BeamDyn Input

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Farhad.Abtahi
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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 1660 times

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


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