## Emergency shutdown

Discuss the theory and modeling of rotor aerodynamics.

Moderator: Bonnie.Jonkman

Jason.Jonkman
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Location: Boulder, CO
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### Re: Emergency shutdown

Dear Moritz,

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

### Re: Emergency shutdown

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 (24.93 KiB) Viewed 1973 times
Tip_Torsion.png (26.1 KiB) Viewed 1973 times
Pitch.png (21.4 KiB) Viewed 1973 times

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

### Re: Emergency shutdown

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 (25.14 KiB) Viewed 1972 times
Pitch_5Hz.png (22.18 KiB) Viewed 1972 times
Tip_Torsion_5Hz.png (35.2 KiB) Viewed 1972 times

Jason.Jonkman
Posts: 5728
Joined: Thu Nov 03, 2005 4:38 pm
Location: Boulder, CO
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### Re: Emergency shutdown

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

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 (19.96 KiB) Viewed 1939 times
RotAeroFyh.png (33.06 KiB) Viewed 1939 times

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

### Re: Emergency shutdown

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 (17.48 KiB) Viewed 1933 times
aoa at 350s.png (20.15 KiB) Viewed 1933 times

Jason.Jonkman
Posts: 5728
Joined: Thu Nov 03, 2005 4:38 pm
Location: Boulder, CO
Contact:

### Re: Emergency shutdown

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