Experimental and numerical study of the dynamics of a laser-induced cavitation bubble between two parallel walls: Effect of confinement and viscosity

The collapse of a cavitation bubble near a rigid boundary induces a high-speed transient liquid jet that accelerates the liquid to the boundary. In this study, the dynamics of a laser-induced bubble confined between two parallel walls is studied experimentally and numerically. The effects of confinement/gap distance H as well as the off-centre distance δ on the dynamics of the bubble are examined. The numerical results are validated against the corresponding experimental data in terms of the evolution of the bubble shape during expansion, collapse, and rebound. Furthermore, a case with a more confined situation is considered. The numerical simulation elucidates intricate aspects of the bubble dynamics around the jet impact, which are not obtainable through experiments. The numerical results are scrutinised in a more comprehensive manner in order to derive the pressure and velocity fields, thereby determining their impact on the walls. It was found that the location of the bubble with respect to the walls and the degree of confinement determine the number as well as the strength of the liquid jet. Typically, when the confinement increased (H decreased), the peak pressure at the upper wall decreased significantly (17%) for a given off-centre distance δ, whereas at the lower wall, it decreased by 39%. Furthermore, the velocity at the upper and lower walls decreased by approximately 2% and 20%, respectively. Finally, the liquid jet’s pressure and velocity impacting on the rigid walls decrease with increasing the liquid viscosity. This study provides new insights into the complex fluid dynamics of confined laser-induced cavitation bubbles, which is relevant for various engineering applications.