Consistent 3D CFD and BEM simulations of a research turbine considering rotational augmentation

The present studies evaluate the importance of the three-dimensional (3D) effects in a research turbine blade by comparing the Blade Element Momentum (BEM) simulation results to the fully resolved 3D Computational Fluid Dynamics (CFD) computations. The turbine has a diameter of around 50 m producing a rated power of 750 kW and is designed to be erected at Stottener Berg in the southern part of Germany within the framework of the WINSENT (Wind Science and Engineering in complex Terrain) project. In the first part of the studies, 3D CFD simulations employing the URANS approach are performed for several pitch angles at a constant freestream inflow condition. The effective angles of attack are evaluated using two different approaches for 6 defined sections along the blade radius to extract the 3D polar characteristics. Then, the extracted 3D polar data are applied in the BEM simulations and compared to the results employing 2D polar with a 3D correction model in the second part of the work. The results show that the use of the 3D polar data improves the BEM prediction significantly while the 2D corrected polar data generate a strong deviation compared to the 3D CFD results.