AeroDyn V15 standalone forces compared to coupled Aerodyne Openfast forces ( RtAeroFxh RtAeroFyh RtAeroFzh)

Wind & Water Rotor Aerodynamics
1

Dear All,

I was hoping that somebody might be able to sense check some results for me. I have run two simulations with the aim of obtaining aerodynamic loads on the rotor.

The first simulation was run using OpenFast and RtAeroFxh RtAeroFyh RtAeroFzh RtAeroMxh RtAeroMyh RtAeroMzh (which I believe are given in the Hub Co-coordinate system) were obtained using a steady wind speed (WindType = 1) of 8.7 m/s.

The second simulation was run using Aerodyne standalone using AeroDyn Driver v1.00.x Input File. Again, RtAeroFxh RtAeroFyh RtAeroFzh RtAeroMxh RtAeroMyh RtAeroMzh were obtained.

I was hoping somebody could verify that the results I am seeing for each simulation are sensible? My main concern is that there is a big difference in the aerodynamic forces and associated moments in the y and z coordinates (please see the attached output files). I am struggling to understand why that is the case.

Any help would be much appreciated.
Test01.1_Aerodyne.txt (907 KB)
WP_VSP_WTurb_Openfast.txt (226 KB)
ad_driver_example.txt (1.64 KB)

2

Dear Benjamin,

You haven’t stated how your OpenFAST model is set up, but I would guess you have structural degrees of freedom enabled, whose oscillations are causing oscillations in the aerodynamic loads. I would suggest disabling all of the structural DOFs in the OpenFAST (in which case the OpenFAST results should match those of AeroDyn, assuming you’ve set up the rest of the model identically) and then systematically enable structural DOFs to see what is effecting the aerodynamic loads.

Best regards,

3

Dear Jason,

Thank you for the helpful response. The structural degrees of freedom were disabled; however, it turns out that the shaft tilt angle was causing the 1P oscillation in the Aerodynamic forces.

As the tilt angle was not the same the results from Aerodyne and OpenFast were not matching. I have rectified this and the OpenFAST results match those of AeroDyn.

Thank You