Influence of surface roughness on liquid droplet impingement erosion

In this paper, liquid droplet impingement (LDI) erosion on the groove roughness of aluminum (A1070) is studied both experimentally and numerically, to understand the erosion mechanism on rough surfaces. The experiments are carried out using spray-jet erosion apparatus. The erosion rates on two kinds of roughness (W and V grooves) are measured, and the erosion patterns are observed using a scanning electron microscope (SEM). An early erosion is observed on the W groove in comparison with the V groove, which is caused by removal of the groove peak. The SEM observations show that the erosion initiates from the groove trough of the W groove and intrudes into the lower side of the groove peak, which is followed by the removal of the groove peak. Furthermore, numerical simulation is carried out for a single droplet impingement on the W groove to explain the physical mechanism of early erosion from the point of impact pressure distribution on the grooves. It is found that the shock wave loading at the groove peak generates high impact pressure on the peak, while the focused shock wave generated by droplet impact on the groove trough and middle generates a similar magnitude of pressure impact on the trough. This corresponds to continual pressure impacts on the groove trough, and results in an increased erosion rate on the W groove roughness.