The prebent blade and aerodyn15

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Abhinay.Goga
Posts: 40
Joined: Tue Oct 25, 2016 8:12 am
Organization: SETEC elektronische Antriebsregelung GmbH
Location: Germany

Re: The prebent blade and aerodyn15

Postby Abhinay.Goga » Wed Sep 23, 2020 6:52 am

Dear Jason,

Maybe I wasn't explaining my self very well.
Standalone beamdyn + order_elem 4 = 0.04s time step (the smallest verified)
Standalone beamdyn + order_elem 33 = 0.002s time step
Coupled to OpenFAST + order_elem 4 = 0.0001s time step
My aim is to reduce the time step so that the total simulation time can be reduced considerably.

Thanks and kind regards

Jason.Jonkman
Posts: 5733
Joined: Thu Nov 03, 2005 4:38 pm
Location: Boulder, CO
Contact:

Re: The prebent blade and aerodyn15

Postby Jason.Jonkman » Wed Sep 23, 2020 8:21 am

Dear Abhinay,

OK, thanks for clarifying your question; I know understand. But I think I also answered them in prior posts:
  • The time steps are dictated by the natural frequencies present, and so, depend on the mass, stiffness, and numbers of degrees of freedom (DOFs);
  • Increasing order_elem will introduce additional DOFs and higher-frequency modes that require smaller time step; and
  • OpenFAST requires smaller time steps than BeamDyn standalone due to the existence of high-frequencies transferred through the glue code.
So, to reduce the time step requires reducing the highest frequencies either by changing the mass/stiffness or reducing the number of DOFs (order_elem). From prior posts, it is my understanding that you are questioning some of the mass/stiffness values you are using (perhaps leading to higher than expected frequencies, requiring smaller than expected time steps).

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

Abhinay.Goga
Posts: 40
Joined: Tue Oct 25, 2016 8:12 am
Organization: SETEC elektronische Antriebsregelung GmbH
Location: Germany

Re: The prebent blade and aerodyn15

Postby Abhinay.Goga » Thu Sep 24, 2020 12:17 am

Dear Jason,

Thanks for the detailed explanations. I verified the NREL_5MW example files with standalone beamdyn driver and the solution converges for 0.25s (smallest). As explained in the previous post, my model with very less DOFs converges at 0.04s. I am assuming it is the result of high frequencies induced by the mass/stiffness matrices. In another thread you mentioned NREL didn't compute the matrices using any additional software like BECAS, NuMAD or VABS. But calculated from the NREL 5MW blade profile itself. With your expertise, could you recommend any software among the mentioned or other procedures to compute the matrices? (Opensource if possible)

Thanks and kind regards

Jason.Jonkman
Posts: 5733
Joined: Thu Nov 03, 2005 4:38 pm
Location: Boulder, CO
Contact:

Re: The prebent blade and aerodyn15

Postby Jason.Jonkman » Thu Sep 24, 2020 7:28 am

Dear Abhinay,

VABS, BECAS, and NuMAD are all great options for sectional analysis. Another is ANisotropic Beam Analysis (ANBA). NREL recently combined VABS and ANBA together through OpenMDAO to support optimization of wind turbine blades in the Structural OptimizatioN and AeroelasTic Analysis (SONATA) framework--see: https://www.nrel.gov/docs/fy20osti/76877.pdf.

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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