This study employs molecular dynamics simulations using the momentum mirror method to investigate the collapse of nanoscale bubbles, focusing on the effects of bubble diameter (D), water molecular velocity (vw), and relative wall distance (γ). In cavitation processes, the mechanical effects are ultimately governed not only by the primary collapse of millimeter- or micrometer-scale bubbles but more critically by their secondary or repeated collapses that generate nanoscale daughter bubbles; however, the multi-factor coupled collapse behavior of such nanobubbles and their associated micro-erosion mechanisms remain insufficiently understood. The coupled influence of these parameters on the bubble collapse process and the subsequent erosion evolution on copper surfaces was analyzed, and a range analysis was applied to quantitatively assess the contribution of each factor. The results indicate that under the action of shock waves, nanobubbles collapse and generate high-speed nano-jets. When these nano-jets impinge on the copper surface, a water hammer effect is induced, producing an annular impact zone with local pressures ranging from approximately 21.00 to 34.52 GPa, leading to the formation of erosion pits on the material surface. The maximum pit depth reaches 8.920 Å. Range analysis shows that the relative influence of the factors on cavitation erosion follows the order D, vw, and γ. Moreover, under the combined effect of multiple factors, the surface roughness of copper rapidly increases due to the water hammer effect and eventually stabilizes as a result of pit overlap and work hardening, reaching a maximum roughness of 1.28 Å.
Li et al. (Thu,) studied this question.