Investigation of Riblet Effects on the Surface Roughness Induced Performance Loss of Wind Turbine Blades

As wind turbine adoption has increased, leading-edge erosion (LEE)—damage to the leading-edge of turbine blades—has emerged as a significant factor in reducing power output efficiency and increasing maintenance costs. Leading-Edge Protection Tape (LEPT) is effective as a countermeasure against LEE; however, the step formed by LEPT can also cause aerodynamic losses. In this study, we propose riblets as a means to mitigate the adverse effects of leading-edge surface roughness—resulting from LEE, LEPT, and similar factors—on the aerodynamic performance of wind turbine blades, and evaluate their effectiveness through wind tunnel tests. The MEL18M31 airfoil was used in the wind tunnel tests, and surface roughness was introduced by attaching zigzag-shaped wires to the leading-edge of the airfoil. First, under conditions without attached wires, it was confirmed that the application of riblets improved the lift-to-drag ratio by an average of 10.7% over the angles of attack range from 0–10°. In contrast, when a small wire (0.3 mm thick, 5 mm wide) was attached to the leading-edge, the lift-to-drag ratio decreased by an average of 14.2% without riblets, but increased by an average of 15.2% with riblets in the same angle of attack range. These results suggest that riblets not only improve the aerodynamic performance of wind turbine blades, but also mitigate the deterioration caused by leading-edge surface roughness.