BeamDyn Input

Provide feedback, request enhancements, and get help with wind-turbine computer-aided engineering tools.

Moderators: Bonnie.Jonkman, Jason.Jonkman

Farhad.Abtahi
Posts: 9
Joined: Tue Nov 28, 2017 8:28 am
Organization: ITU
Location: Turkey

BeamDyn Input

Postby Farhad.Abtahi » Mon Dec 11, 2017 8:13 am

Dear all,

I've got outputs from Numad + Precomp and trying to create my own BeamDyn input file to use in FAST.
Majority of needed data are obtained from Numad's output but there are some missing pieces and confusion.

questions:
1_how can I obtain edge and flap shear stiffnesses?

Page 15* in BeamDyn manual decsribes what Damping Coefficient is but I can not fully understand it.
2_Should I put a standard value for Damping Coefficient or do I need to calculate my own Damping Coefficient by using the formula in page 15?

*Page 15 from BeamDyn User’s Guide:
https://wind.nrel.gov/nwtc/docs/BeamDyn ... df#page=18

Any guidance or information is greatly appreciated.

Sincerely,
Farhad

Relevant data and BymDyn manual are shwon the picture below.
Attachments
1 INDIVIDUAL BLADE INPUT FILE.png
1 INDIVIDUAL BLADE INPUT FILE.png (480.86 KiB) Viewed 2602 times

Jason.Jonkman
Posts: 4969
Joined: Thu Nov 03, 2005 4:38 pm
Location: Boulder, CO
Contact:

Re: BeamDyn Input

Postby Jason.Jonkman » Mon Dec 11, 2017 9:08 am

Dear Farhad,

PreComp does not model the shear terms, so, it cannot be used to calculate the edge and flapwise shear stiffness. NuMAD should be able to calculate the shear stiffness, but I'm not familiar enough with the software to know how to output it.

Basically, BeamDyn uses stiffness--proportional structural damping. A setting of 0.01 for all coefficients is reasonable in the absence of more information.

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

Paul.Feja
Posts: 16
Joined: Thu Aug 03, 2017 6:00 am
Organization: Fraunhofer IWES
Location: Germany

Re: BeamDyn Input

Postby Paul.Feja » Thu Jan 04, 2018 4:19 am

Dear Jason,

I have noticed that you recommend a setting of mu = 0.01 as reasonable here, whilst for the NREL5MW reference blades mu = 0.001 is preset. I lack a good feeling for the physical meaning as well as the values of these damping coefficients, as they differ from typical modal damping or Rayleigh damping values used in aeroelastic analyses. Is there any method to have a rough estimate of the damping values for BeamDyn, e.g. based on modal damping?

Thank you for your support.

Paul

Jason.Jonkman
Posts: 4969
Joined: Thu Nov 03, 2005 4:38 pm
Location: Boulder, CO
Contact:

Re: BeamDyn Input

Postby Jason.Jonkman » Thu Jan 04, 2018 6:52 am

Dear Paul,

You could select the stiffness-proportional damping in BeamDyn based on a damping ratio (zeta) and natural frequency (f, in Hz) of a given mode using the standard relationship mu = zeta/(pi*f), with the understanding that stiffness-proportional damping produce damping ratios that scale linearly with frequency. For example, a damping ratio of 2% and a frequency of 0.6 Hz results in mu of a approximately 0.01 s.

I don't recall why mu is set to 0.001 s for the example BeamDyn model of the NREL 5-MW reference wind turbine, but I agree that this is inconsistent with the specification for this turbine. Perhaps the structural damping was reduced to compensate for the numerical damping intrinsically included in BeamDyn's generalized-alpha time integrator (depending on the setting of rhoinf).

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

Paul.Feja
Posts: 16
Joined: Thu Aug 03, 2017 6:00 am
Organization: Fraunhofer IWES
Location: Germany

Re: BeamDyn Input

Postby Paul.Feja » Thu Jan 04, 2018 8:05 am

Jason.Jonkman wrote:Dear Paul,
You could select the stiffness-proportional damping in BeamDyn based on a damping ratio (zeta) and natural frequency (f, in Hz) of a given mode using the standard relationship mu = zeta/(pi*f), with the understanding that stiffness-proportional damping produce damping ratios that scale linearly with frequency. For example, a damping ratio of 2% and a frequency of 0.6 Hz results in mu of a approximately 0.01 s.

