INDUCED BREAKDOWN SPECTROSCOPY; CAVITATION BUBBLE; NANOPARTICLES; SIMULATION; UNDERWATER; COLLAPSE; LIQUID; VALIDATION; TRACKING; GROWTH

Laser ablation of a solid target immersed in liquid (such as water) has many important applications such as laser synthesis of nanoparticles, lasermicromachining in water, and laser shock peening. Laser ablation of a solid target in water involves complicated physical processes. One important process often involved is the generation and evolution of a bubble in water and attached to the target surface, which may have significant effects on the target and the ambient water, and hence may greatly affect the relevant practical applications. Some experimental studies were reported in the literature on bubble evolutions induced by laser ablation of a solid target in water. However, the reported previous relevant physics-based modeling work is not sufficient. A physics-based model may help improve the process fundamental understanding and generate valuable information to related applications. In this paper, physics-based modeling work has been performed on the shrinking process of a bubble induced by laser metal ablation in water, together with time-resolved shadowgraph imaging experiments to verify the model. The model-predicted bubble evolution agrees reasonably well with the experimental measurement shown in the paper. Under the studied conditions, it has been found that near the bubble collapse moment (i.e., the moment when the bubble shrinks to a minimum size): (1) the bubble shrinks very fast, and the peak fluid velocity magnitude occurs inside the bubble and can exceed similar to 550 m/s; (2) the temperature inside the bubble increases very quickly and approaches similar to 2000 K; and (3) the pressure inside the bubble becomes very high, and can reach a peak magnitude of similar to 380 MPa at the collapse moment at the bubble center. During the shrinking process, a high-pressure region outside and near the bubble wall is generated near the collapse moment, but the temperature of the region outside the bubble mostly remains low. Published by AIP Publishing.