Simulations for Effect of Surface Roughness on Wind Turbine Aerodynamic Performance

In the present study, blade surface roughness effects on the aerodynamic performance of NREL Phase VI wind turbine rotor are investigated using Reynolds-Averaged Navier-Stokes (RANS) simulation. The rotating rotor component is modeled using an overset mesh system and computations are conducted using an in-house heterogeneous CFD framework based on both CPUs and GPUs. The effect of laminar-turbulent boundary layer transition on the blade is included using the γ – $\overline{R{{e}_{\theta t}}}$ – SA model. The surface roughness effects on both the turbulent boundary layer and boundary layer transition are modeled through extensions of turbulence and transition models. The locally distributed roughness at the leading edge zone is applied for both S809 airfoil and NREL Phase VI rotor simulations. The roughness effects on the airfoil performance are captured, and the prediction shows reasonable agreement with the experimental data. In the case of the rotor simulation, the surface roughness affects the performance differently depending on the wind speed. At the operating wind speed with attached flows, the roughness decreases the performance due to the roughness-induced transition occurring at the leading edge. On the other hand, at the higher wind speed, this transition induces less flow separation on the leeward side of blade, which is favorable to the performance. As the wind speed increased further, the flow become fully separated and the roughness effect is minor.