Comparison between Bladed and OpenFAST - blade loads

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Kemal.Kartal
Posts: 35
Joined: Mon Jan 11, 2016 5:01 am
Organization: self
Location: Germany

Comparison between Bladed and OpenFAST - blade loads

Postby Kemal.Kartal » Tue Feb 11, 2020 3:41 pm

Hello,

I am comparing Bladed and OpenFAST (ElastoDyn). Can some tell me the issue for the higher range (oscillation) of the Blade loads after reaching rated power?

I think, My is the result of the higher Oscillating Fx, but why is Fx oscillating higher?

I generated a power curve, here are the results (orange is always OpenFAST and blue is Bladed):

I hope, someone can help me.

Best regards
Kemal
Attachments
01_Pwr_Curve.png
01_Pwr_Curve.png (24.12 KiB) Viewed 169 times
02_Pitch.png
02_Pitch.png (22.97 KiB) Viewed 169 times
Last edited by Kemal.Kartal on Tue Feb 11, 2020 3:44 pm, edited 2 times in total.

Kemal.Kartal
Posts: 35
Joined: Mon Jan 11, 2016 5:01 am
Organization: self
Location: Germany

Re: Comparison between Bladed and OpenFAST - blade loads

Postby Kemal.Kartal » Tue Feb 11, 2020 3:42 pm

Here are The Forces.
Attachments
Fx.png
Fx.png (76.2 KiB) Viewed 168 times
Fy.png
Fy.png (108.84 KiB) Viewed 168 times
Fz.png
Fz.png (87 KiB) Viewed 168 times

Kemal.Kartal
Posts: 35
Joined: Mon Jan 11, 2016 5:01 am
Organization: self
Location: Germany

Re: Comparison between Bladed and OpenFAST - blade loads

Postby Kemal.Kartal » Tue Feb 11, 2020 3:42 pm

Here are the moments.
Attachments
Mx.png
Mx.png (101.25 KiB) Viewed 167 times
My.png
My.png (61.79 KiB) Viewed 167 times
Mz.png
Mz.png (101.24 KiB) Viewed 167 times

Jason.Jonkman
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Location: Boulder, CO
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Re: Comparison between Bladed and OpenFAST - blade loads

Postby Jason.Jonkman » Thu Feb 13, 2020 9:04 am

Dear Kemal,

Well, the oscillations in the blade-root loads are likely driven by gravity, shear, rotor tilt, etc. Without knowing more about the model set ups, I don't think I can comment on why the FAST results are different than the results from Bladed. I would guess there are some differences in the model set up or output coordinate system.

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

Kemal.Kartal
Posts: 35
Joined: Mon Jan 11, 2016 5:01 am
Organization: self
Location: Germany

Re: Comparison between Bladed and OpenFAST - blade loads

Postby Kemal.Kartal » Fri Feb 14, 2020 8:02 am

Hi,

In both simulations the acceleration of gravity is 9.81 m/s^2. The blade mass and the rotor mass moment of inertia in the Elastodyn summary are equal. The tilt is also equal. The shear is in both simulations 0.

Do you have other parameters to check?

The four other channels are mostly the same. Fx and My are very near to each other till reaching rated power. But the pitch angle is not so different and thats why im weird.

I do not know what to check.

Best regards
Kemal

Jason.Jonkman
Posts: 4539
Joined: Thu Nov 03, 2005 4:38 pm
Location: Boulder, CO
Contact:

Re: Comparison between Bladed and OpenFAST - blade loads

Postby Jason.Jonkman » Fri Feb 14, 2020 8:46 am

Dear Kemal,

Do you much closer results if you disable all structural degrees of freedom (i.e., keeping the turbine rigid) in both models?

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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