Extreme blade deflection when starting with an initial rotor speed

Wind & Water Computer-Aided Engineering Software Tools
1

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.

Extreme_Rotor_deflection
Extreme_Rotor_deflection1344×1046 85.1 KB

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

2

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,