In-plane and out-of-plane displacement results

Wind & Water Structural Analysis
1

Hello,

I’m trying to obtain the same tip displacement presented in the NREL 5 MW report for both the flapwise and edgewise directions. I’m using the Actuator-Line method with a beam model.

For the out-of-plane direction, I obtained similar results at 11.4 m/s. However, for the in-plane direction, I obtained -0.2 m (compared to approximately -0.6 m in the report).

I would like to know which force is used as input in FAST to compute the in-plane deformation (I used the tangential force). Also, are the structural properties referred to as “EdgStff” and “EdgIner”? Because when I’m using “FlpStiff” and “FlpIner” with the tangential force as input, I obtain similar result for the in-plane displacement.

2

Dear @Enzo.Mascrier,

Just a couple comments:

  • Given the structural pretwist of a wind turbine blade, both the normal and tangential aerodynamic forces give rise to the flapwise and edgewise (or out-of-plane and in-plane) deflections. Does your beam formulation consider the effects of structural pretwist?
  • I would not expect the cross-sectional inertias to play much role in deflection of blades with high aspect ratio.

Best regards

3

Dear @Jason.Jonkman

My beam formulation takes into account the pretwist. Something I forgot to ask on my previous question, does the gravitationnal force is considered in the NREL 5 MW report ?

Best regard

4

Dear @Enzo.Mascrier,

If you are referring to Figure 9-1 from NREL/TP-500-38060, gravity was included in these simulations, but I would not expect gravity to effect the mean blade deflection reported in this Figure. (Cross-sectional inertias should also not effect mean deflection.)

With the structural pretwist and much higher edgewise stiffness compared to flapwise stiffness, I would expect flapwise deflection to have much more effect on in-plane deflection than edgewise deflection would have on out-of-plane deflection. So, if your issue is with in-plane deflection, this could be the result of edgewise stiffness or edgewise loading, flapwise stiffness or flapwise loading, or the structural pretwist that couples the two.

Best regards,

5

Dear @Jason.Jonkman

Thank you for your quick answer, I’ll investigate on these potential issues.

Best regards,