Aerodynamic Force of Parked WP 1.5 MW

Wind & Water Rotor Aerodynamics
1

Dear Jason，
I got a problem in simulating the parked turbine. I used Test13（WP 1.5 MW）. I disabled all DOFs and I also set NacYaw=0，Azimuth=270，BlPitch(1)、(2)、(3)=90. I set WindType=1（steady），HWindSpeed=30. After running，drag force(RtAeroFzh)=-81900N,lift force(RtAeroFxh)=244.9N.

I also estimated the mean wind load on blades with Matlab. The drag force and lift force on each blade element per unit length is calculated as FD=0.5ρ(U^2)CD; FL=0.5ρ(U^2)CL. In this way，drag force is about -81091N(agree well with OpenFast)，lift force is about -8663N.

I checked CD and CL in OpenFast and MATLAB，they agree well. I don’t know why the lift force differs so greatly.But I think the lift force from OPenFast seems too little. Do you think the result from OpenFast credible？

Sincerely

2

Dear Chenxu.Zhao,

I’m not aware of any bug in the calculation of the rotor aerodynamic forces calculated and output from AeroDyn.

Perhaps this is just terminology, but given that the x-axis is along the shaft, I would call RtAeroFxh the drag force and the lift force would be in the y-z plane, at least for flow along the shaft. But because the WindPACT 1.5-MW has shaft tilt (ShftTilt = -5 in ElastoDyn)), flow will not be along the shaft, but would instead have some skew, so, lift and drag will not be along x, y, or z.

In your equation of the local per unit length value of lift and drag, presumably U includes all of the geometry involved (tilt, twist).

Best regards,