## Emergency shutdown

Discuss the theory and modeling of rotor aerodynamics.

Moderator: Bonnie.Jonkman

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

### Emergency shutdown

Dear Jason,
I work witch OpenFast (Version: 2.1.0-183-g33a4f844-dirty)
I want to simulate the Emergency Shutdown DLC 5.1 (IEC standard). I’m using the model of the NREL 5 MW reference wind turbine. The wind turbine is seeing the conditions V_hub = 13,4 (NTM). The shutdown engages at 300s. To simulate this case I set the Parameters to:
ServoDyn
TPitManS = 300 s
PitManRat = 8 °/s
BlPitchF = 90 °
GenTiStp = True
TimGenof = 300 s

ElastoDyn
GenDOF = True

AeroDynV15
WakeMod = 2
DBEMT_Mod = 2
UAMod = 3
In Comparison to the other forum topics
viewtopic.php?f=2&t=2419&hilit=shut+down and
viewtopic.php?f=2&t=2351&hilit=shut+down
Till 320 s everything looks as expected. After that it seems the turbine is oscillation and the pitching moment gets surprisingly high. Do you have any suggestions to improve the control?

Best regards
Moritz Pick
Attachments
RotSpeed
RotSpeed.png (13.55 KiB) Viewed 2657 times
pitching Moment
Pitchmoment.png (19.36 KiB) Viewed 2657 times
Azimuth Angle
Azimuth.png (34.38 KiB) Viewed 2657 times

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

### Re: Emergency shutdown

Dear Jason,

I forgot to mention, that I'm using BeamDyn instead of ElastoDyn.

Best regards
Moritz

Jason.Jonkman
Posts: 5738
Joined: Thu Nov 03, 2005 4:38 pm
Location: Boulder, CO
Contact:

### Re: Emergency shutdown

Dear Moritz,

Well, I'm not sure. I would guess the strong oscillation in rotor speed and blade-root moment are related. Do you get the same behavior with simplified aerodynamics, i.e., WakeMod = 1, AFAeroMod = 1?

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 simulated this load case with simplified aerodynamics. The behaviour of the wind turbine looks much better, there ist no oscillation. I think there is no problem with the controll setup. So now there is the question, if a complex aerodynamics and a complex structual beam results in oscillation?

Best regards
Moritz
Attachments
Azimuth2.png (23.04 KiB) Viewed 2615 times
Pitching Moment.png (16.96 KiB) Viewed 2615 times
RotSpeed2.png (14.48 KiB) Viewed 2615 times

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

### Re: Emergency shutdown

Dear Jason,

with simplified aerodynamics there is a different behaviour in the Pitch Controll. If you compare both simulations there is quite a different in the pitch angle. Does this results because of a different angle of attack?

Best regards
Moritz
Attachments
Pitch angle.png (16.52 KiB) Viewed 2614 times

Jason.Jonkman
Posts: 5738
Joined: Thu Nov 03, 2005 4:38 pm
Location: Boulder, CO
Contact:

### Re: Emergency shutdown

Dear Moritz,

I would first try to isolate which model is causing the strong oscillatory behavior. I would guess it is related to the unsteady airfoil aerodynamics model associated with the pitching moment, but that is just a guess. Do you get reasonable behavior with WakeMod = 2 and AFAeroMod = 1 and unreasonable behavior with WakeMod = 1 and AFAeroMod = 2?

I'm a bit surprised with your plot of pitch angle. I would normally expect dynamic wake and unsteady aerodynamics to effect the variations in response about the mean, not the mean itself. Are you getting reasonable structural response (blade and tower deflections, including blade twist) between 200-280 seconds?

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 isolated both models, it seems that AFAeroMod is causing the oscillatory behavior. The structual response seems reasonable.

Best regards
Moritz
Attachments
Pitch angle2.png (19.32 KiB) Viewed 2563 times
RotSpeed3.png (18.9 KiB) Viewed 2563 times

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

### Re: Emergency shutdown

Here is the deflection of the blade
Attachments
Deflection_z.png (24.95 KiB) Viewed 2562 times
Deflection_y.png (32.77 KiB) Viewed 2562 times
Deflection_x.png (26.17 KiB) Viewed 2562 times

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

### Re: Emergency shutdown

Here is the tower deflection. The Last ones seems a bit off.

Best Regards
Moritz
Attachments
TTDspFa.png (32.4 KiB) Viewed 2556 times
TTDspAx.png (32.74 KiB) Viewed 2556 times
TTDspSS.png (33.13 KiB) Viewed 2556 times

Jason.Jonkman
Posts: 5738
Joined: Thu Nov 03, 2005 4:38 pm
Location: Boulder, CO
Contact:

### Re: Emergency shutdown

Dear Moritz,

From these results, it certainly looks like the unsteady airfoil aerodynamics model (AFAeroMod = 2) is causing the strong oscillations after the shut down. You haven't stated how you've set the unsteady airfoil aerodynamic coefficients in the airfoil data files, but you may need to play with these values to get proper behavior. Reducing filtCutOff (say from "DEFAULT", which is 20 Hz, to 5 Hz) may be a good place to start.

It looks like the switch from BEMT (WakeMod = 1) to DBEMT (WakeMod = 2) has a large effect on the mean rotor speed and blade-pitch angle between 200-280 s. This still surprises me as I would expect this change to effect oscillations about the mean rather than the mean itself. What happens from 0-200 s? What does the blade-torsion look like?

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 didn't changed the unsteady airfoil coefficients in the airfoil data files.

For example these are the data for DU30 A17:

-2.2 alpha0
9 alpha1
-9 alpha2
1 eta_e
7.3326 C_nalpha
3 T_f0
6 T_V0
1.7 T_p
11 T_VL
0.14 b1
0.53 b2
5 b5
0.3 A1
0.7 A2
1 A5
0 S1
0 S2
0 S3
0 S4
1.449 Cn1
-0.6138 Cn2
0.19 St_sh
0.008 Cd0
-0.09 Cm0
0 k0
0 k1
0 k2
0 k3
0 k1_hat
0.2 x_cp_bar
"DEFAULT" UACutout
"DEFAULT" filtCutOff

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

### Re: Emergency shutdown

my next step will be to reduce the frequency to 5 Hz and to look into time between 0 and 200 s.

Best regards
Moritz

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

### Re: Emergency shutdown

Dear Jason,

in the the pictures are shown the the root Momentaround the x,y,z axis vom 0 to 200s with the same unsteady aerodynamic coeffizient
Attachments
RootMz.png (24.79 KiB) Viewed 2527 times
RootMy.png (36.58 KiB) Viewed 2527 times
RootMx.png (32.64 KiB) Viewed 2527 times

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

### Re: Emergency shutdown

here are the deflection in x,y,z direction at filtCutOff = 5
Attachments
Deflection z.png (44.69 KiB) Viewed 2526 times
Deflection y.png (49.84 KiB) Viewed 2526 times
Deflection x.png (42.65 KiB) Viewed 2526 times

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

### Re: Emergency shutdown

and here is the blade root torsion at filtCutOff = 5

Best regards Moritz
Attachments
RootMz2.png (32.04 KiB) Viewed 2524 times