Review: Fundamentals of liquid droplet impingement and rain erosion of wind turbine blade

Leading edge erosion of wind turbine blades is a critical concern in the advancement of offshore wind turbines for power generation. This study reviews the fundamentals of liquid droplet impingement and leading edge erosion in wind turbine blades operating under rainy conditions. A central focus is on the role of peak impact pressure from droplet collisions on dry and wet walls, which significantly contributes to erosion initiation of wind turbine blades. Factors influencing this phenomenon, such as erosion initiation mechanism on metallic material, liquid film thickness, surface roughness, and droplet temperature, are analyzed to elucidate the physical mechanisms of erosion initiation in metallic materials. Furthermore, attention is paid to the prediction of erosion initiation on an actual wind turbine blade using a whirling-arm ground tester on wet wall, where the influence of the liquid film thickness on erosion initiation has to be corrected due to the scale effect of the blades.