A comprehensive study of the impact pressure induced by a single cavitation bubble collapsing near a solid wall

We conduct a comprehensive investigation into the wall impacts induced by a single cavitation bubble collapsing near a solid wall, combining numerical simulations with theoretical analysis. We classify the modes of wall impact into three categories based on the standoff distance, γ: pressure wave impact, jet stagnation impact, and water hammer pressure impact. Our findings reveal that the pressure wave impact remains unaffected by the initial radius R0 of the bubble, exhibits a proportional relationship with the square root of the driving pressure Δp, and inversely correlates with γ. We then derive a theoretical expression for the pressure wave impact by drawing insights from energy conversion principles. The jet stagnation impact, on the other hand, is directly proportional to Δp as well as the square of a polynomial involving γ. By quantifying the velocity of the jet impact based on its formation mechanism, we obtain theoretical expressions for both the jet stagnation and water hammer pressure impacts. In accordance with the specific ranges of occurrence and magnitude distribution for each type of impact, we propose the ultimate impact prediction model. When γ>1.97, the predominant source of maximum impact pressure on the wall is attributed to the pressure wave impact, reaching magnitudes of 106 Pa. For γ values ranging from 1.73 to 1.97, the principal contributor to the maximum impact pressure on the wall shifts to the jet stagnation impact, reaching levels of 107 Pa. Conversely, when γ≤1.73, the predominant cause of maximum impact pressure on the wall is the water hammer effect, with magnitudes reaching 108 Pa. This study provides a novel perspective on analyzing the mechanics of wall impacts during the collapse of a cavitation bubble near a solid surface, and the developed models offer valuable insights for predicting and mitigating cavitation erosion.