Hi everyone,
I’m running an OpenFAST simulation (using BeamDyn and ElastoDyn) with an initial rotor speed, but I’m observing extreme blade deformations. It looks like the blades start with zero initial speed and deform significantly due to inertia.
In this picture the initial rotor speed was set to 2rpm and it’s showing the state after 10 s.
I’m wondering if my blade might not be stiff enough, but my stiffness and mass matrices are quite similar to those of the NREL 5MW Baseline. Has anyone encountered a similar issue before?
Best regards,
Linus
Dear @Linus.Wermert,
When an OpenFAST model with BeamDyn enabled is initialized with a nonzero RotSpeed
, the blades are initialized without flapwise or edgewise deflection, but are initialized with rotation, so, the initial RotSpeed
should not “kick” the system. If you are not expecting such large deflection, I would guess something is not set up properly in your OpenFAST model (likely in the BeamDyn input files), but I’m not sure what the issue would be without more information.
Best regards,
Dear @Jason.Jonkman
Thank you for your response. You were right—my BeamDyn input file was incorrect. The deviation moments in my mass matrix were wrong because I had used the wrong sign when applying Steiner’s theorem. Additionally, I changed the reference axis from the elastic axis to the aerodynamic center. Now, everything is working as expected.
Best regards,
Linus
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