NREL subroutines vs CFD/FEA

I have recently become involved with the wind turbine design industry. So far it seems that most of the wind turbine companies certify their products based on the IEC 61400-1 standard. As well it seems that NREL in collaboration with other organization have developed over the years subroutines (Turbsim, Aerodyn, FAST, etc…) to investigate and analyze the structural dynamic loadings induced by different wind load models.

This question might seem easy for some of you but what are the advantages of using this methodology over a bi-directional or Fully Coupled multi-physics approach (in other words a commercial CFD code coupled with a commercial FEA code such as the ANSYS platform)? Is this multi-physics approach valid for IEC certification? wouldn’t you get more information by solving the N-S equations instead of using the BEM theory?

Looking forward to your answers…

Dear Andres,

CFD and FEA have their uses, but such a coupled aero-hydro-servo-elastic solution is simply too computationally intensive to be relied upon as the sole tool for running the thousands of load case simulations (with various combinations of environmental conditions and operational behaviour of the turbine´s control and protection system) dictated by IEC-based design requirments.

Neither are CFD and FEA foolproof. Wind turbine aerodynamics requires careful consideration of the various flow phenomena: turbulent inflow, unsteady aerodynamics, wake effects, array interaction, etc. that are not trivial to resolve using CFD. Wind turbine structural dynamics requires careful consideration of the rotory dynamics: inertial, centrifugal, coriolis, and gyroscopic, etc. forces that are not trivial to resolve using FEA.

Best regards,


I really appreciate your input in this post. I believe that you have been quite involved in the analysis of HAWTs. The reason of me asking this sort of question is that I am currently researching options of available codes or applications to analyze the aero-elastic behavior of VAWTs. Unfortunately, the codes available from NREL are application specific to the analysis of HAWTs.

I have contacted other laboratories and organizations (e.g. SANDIA) to identify if there are current codes available for this type of turbines but the results have not been favorable. If you don’t mind me asking, what approach would you recommend taking to analyze the aero-elastic behavior of VAWTs? The generation of a new code to study this behavior for the different models shown in the IEC will be a steep effort from a resource and time perspective.



Dear Andres,

To my knowledge, there is no code similar to FAST with AeroDyn that can model the aero-elastic dynamics of VAWTs. I believe Sandia had some old aerodynamics codes for VAWTs, but I don’t believe they incorporated structural dynamics.

You may wish to contact research staff at the Technical University of Delft in the Netherlands, who do currently have an active research program on VAWTs.

Best regards,