Numerical study on the shock-induced ejecta formation from a grooved aluminum surface: The effect of groove size

The structure of surface defects is one of the primary focuses in exploring the mechanism behind microjetting phenomena. However, the influence of defect size on microjets remains understudied. This work investigated the correlation between shock-induced microjets and surface defect scales under continuous approximation with the smoothed particle hydrodynamics method. The physical properties of microjets from generation to fragmentation were analyzed in detail. A relationship between the mass of different parts of the microjet and the defect size was established. The results indicate that the length of microjets and the jetting head velocity increase with the increase in the defect sizes. The jetting head velocity increases significantly when the defect depth is less than 4 μm, and the increase slows down when the defect depth is greater than 4 μm. This is attributed to the pressure and energy variations in the defect surface layer. A transition in the mass distribution of the microjet occurs when the defect depth reaches 7 μm. The jetting factor exhibits a trend of decreasing first and then increasing with the enlargement of defect size. The time of microjet fragmentation shows a proportional relationship with the defect size. By statistically analyzing the distribution of microjet fragmentation aggregates, it is found that the dispersal degree of microjet fragmentation aggregate sizes increases with defect size. This research reveals the correlation between the microjet and defect size.