During their operation, wind turbine blades are eroded due to rain and hail, or they are contaminated with insects. Since the relative inflow velocity is higher at the outer than at the inner part of the blades, erosion occurs mostly at the outer blade region. In order to prevent strong erosion, it is possible to install a leading edge protection, which can be applied to the blades after the initial installation, but changes the shape of the initial airfoil sections. It is unclear how this modification influences the aerodynamic performance of the turbine. Hence, it is investigated in this work. The NREL 5 MW turbine is simulated with clean and eroded blades, which are compared to coated blades equipped with leading edge protection. Aerodynamic polars are generated by means of Computational Fluid Dynamics, and load calculations are conducted using the blade element momentum theory. The analysis in this work shows that, compared to clean rotor blades, the worse aerodynamic behaviour of strongly eroded blades can lead to power losses of $9\%$ . In contrast, coated blades only have a small impact on the turbine power of less than $1\%$ .

The aim of this work is to investigate the capabilities of current engineering tools based on Blade Element Momentum (BEM) and free vortex wake codes for the prediction of key aerodynamic parameters of wind turbines in yawed flow. Axial induction factor and aerodynamic loads of three wind turbines (NREL VI, AVATAR and INNWIND.EU) were investigated using wind tunnel measurements and numerical simulations for 0 and 30 degrees of yaw. Results indicated that for axial conditions there is a good agreement between all codes in terms of mean values of aerodynamic parameters, however in yawed flow significant deviations were observed. This was due to unsteady phenomena such as advancing & retreating and skewed wake effect. These deviations were more visible in aerodynamic parameters in comparison to the rotor azimuthal angle for the sections at the root and tip where the skewed wake effect plays a major role.

This manuscript presents an effort towards the introduction of a new grid generation tool for computational fluid dynamics (CFD) simulations of wind turbines. The tool was developed and designed to considerably reduce the duration and complexity of the grid generation process and, moreover, to enable users to perform an efficient CFD simulation for a complete wind turbine rotor. Furthermore, the tool is fully automatized, thus enabling the user to refine the grid along the desired direction. For the purpose of validation, the quality of the generated grid was checked via a grid independence test. Finally, the grid generator tool was evaluated by means of a series of simulations of the NREL phase VI rotor using a three-dimensional CFD Reynolds averaged Navier–Stokes method. The capability of CFD simulations based on the generated grid in capturing aerodynamic performances (such as the power) and the detailed flow characteristics (e.g. the surface pressure distributions) were investigated under various conditions. The obtained results demonstrate the quality and reliability of the developed grid generation tool.