A case study on the calibration of the k-ω SST (shear stress transport) turbulence model for small scale wind turbines designed with cambered and symmetrical airfoils

This work presents a calibration study of the k-ω SST turbulence model for small scale wind turbines. To accomplish this, two different sets of blades were designed, built, tested and simulated. The first set applied the NACA 0012 and the second the NACA 4412 airfoil. The numerical investigation was taken using the CFD (computational fluid dynamics) code OpenFOAM and the turbulence model was calibrated testing several values for the β∗, including its canonical value, 0.09. The numerical calibration (the main contribution of this paper), extended previous results, which stated that different β∗ values could calibrate the k-ω SST turbulence model for small wind turbines, mainly for the drag effects. The study broadened this conclusion, once the model was calibrated for a quite wide range of tip speed ratio values, from the turbine startup (λ = 0) until its highest experimental value (λ ≅ 8). As a secondary contribution, the results show that the model could be adjusted to simulate average field data, even though these being subject to its inherent variabilities. The main conclusion was that, for the sets of blades studied, the lowest RMSE value was obtained for β∗ = 0.27.