Hello forum members,
The default airfoils in “5MW_Baseline” is Cylinder 1, Cylinder 2, DU21_A17, DU25_A17, DU30_A17, DU35_A17, DU40_A17, DU30_A17 and NACA64_A17. I am trying to replace and use any symmetric airfoil for the wind turbine blade instead of the used in the example. I want to analyze the parameters such as Yaw, Pitch, Roll and other motions when the airfoil Is throughout of same airfoil. I would like to also run the flow in the reverse direction on this symmetric airfoil to check whether the parameters gives exactly opposite results. I am currently taking NACA 0021 as an example. I have tried replacing data of airfoil on airfoilname_coords.txt files in 5MW_Baseline->Airfoils folder. I am having following questions related to this:
- How to replace airfoils data (exa. Cylinder 1, Cylinder 2, DU21_A17, DU25_A17, DU30_A17, DU35_A17, DU40_A17, DU30_A17 and NACA64_A17) with just one symmetric airfoil for wind turbine blade to do analysis in OpenFAST?
- What are the other files and parameters which should be changed along with airfoil data for Aerodyn?
- I am using airfoiltools.com to get airofil.dat file for the NACA 0021 file. Where can I get CL, CD and Cm data for the same to use in .dat file?
- Do I also need to change the Servodyn or any other file when I change airfoil for the blade for analysis?
Here are my responses:
- You can always use one airfoil data file (
NumAFfiles = 1 in AeroDyn) if you want to use the same airfoil data at all stations. That said, even if the same airfoil is used across the entire blade, I would expect rotational augmentation (3D effects) to require the use of different airfoil data files anyway, assuming that you want to consider such effects. (It is generally recommended to apply rotational augmentation corrections to airfoil data in a pre-processing step using tools such as AirfoilPrep or AirfoilPreppy before using airfoil data within OpenFAST.)
- You should be able to change the airfoil data in AeroDyn without changing other inputs, unless you are reoptimizing the blade (chord, twist, mass/stiffness, controller gains, etc.) based on the updated airfoils.
- I’m not familiar with airfoiltools.com, but it sounds like it can generate the Cl, Cd, and Cm versus angle of attack data that you need? Often airfoil data from XFoil or wind tunnel experiments usually only covers low angles of attack, so the airfoil preprocessors (AirfoilPrep or AirfoilPreppy) can also be used to extrapolate such data to the full 360-degree range of possible angles of attack, which is often important to do before running OpenFAST simulations.
- Typically the gains used by the controller are tied to the aerodynamic performance curves of the rotor, so, if you are trying to capture those effects, than “yes”.
FYI: the airfoil coordinates (shape) are not used by AeroDyn, except for surface visualization purposes.