Airfoil Profile Coefficients

Wind & Water Airfoils
1

Hello Everyone

I attended FAST conference at EWEA offshore Conference in Frankfurt last month, it was very informative. I am looking forward for get deeper into aeroelastic simulations using FAST.

I have a question regarding the aerodynamic Profile coefficients of the rotor blades used in the aeroelastic simulations. I would really appreciate if you can answer me this question.

I know that usually in big wind turbines , they either use standard NACA/DTU/FFA-W airfoils and they have well documented experimental values for the Profile coefficients such as coefficient of lift, drag and moment coefficient.

In my case the rotor blades are designed completely by a professional External CFD company.

I received the new rotor blade profiles now requires the rotor blade profile coefficients.

I did some research regarding the different ways of retrieving the Profile coefficients for different Angle of Attack.

  1. Wind tunnel tests: (Being a very small start up, it is not possible for our company at the moment due to economic constraints).
  2. 2D CFD simulation done using a commercial software like ANSYS by me .
  3. 2D CFD simulation done at an external professional CFD company( cost atleast 5000-10000 Euros)
  4. A 3D CFD simulation which can be very expensive.

I found that the codes like XFoil, Java Foil, Qblade, etc are not stable enough at high angles of attack.

I am wondering whether we go for the certification process later, which method of finding the Profile Coefficients is the most accepted way?

If i do it in an External Certified CFD professional company, is the values directly being accepted ?

If I am doing it myself, how can I show that the simulation is valid later?

I would be very thankful if you can answer these questions to me.
.

Thank you very much

Regards

Sudheesh

2

Dear Sudheesh,

I’m not an aerodynamicist and am not very familiar with the CFD methods you mentioned. This is not something we do ourselves here–we’ve always hired experts to use computation methods or we’ve done wind tunnel tests.

If I had to do this on a tight budget, I’d be inclined to use XFoil to generate the pre-stall data and then maybe use AirfoilPrep to fill in data using either flat-plate theory or the Viterna Method. Even if I were to pay extra for professional help with more-sophisticated methods, I’d probably use Xfoil just as a sanity check.

3

Thank you very much for your reply. I guess, I will have to hire experts for wind tunnel tests. I have used XFoil data for aeroelastic simulation as a part of my master thesis, the final results were not satisfactory. Blades being the most important part in the simulation, I believe 2 D wind tunnels test will be required at some point of the certification stage, its better to do it now.

Thank you very much

Regrads

Sudheesh Sureshkumar
ss@enbreeze.com