Impact of trailing edge cracks on the aerodynamic performance and noise of offshore wind turbine airfoils

The blades of offshore wind turbines often experience trailing edge cracking after being struck by lightning, thereby affecting the aerodynamics and safety of turbines. A numerical simulation was used to analyze the effects of trailing edge crack (TEC) height and depth on the S809 airfoil's aerodynamic performance and flow field and to compare the changes in noise and vortex structures for airfoils with different levels of cracking, providing insights into the underlying mechanisms. The findings reveal that TECs do not affect the stall angle of attack but significantly degrade aerodynamic performance before the stall. Large crack heights lead to further reductions in performance, while the effect of crack depth is comparatively minor. TECs result in a substantial reduction in aerodynamic noise. As crack height grows, the extent of noise reduction diminishes, whereas increasing crack depth results in more significant noise reduction. Before and after the occurrence of TECs, the radiated noise of the airfoil exhibits a dipole distribution pattern. TECs disrupt vortex structures at the trailing edge, causing vortex fragmentation. As the vortices develop downstream, their strength diminishes further, and inter-vortex disturbances decrease, ultimately leading to a significant reduction in aerodynamic noise.