Post-fix validation — remaining differences vs RAFT reference (bending, surge, etc.)

[SevenSky777]

Hi,
The order-of-magnitude error has been resolved using the dev branch, which is great progress. However, when comparing the results to the RAFT reference paper I still see notable discrepancies—not only in bending moment but also in surge and other response components. I’ve attached a few screenshots for reference. Let me know if you need any additional context or if there’s anything else I should cross-check.

[lucas-carmo]

My apologies, the fix I pushed yesterday was computing the moment wrt the wrong location. I pushed another fix, could you please try again? The results won't be the exact same as in that paper because both RAFT and the IEA15MW changed in the meantime.

As a heads up, the current method to compute the tower bending moment is temporary. It should have been replaced in v2.0 but that got postponed. We plan to have something more robust as soon as possible :D

[SevenSky777]

Thanks for your prompt attention!
Correct me if I’m wrong, but based on the current implementation, the aerodynamic force/moment is applied at the rotor-turbine interface, which should correspond to "Zhub" or a close value like "self.rotorList[ir].nodeList[0].r0[2]".
However, the arm used for the aerodynamic moment is currently defined as hArm[ir] = zCG_turbine[ir] - zBase[ir], where "zCG_turbine[ir]" refers to the center of gravity of the combined turbine and tower—not the turbine alone. This introduces a discrepancy.
To correct this, the moment at the base (Mbase) should be computed as:
results['Mbase_avg'][ir] = (
m_turbine[ir] * self.g * hArm[ir] * np.sin(self.Xi0[4]) +
transformForce(self.rotorList[ir].f0, offset=[0, 0, self.rotorList[ir].nodeList[0].r0[2] - zBase[ir]])[4]
)
I validated this using two approaches:

Route A: transformForce from hub to base
f0_hub = self.rotorList[ir].f0
hub_z = self.rotorList[ir].nodeList[0].r0[2]
My_base_A = transformForce(f0_hub, offset=[0.0, 0.0, hub_z - zBase[ir]])[4] + m_turbine[ir] * self.g * hArm[ir] * np.sin(self.Xi0[4])

Route B: analytical shift via cross product
deltaMy = f0_hub[0] * (hub_z - zBase[ir])
My_base_B = f0_hub[4] + deltaMy + m_turbine[ir] * self.g * hArm[ir] * np.sin(self.Xi0[4])

I’m looking forward to a robust implementation, and I hope other force and moment components will be added.

[SevenSky777]

In my view, the final moment at the tower base should also account for the x‑coordinate of the center of gravity of the combined turbine and tower:

Turbine center of gravity in x-direction

xCG_turbine[ir] = ( self.rCG_tow[ir][0] * self.mtower[ir] + rotor.xCG_RNA * rotor.mRNA) / m_turbine[ir]

Updated Mbase calculation

results['Mbase_avg'][ir] = (m_turbine[ir] * self.g * (xCG_turbine[ir] + hArm[ir] * np.sin(self.Xi0[4]))
+ transformForce(self.rotorList[ir].f0, offset=[0, 0, self.rotorList[ir].nodeList[0].r0[2] - zBase[ir]])[4])