Investigation of vortex dynamics and effects on a wall induced by a cavitation bubble near a hemisphere on the wall

Cavitation-induced damage in hydraulic machinery is primarily caused by bubble collapse that generates high-speed jets and vortex structures. The present study employs a compressible two-phase flow model and a third-generation vortex identification method to analyze bubble dynamics near a wall with a hemispherical protuberance. The conclusions are as follows: (1) The distance between the bubble and the apex of the hemisphere critically influences bubble oscillation and vortex evolution, with a vortex typically forming near the hemisphere–wall junction. (2) Vortex and jet currents alter the magnitude and direction of wall shear stresses, forming stagnation rings near the shear stress direction transition region. (3) As the distance increases, the jet-affected region contracts, shock waves produce broader but shorter-lived pressure increases compared with the more localized, sustained pressure from the jet. These findings provide valuable insights into the complex interplay between cavitation bubbles and nonflat surfaces, enhancing the understanding of vortex dynamics and their mechanical effects.