A Single Cavitation Bubble Induced Damage

Abstract

In the present work, we experimentally and numerically investigated the dynamics of a millimeter-sized cavitation bubble generated nearby a solid surface. In experiments, bubbles are induced by a focused Nd-YAG laser generating plasma. A specimen of the commercially pure aluminum surface was placed nearby a bubble at varying relative wall distances. Here, the relative wall distance is a ratio of the distance between the bubble center and specimen surface, and the maximum radius of the bubble. In experiments, we captured the bubble’s dynamics by back illumination method using a highspeed camera. Damage obtained was characterized by an optical microscope and profilometer. The surface profiles and damage patterns quantified the damage characteristics. The three-dimensional flow was captured numerically by solving the Navier-Stokes equations in an Euler-Euler approach with barotropic equations of state. The computations were performed assuming both water and vapor as compressible phases. The dynamics of a single bubble obtained in computations were compared with the experiments for shapes and collapsing times. The computed characteristics of flow around a bubble near the solid surface, e.g. impact velocities and pressures were also discussed. Additionally, the dynamics of a microscopic bubble collapse near the surface was also investigated to compute collapse-induced wall shear rate and flow around the collapsing bubble. The results of numerical simulations were compared with the existing experimental data. The comparisons showed, a good qualitative and quantitative agreement. Overall, the numerical method well reflected the dynamics bubble up to three collapses and resolved flow around the bubble. The statistical data of pits obtained are also useful in deriving loads induced by a single bubble collapse. Overall, this work extensively comprises the single cavitation bubble dynamics and induced damage. This article summarizes the investigations of Sagar (2018) and Sagar & el Moctar (2020).