Numerical investigation of surface roughness sensitivity for different wind turbine airfoils

Prolonged operation of wind turbines leads to blade contamination and erosion, increasing surface roughness and significantly degrading aerodynamic performance. This study employs two-dimensional steady Reynolds-Averaged Navier-Stokes (RANS) simulations to evaluate the impact of surface roughness on DU, FFA, and NACA airfoils across various thicknesses. Traditional roughness models often oversimplify geometries, so a roughness strip is introduced to simulate realistic erosion patterns on the airfoil surfaces. Coupled with the γ -Re θ transition SST model, the present simulations effectively capture boundary-layer transitions and flow separation, yielding more accurate results. The results indicate that roughness impacts are highly dependent on the airfoil type and thickness. For the same thickness, blunt trailing-edge airfoils exhibit greater resistance to roughness effects; the NACA-63430 airfoil experiences a 35% reduction in maximum lift and a forward shift of 4° in stall angle due to surface roughness. Conversely, the DU97-W-300 airfoil only shows a 27% decrease in maximum lift and a stall angle shift forward of 2°. In general, thin airfoils exhibit greater flow stability and less sensitivity to roughness compared to their thick counterparts. Furthermore, as the Reynolds number increases, the negative effects of surface roughness on the airfoil are diminished.