonable results during the shut down?

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

Moritz.Pick
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Organization: HAW Hamburg
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Re: Emergency shutdown

Postby Moritz.Pick » Tue Jan 21, 2020 8:45 am

Dear Jason,

in the picture is shown the rotor speed ,the pitch angle and the tip torsion form 0 to 200 second with the default setting 20 Hz
Attachments
Rotspeed.png
Rotspeed.png (24.93 KiB) Viewed 1977 times
Tip_Torsion.png
Tip_Torsion.png (26.1 KiB) Viewed 1977 times
Pitch.png
Pitch.png (21.4 KiB) Viewed 1977 times

Moritz.Pick
Posts: 30
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Organization: HAW Hamburg
Location: Germany

Re: Emergency shutdown

Postby Moritz.Pick » Tue Jan 21, 2020 8:48 am

Blade torsion, rotor speed and pitch angle at 0 to 400 seconds with filtCutOff = 5.
There ist no oscillation left at the results.

Best regards
Moritz
Attachments
Rotspeed_5Hz.png
Rotspeed_5Hz.png (25.14 KiB) Viewed 1976 times
Pitch_5Hz.png
Pitch_5Hz.png (22.18 KiB) Viewed 1976 times
Tip_Torsion_5Hz.png
Tip_Torsion_5Hz.png (35.2 KiB) Viewed 1976 times

Jason.Jonkman
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Joined: Thu Nov 03, 2005 4:38 pm
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Re: Emergency shutdown

Postby Jason.Jonkman » Tue Jan 21, 2020 9:01 am

Dear Moritz,

I'm not sure what you mean with B1N9MT (N). The tip twist would be something like B1TipRDzr (-).

The rotor speed and pitch angle look consistent (they are in Region 3 with WakeMod=1 and they are below Region 3 with WakeMod=2), but I don't really understand why this is the case. Assuming these simulations using exactly the same wind, for some reason your results are showing WakeMod = 2 results in less blade loading than WakeMod = 1. To understand further, I would probably simplify the model (zero degrees of freedom and fixed control) and look at the aerodynamic loads (RtAeroFxh and RtAeroMzh) to see how the loads differ for this case.

I can't tell from your plots, but do you get the response you expect with filtCutOff = 5 Hz?

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

Moritz.Pick
Posts: 30
Joined: Mon Dec 02, 2019 1:01 am
Organization: HAW Hamburg
Location: Germany

Re: Emergency shutdown

Postby Moritz.Pick » Wed Jan 22, 2020 8:30 am

Dear Jason,

I simplified the model. The wind speed is steady at 13.4 m/s. There is no degree of freedom an no pitch controll. The main difference of the aerodynamic loads is between WakeMod 1 and WakeMod 2. After pitching to feather, they are nearly the same.

Best regards
Moritz Pick
Attachments
RotAeroFxh.png
RotAeroFxh.png (19.96 KiB) Viewed 1943 times
RotAeroFyh.png
RotAeroFyh.png (33.06 KiB) Viewed 1943 times

Moritz.Pick
Posts: 30
Joined: Mon Dec 02, 2019 1:01 am
Organization: HAW Hamburg
Location: Germany

Re: Emergency shutdown

Postby Moritz.Pick » Wed Jan 22, 2020 8:46 am

The main difference should be the Aoa, therefore I plotted the angle at last four nodes at 200s and at 350 s.
Attachments
Aoa at 200s.png
Aoa at 200s.png (17.48 KiB) Viewed 1937 times
aoa at 350s.png
aoa at 350s.png (20.15 KiB) Viewed 1937 times

Jason.Jonkman
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Re: Emergency shutdown

Postby Jason.Jonkman » Wed Jan 22, 2020 8:17 pm

Dear Moritz,

Clearly enabling DBEMT (WakeMod=2) is resulting in a bad solution.

What DBEMT settings are you using in AeroDyn?

Also, I noticed that you are using (some branch?) of OpenFAST v2.1. When DBEMT was first introduced into OpenFAST, there was an issue in the OpenFAST glue code that would require that a correction step be added (NumCrctn>0) in some cases when DBEMT was enabled. This was fixed in pull request #164: https://github.com/OpenFAST/openfast/pull/164, which was merged into OpenFAST v2.2. So, you may need to add this correction step when enabling DBEMT in v2.1, but you shouldn't need to add this correction step if you upgrade to v2.2.

I hope that helps.

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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