Aeroacoustic investigation of leading edge erosion in a wind tunnel

Leading edge erosion (LEE) on wind turbine blades is a significant challenge for the wind turbine industry. It affects the structural integrity of the blades as well as the aerodynamic and acoustic performance. While there is a lot of research addressing structural integrity and aerodynamic performance, the effects of LEE on noise emissions remain largely unknown. The goal of this study is to analyze effects of LEE on the noise emission at airfoil level through wind tunnel testing. Aerodynamic and acoustic measurements were conducted on an FFA-W3-211 airfoil in the Poul la Cour wind tunnel at DTU Risø Campus, using various leading edge surface conditions to simulate erosion damage. Two wind tunnel configurations were utilized: hard walls for capturing aerodynamic lift and drag coefficients, and Kevlar walls for recording far-field noise with a microphone array. The combined dataset ranges from Reynolds numbers of 1.8 million to 4.5 million and angles of attack from -20 to +20 degrees, with four different leading edge surface conditions consisting of sandpaper and trip tape (zig-zag tape). The results indicate that in the attached flow regime there is a strong correlation between the measured drag and the acoustic noise emission. This suggests that the change in boundary layer properties due to an eroded leading edge is the primary driver of increased noise generation. A regression model describing the noise increase as a function of drag increase is derived. This methodology can serve as the basis for future investigations of leading edge erosion and may lead to new models for noise characterization.