Pulsating water jet for accelerated rain erosion of blade coatings: effects of process parameters and coating elasticity, with performance compared to whirling arm rig data

Pulsating water jets attract increasing attention for fast screening of rain erosion properties of wind turbine blade coatings. However, compared to natural rain erosion, the difference in experimental conditions adds significant uncertainty to the test results. The present work investigates the effects of impact velocity, exposure time, substrate type, coating elasticity, and impact frequency on the coating erosion process in a high-frequency pulsating water jet. Measurements were compared to data from a whirling arm rig, which, for decades, has served as the industrial standard. For four coating systems, it was shown that to initiate the erosion process, certain water jet threshold velocities are required. Furthermore, under high-frequency impacts, the effects of steel and glass fiber-reinforced epoxy resin substrates, relative to other process parameters, proved insignificant for the erosion process. For elastic coatings, the water jet erosion rate was notably affected by the impact frequency, with high-frequency impacts in the pulsating water jet resulting in a much faster erosion process in elastic coatings than in rigid (stiff) coatings. Variations in experimental conditions, especially the impact frequency, resulted in different coating failure sequences in the pulsating water jet and the whirling arm rig.