Computational differences with ED+BD+ADv15 versus ED+ADv15

I need clarifications regarding the computational differences using ElastoDyn+AeroDyn_v15 and ElastoDyn+AeroDyn_v15+BeamDyn. I’m not understanding the differences occurred in the steady state values of the collective pitch u[/u] considering an isotropic blade modelled throught FAST with same mechanical properties using BeamDyn and ElastoDyn respectively. In particular, the simulation is performed using FAST+Simulink considering a steady wind with wind speed equal to 18 m/s, the turbine implied is a RWT 10MW DTU, the control strategy is based on collective pitch controller and torque controller; constant power output is the goal of the control strategy.

My personal guess about the explanation of the pitch difference between ED+ADv_14 and ED+ADv_15 model is that the modellation with ADv_14 and ADv_15 is not perfectly equal and the difference between the two might rise difference in output. This explanation doesn’t fit if we consider ED+BD+ADv15 and ED+ADv15, since I’m modelling the mechanical properties equally in both cases and the AeroDyn model is the same.
In particular the pitch difference is about 0.5 deg considering ED+BD+ADv15 and ED+ADv15.

I hope that someone could give me a more solid explanation to this situation.

Thanks in advance for your help.


Dear Simone,

I generally agree with your assessment of the differences between ADv14 and ADv15. Of course, the exact differences between these solutions will depend on the aerodynamic model options selected.

Between ADv15 and ADv15+BD, the biggest difference is likely related to the inclusion of blade-torsion degrees of freedom in the BeamDyn structural dynamics module, which are not included in ElastoDyn. Elastic twist often results in a change in the blade-pitch angle.

Best regards,

Thank you, your clarifications were really helpful.