Numerical analysis of fluid-material coupled method on propagation of pressure and stress waves during non-spherical bubble collapse

Abstract

When analyzing cavitation erosion, it is necessary to grasp the stress state inside a material due to the bubble collapse process. In this study, the behavior of a vapor bubble collapse and the stress distribution inside the material due to the bubble collapse were analyzed by using an in-house fluid/material coupled numerical method. In order to evaluate the stress inside the material, the “stress influence area” is introduced and used for the evaluation of the amount of input stress to the material. For analysis results, the two times of impulsive pressure occur in a first collapse, which is caused by two kinds of mechanism, one is a micro-jet, and the other is pressure waves of rebound of the toroidal bubble. Even though the impulsive pressure on a material surface by the micro-jet is smaller than the pressure waves of rebound, the maximum equivalent stress which is installed inside the material is nearly the same value. Further, even though the maximum equivalent stress generated in the material is almost the same, the "stress influence area" is overwhelmingly large in the case of the pressure waves of the rebound as compared to the micro-jet. Therefore, it indicates that the stress state inside the material cannot be predicted just by the measurement of impulsive pressure on the material surface.

Keywords

• bubble collapse
• erosion
• microjet
• pressure of rebound
• coupled analysis