Eigenfrequencies of IEA-15-240-RWT-Monopile Blade & Full System

Dear NREL Team,

I am currently modeling the IEA-15-240-RWT-Monopile in Simpack. In order to validate the rotor blade I compare the Eigenfrequencies from Simpack with data from


and also from natural frequencies from linearization run with OpenFAST.

While there is good agreement of the full system Eigenfrequencies with OpenFAST, the blade edgewise natural frequencies differ up to 15 % from those two papers. The flap-wise are in good agreement.

According to the release notes you updated the mass and stiffness properties in v1.1.

Was this update after the publication of those two papers?

And if so, do you have also the new natural frequencies of the blade with the updated properties you could share?

With kind regards


Hello Markus,
I’m really sorry, the notification about your post slipped through my emails. Jenni Rinker and I did a lot of work to align OpenFAST and HAWC2 models. We have a draft publication describing all our work, but unfortunately we’re delayed by some erratic behavior in OpenFAST that we must resolve before finalizing the results.
This said, the two models currently in the master branch of the IEA15 repo match well in terms of elastic frequencies and structural damping. Tower and rotor edge frequencies and damping still match reasonably well when aero is included, but rotor flap differs significantly. So far we haven’t been able to explain this discrepancy. Also, we’ve focused only on the system above the water line. Unfortunately we don’t have the comparison for the turbine on top of the monopile.
I copy below some plots, hoping that to help. Solid lines come from OpenFAST, dashed from HAWCStab2.
Best regards,

Rotor only

Turbine elastic - Clamped at tower base and with HAWCStab2 tower artificially stiffened in torsion

Turbine aero - Clamped at tower base