Steady state operating points for the WindPACT 1.5 MW model

Good morning,

I am working on the NREL WindPACT 1.5 MW turbine on openFAST, and I have a couple of queries regarding the steady state operating points for this model.

I am trying to implement a BEM code on python, and compare it with the BEM output from openFAST. I am running the standalone AeroDyn driver to obtain aerodynamic parameter values like Cl, Cd, P_aero, etc. In the AeroDyn driver input file, there is a section to specify the operating points at which aerodynamic analysis is run. Under WndSpeed (m/s) I am giving 4 to 25 m/s in steps of 1 m/s, and I am having some confusion in the RotSpd and Pitch columns.

I ran openFAST steady state simulations in this wind speed range, with the AeroDyn and InflowWind parameters as follows-
WakeMod = 1 (BEMT), AFAeroMod = 2 (Beddoes-Leishman unsteady model), SkewMod = 2 (Pitt-Peters) and WindType = 1 (steady) with 22 InflowWind files from 4 to 25 m/s. I ran the simulations for 200 seconds to get past the initial transient conditions and to allow the values to settle down. From the steady state simulation results, I took the values of RtSpeed and BldPitch1 when they settled down, at different wind speeds and noted them down as RotSpd and Pitch in the AeroDyn driver input file.

I ran the standalone driver with the same AeroDyn input parameters as mentioned earlier, and I obtained the values of RtAeroPwr from 4 to 25 m/s. I was getting aerodynamic power in excess of 1.5 MW after 12 m/s, and I was not able to figure out why this was the case. I would be very grateful if someone could shed some light on this.

Out of curiosity, I decided to compare the operating points I obtained as explained earlier with the steady state operating points as mentioned for the 1.5 MW model on the HAWC2 website, and found some differences in the values. I tried running the standalone driver with these operating points instead, and the aerodynamic power did not cross 1.3 MW, it reduced after hitting rated speed! Would someone be so kind as to explain why this is happening?

I am attaching the operating points I obtained from steady state openFAST simulations and the steady state operating points given on the HAWC2 website, along with the RtAeroPwr using both sets of operating points.

Thanks in advance,

Best regards,
Vishal Sairam

Dear Vishal,

The aerodynamic power from AeroDyn should exceed the electrical power of 1.5-MW because of losses in the aerodynamic to mechanical and mechanical to electrical conversion (the controller is regulating to 1.5-MW of electrical power).

The standalone AeroDyn driver will also give a bit different answers than the OpenFAST simulation if structural degrees of freedom are enabled in the OpenFAST model (especially blade deflection).

Regarding the results from HAWC2, I’m not sure. I would guess there is some difference between the aero-elastic model definition and/or controller between the OpenFAST and HAWC2 models.

Best regards,