Dear Jason,

thanks for your quick help. I've had never worked with stiffness-proportional damping and was confused with mu being a non-dimensional damping ratio, as the BeamDyn_Blade input file header of the NREL5MW suggests that mu didn't have any unit.

Regards
Paul

Jason.Jonkman
Posts: 4969
Joined: Thu Nov 03, 2005 4:38 pm
Location: Boulder, CO
Contact:

Re: BeamDyn Input

Postby Jason.Jonkman » Thu Jan 04, 2018 8:53 am

Dear Paul,

Yes, the structural damping coefficient in BeamDyn (mu) has the units of 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

Pouria.Amouzadrad
Posts: 2
Joined: Mon May 20, 2019 8:36 am
Organization: ECN
Location: France

Re: BeamDyn Input

Postby Pouria.Amouzadrad » Tue May 21, 2019 3:56 am

Dear all,

Currently, I am struggling with stand-alone BeamDyn input files( Dvr_5MW_static.inp, Static_BeamDyn_input_5MW.inp, 5MW_Blade_IEC.inp). I wonder if you could help me to change the length of the blade in the input file and also I wanted to know the difference between nodes and number of key points on member(kp_total). because for instance I want to consider 6 nodes on the member and then applying force on each node.

Regards,
Pouria

Jason.Jonkman
Posts: 4969
Joined: Thu Nov 03, 2005 4:38 pm
Location: Boulder, CO
Contact:

Re: BeamDyn Input

Postby Jason.Jonkman » Wed May 22, 2019 1:19 am

Dear Pouria,

It looks like you've posted the same question in OpenFAST issues (https://github.com/OpenFAST/openfast/issues/140), which has now been answered by Jelmer Polman, with a reference to the following forum topics:

viewtopic.php?f=4&t=1525
viewtopic.php?f=4&t=2046&p=11114

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

Jan.Lange
Posts: 1
Joined: Thu Jun 25, 2020 5:50 am
Organization: Leibniz Universität Hannover
Location: Germany

Re: BeamDyn Input

Postby Jan.Lange » Mon Jun 29, 2020 5:12 am

Dear Jason,

I’d like to follow up on the calculation of the damping coefficient used in BeamDyn (mu).
I’ve got some measurement data of a rotor blade and would like to use the measured damping ratios in BeamDyn to improve my simulations.
Based on the measured natural frequencies and damping ratios I’m able to calculate the damping coefficient for a given mode as described above.
I’ve got data for the following eigenmodes:
- Rigid Body Heave, Roll, and Pitch
- 1., 2. and 3. bending flapwise
- 1., 2. and 3. bending edgewise
- 1. and 2. torsion.

My problem now is, that I’m not certain how to transfer those calculated mu into BeamDyn; i.e. the data of which mode to use for which mu (1,1 – 6,6).
Also the calculated mu are decreasing drastically with increasing mode order (no linearly scaling) and the mu of the rigid body modes are about 100-times greater than the other (0.01 vs. 0.0001).
This behavior also produces the following warning when running BeamDyn with the mu based on the measurement:
FAST_InitializeAll:BD_Init:BD_ValidateInputData:Damping values in blade file are not of similar
order of magnitude. BeamDyn may not converge!

Is there any additional documentation on this besides the ‘damping coefficient’ section in the BeamDyn User Guide?

Best regards,
Jan

Jason.Jonkman
Posts: 4969
Joined: Thu Nov 03, 2005 4:38 pm
Location: Boulder, CO
Contact:

Re: BeamDyn Input

Postby Jason.Jonkman » Mon Jun 29, 2020 6:53 am

Dear Jan,

I'm not aware of any other BeamDyn documentation than what is included on OpenFAST readthedocs: https://openfast.readthedocs.io/en/mast ... index.html.

I'm not sure what you mean by damping of rigid-body modes. Damping is not really defined for rigid body modes and BeamDyn itself does not support rigid-body modes.

BeamDyn only supports stiffness-proportional damping, so, you'll be able to match the damping of one mode (likely the first mode), but not all modes. With stiffness-portional damping, the damping will increase with increasing frequency. If I have known damping values for the flapwise, edgewise, and torsion modes, would normally tune mu55 to the correct damping of the first flapwise mode, mu44 to the correct damping of the first edgewise mode, and mu66 to the correct damping of the first torsion mode. The values of mu11, m22, and m33 are likely less critical, but you could set them to values similar to mu44, mu55, and mu66.

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


Return to “Computer-Aided Engineering Software Tools”

Who is online

Users browsing this forum: No registered users and 1 guest