Numerical Investigation on Influence of Number of Bubbles on Laser-Induced Microjet

In this study, the impact of the number of bubbles on the velocity of laser-induced microjet is numerically investigated, focusing on the pressure wave propagation generated by multiple laser-induced bubbles. First, we show that the microjet velocity increases with the increasing impulse of the pressure wave propagating to the meniscus direction. This result indicates that it is possible to study the structure of the pressure field generated from bubbles to investigate the effect on microjet generation. In addition, it is found that the microjet is weakened with the increase in the number of bubbles. Next, we show that the propagation of the pressure waves has two types. The first type is propagating from a bubble to a meniscus. The second type is propagating round trip between nearby bubbles or by the bubble itself. Finally, we explain the reason for the decrease in the microjet velocity with the increasing number of bubbles by an expansion history of the bubbles, which depends on their interaction with the pressure waves. These results could help to design not only laser-induced microjet generation but also devices that use laser-induced bubbles generated in a microchannel.