A model for evaluating the amplitude of pressure wave impacts generated by the collapse of bubble cluster near a solid wall

Cavitation-induced erosion in underwater structures is primarily attributed to the high pressures generated during the collapse of cavitation bubbles. To explore the mechanisms of these pressure impacts, this study presents a detailed three-dimensional numerical study on the collapse of bubble clusters near a solid wall and put forward a model for the pressure wave impact evaluation. Simulations are performed on the OpenFOAM platform utilizing a direct numerical simulation approach. The Volume of Fluid (VOF) method is employed to accurately capture the interface between the two phases. The results show that the collapse of bubble clusters near the wall displays an asynchronous layer-by-layer collapse pattern. The wall is subjected to several pressure wave impacts, with the most significant arising from the pressure wave released after the complete collapse of the bubble cluster. The jet also impacts the wall when the standoff distance γ c is small enough. At high vapor volume fractions, parametric studies reveal that the pressure wave impact induced by 5-layer bubble clusters is independent of the radius of the internal bubbles R 0 , and increases exponentially with driving pressure Δ p 0 . 5 ∼ 0 . 6 . Within the range of γ c = 1 ∼ 3 , the pressure wave impact can be considered proportional to γ c − 1 . 6 ∼ − 1 . 5 . And the pressure wave impact increases linearly with volume fraction α v when α v > 0.238. We derived a theoretical formula for evaluating the amplitude of the pressure wave impact during bubble cluster collapse through the energy conversion mechanism. Moreover, The arrangements in dense spherical clusters have little effect on pressure wave impact at large stand-off distances, but become considerable when the cluster is very close to the wall, especially in sparse clusters. The geometric symmetry of bubble clusters may also exert a significant influence on the pressure wave impacts. This study can provide valuable insights for predicting cavitation damage for engineering applications. • Analyze asynchronous layer-by-layer collapse and flow field of near-wall bubble clusters. • Reveal the effects of multiple parameters on pressure wave impact of bubble clusters. • Develop a theoretical model to evaluate pressure wave impacts under various conditions. • Investigate influence of bubble cluster arrangement and shape on pressure waves.