When fluid pressure goes below the vapor pressure and phase change occurs, this phenomena is called ‘cavitation’. Cavitation can induce unfavorable effects such as noise or performance degradation, and erosion. However, fundamental study of cavitation is still scarce.
Calculating the pressure fields only allows us to speculate the possible region of cavitation, but not its specific generating spots. Furthermore, the effects of surface tension, viscosity, and cavitation nuclei introduced by impurities, is still unclear. Therefore, research implements ‘laser-induced cavitation’ to answer such questions.
Firstly, the beam is expanded about 10 times to obtain a larger beam diameter to provide wide convergence angle. Secondly, the expanded beam is converged by a plano-convex lens to focus the laser energy at the beam waist. By generating cavitation bubbles in exact spots (optically designed beam waist), we can systematically study the behavior of cavitation bubbles near a solid surface or inside a bulk fluid.