Numerical Investigation of Curvature-ratio Effects on Cavitation Bubble Collapse Dynamics under Different Wall-gap Conditions

Predicting cavitation erosion in particle-laden hydraulic machinery requires a comprehensive understanding of bubble collapse influenced by the interaction between particle and wall confinement. However, the specific roles of particle curvature and wall gap in modulating jet and pressure responses remain unclear. In the present study, three-dimensional volume-of-fluid simulations are conducted using the compressibleInterFoam solver in OpenFOAM to investigate a single bubble within a coupled bubble-particle-wall system. With the initial bubble diameter held constant, the effects of six curvature ratios (κ=1.0-1.5) and two gap ratios (ζ=1.0 and 0.9) on the results are methodically examined. An increase in κ is found to amplify the particle radius and reduce the particle-surface curvature, consequently weakening liquid convergence toward the bubble axis. This shift in dynamics leads to a transition from strong non-spherical jet penetration to more uniform volumetric contraction during collapse, resulting in an overall decrease in peak bubble-center velocity. The pressure response exhibits a distinct trend; specifically, at ζ=1.0, peak pressure decreases with increasing κ. At ζ=0.9, however, it demonstrates non-monotonic variation, influenced by the timing of wall-reflected waves and secondary compression of the residual gas phase. These results highlight that jet velocity alone is insufficient for characterizing local impact intensity in such systems. Therefore, it is critical to consider both curvature ratio and gap ratio in assessing cavitation-erosion risks for particle-laden near-wall flows.