Verification of a new tool chain that uses BeamDyn

Dear all,

I am currently testing and verifying a new tool chain that uses BeamDyn as FEMsolver.
I have already been verifying some analytical beam test cases that worked so far.
As this tool chain will be used to examine the behavior of rotating composite rotors later on, I would like to make sure that transformations and the complete tool chain work correctly.
That’s the reason why I am looking for some results, which are already verified, such like the static analysis of a simple composite beam and the [b]analysis of a rotating beam /b.

I would be pleased if there are some papers or test cases, that apply to my request.

Many thanks in advance for any help.
Best regards
John

Dear John,

You can find various examples were we tested the correctness of BeamDyn in the following publications:

nrel.gov/docs/fy14osti/60759.pdf
nrel.gov/docs/fy15osti/63165.pdf
nrel.gov/docs/fy16osti/65115.pdf
onlinelibrary.wiley.com/doi/ful … 02/we.2101

Best regards,

Dear Jason,

many thanks for your fast reply.

As I use BECAS for creating the mass and stiffness matrices, I would be glad if you could submit me the corresponding material (E,G,μ,ρ) and cross section properties for the isotropic and anisotropic beam you are using in your test cases.
With those informations I can create the same conditions like you’ve in your benchmarking cases.
This gives me the possibility to verify the whole tool chain, because I don’t want to verify BeamDyn as I know that BeamDyn has already been extensively investigated.

Moreover, I haven’t found any test cases for a rotating beam in the papers you recommended me.
Are there any results for a simple rotating beam (isotropic) with an applied force, that I can use for my verification?

Furthermore, I recently wanted to verify the eigenvalues and eigenshapes of a simple beam.
Therefore I used the 36x36 full stiffness and mass matrices that are also generated in the .sum-file of BeamDyn. The comparison between my analytical results of the beam oszillation and the FEM solution using the full stiffness and mass matrices shows no match.
The FEM solution shows in addition, as seen in the picture, a displacement at the clamping (z=0) when considering a certain eigenshape - this shouldn’t be!
I would be pleased if you could tell me how the full 36x36 matrices are generated and whether I can use them to solve the eigenvalue problem.

Many thanks in advance.
Best regards,
John

https://www.dropbox.com/s/fgrf9hjmrt0ul1s/Beam_Eigenshape.png?dl=0

Dear John,

I don’t have more detailed information on cross-sectional properties than what is provided in the papers. You may be able to get these by reaching out to the lead author(s) directly (who may not check this forum regularly).

One of the BeamDyn module tests in the OpenFAST regression testing suite (r-test) is for a rotating beam: github.com/OpenFAST/r-test/tree … MW_dynamic, but this is for the NREL 5-MW turbine blade rather than for an isotropic blade. You could, of course, modify this test case if you wished.

The full mass and stiffness matrices written to the BeamDyn summary file do not include the cantilevered root boundary condition. Thus, the matrices reflect a free-free boundary condition rather than a fixed-free condition. You can apply a fixed-free condition by eliminating the first six rows and columns from each matrix before running the eigenanalysis.

Best regards,

Dear Jason,

many thanks for your reply.
I will try to contact the authors of the corresponding papers and will also modify the full mass and stiffness matrices as suggested by you.

Best regards,
John

Dear Jason,

the modification of the full mass and stiffness matrices as suggested by you worked so far for a static case.
My question is, if I can use these assembled full mass and stiffness matrices also for a rotating case to solve the eigenvalue problem when inertial forces such as the centrifugal force or the Coriolis force occur.

Many thanks in advance.

Best regards,
John

Dear John,

No, the mass and stiffness matrices written to the BeamDyn summary file do not include the effects (such as centrifugal stiffening) from rotor rotation.

That said, we’ve recently collaborated with Envision Energy USA, Ltd. to introduce the linearization of BeamDyn within the full-system linearization of OpenFAST (including the effects of rotation rotation and coupling with the support structure). We are currently working on further verification and documentation of this capability. While not yet fully documented, this capability has already been merged into OpenFAST: github.com/OpenFAST/openfast. In the interim, please find a presentation attached that summarizes the theoretical basis and verification results.

OpenFASTBeamDynLinearization_EnvisionMeeting181030_Jonkman_Presentation.pdf (782 KB)
Best regards,

Dear Jason,

many thanks for your reply.
I would now like to generate a Campbell diagram for the rotor I am considering.
Which modules of the OpenFast framework do I need in order to achieve this?

Many thanks in advance.

Best regards,
John

Dear John,

The process for calculating natural frequencies at different rotor speeds using FAST/MBC3 and plotting the Campbell diagram has been discussed several times on this forum e.g. http://forums.nrel.gov/t/campbell-diagram-mbc3-output-relation/687/9.

Best regards,