## Extract blade tip torsional deformation from the Wiener-Milenković parameters in BeamDyn

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Xiaoqi.Qu
Posts: 4
Joined: Thu Dec 06, 2018 1:51 am
Organization: Tianjin University
Location: China

### Extract blade tip torsional deformation from the Wiener-Milenković parameters in BeamDyn

Dear all,

I am trying to extract the blade tip torsional deformation from the outputs of BeamDyn. The parameters "TipRdxr", "TipRDyr" and "TipRDzr" in BeamDyn output are Wiener-Milenković rotation parameters, which corresponds to c1, c2 and c3 in the equation(5.17) in BeamDyn User's Guide. Now I can calculate the rotation tensor R(c), and then extract the Euler angles (yaw, pitch and roll) from it. My question is that the Euler angle which represents the rotation around the blade pitch axis is the blade torsional deformation?

Best regards.
Xiaoqi

Simon.Wiedemann
Posts: 75
Joined: Mon Jan 09, 2017 1:00 am
Organization: TÜV NORD
Location: Germany

### Re: Extract blade tip torsional deformation from the Wiener-Milenković parameters in BeamDyn

Hi Xiaoqi,

had you been able to calculate the blade tip torsional displacement in BeamDyn?
I have right now the same task.

Best regards,
Simon

Simon.Wiedemann
Posts: 75
Joined: Mon Jan 09, 2017 1:00 am
Organization: TÜV NORD
Location: Germany

### Re: Extract blade tip torsional deformation from the Wiener-Milenković parameters in BeamDyn

Hi all,

is it correct that the Theta-angle (Inflow) that is available as output in AeroDyn can give the rotational deflection about blade root z-axis when substracted with the fixed aerodynamic twist and the time dependent pitch angle?

So:
Rotational deflection = Theta at node - aerodynamic twist at node - pitch angle of blade

Best regards,
Simon

Jason.Jonkman
Posts: 5763
Joined: Thu Nov 03, 2005 4:38 pm
Location: Boulder, CO
Contact:

### Re: Extract blade tip torsional deformation from the Wiener-Milenković parameters in BeamDyn

Hi Simon,

I had has asked someone else from NREL to respond to Xiaoqi's original post, and I don't see that they have.

I'm not sure I fully understand how twist/torsion is defined for a curved or deflected blade (it is trivial for a straight undeflected blade). I would guess the actual twist would have to be defined by integrating the local incremental twist around the local z-axis of the blade (tangent to the curve) from the root to each cross section. I had asked for confirmation on this from others at NREL, but I have not yet received a response.

The Wiener-Milenkovic parameters output from BeamDyn define the actual orientation of each cross section relative to the undeflected orientation.

Likewise, the theta angle output from AeroDyn gives the actual orientation of the airfoil (chordline) relative to the local AeroDyn blade coordinate system (the rotation about the local z axis), which is tangent to the deflected blade in the out-of-plane deflection.

Based on my understanding of twist/torsion above, neither the Wiener-Milenkovic parameters nor theta will result in the actual twist, except for straight undeflected blades, although for curved / deflected blades, these angles will be reasonable proxies for the actual twist.

Bet regards,
Jason Jonkman, Ph.D.
Senior Engineer | National Wind Technology Center (NWTC)

National Renewable Energy Laboratory (NREL)
15013 Denver West Parkway | Golden, CO 80401
+1 (303) 384 – 7026 | Fax: +1 (303) 384 – 6901
nwtc.nrel.gov

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