Numerical Analysis of Nonspherical Bubble Collapse Behavior and Induced Impulsive Pressure during First and Second Collapses near the Wall Boundary

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Cavitation often involves an abrupt phase change phenomenon. This phenomenon causes cavitation erosion on the material surface. In particular, violent bubble collapse near the material surface causes severe erosion. Numerical simulation is a powerful approach by which to clarify the high-speed, complex bubble collapse behavior near the wall boundary. In the present study, numerical analysis of nonspherical bubble collapse behavior and induced impulsive pressure at several initial standoff distance from the wall boundary is performed using a locally homogeneous model of a gas-liquid two-phase medium. The second collapse is confirmed to be more violent than the first collapse, and a circular erosion pattern is predicted owing to a toroidal bubble collapse attached to the wall boundary at a certain standoff distance. The influence of the symmetry breaking of the initial spherical bubble shape on the collapse behavior is investigated, and the asymmetry is found to influence the second bubble collapse, especially the generation of the high impulsive pressure in the central area.
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