激光诱导水动力学和气泡的PIV和PDA实验研究

Research on laser-liquid interaction and its induced fluid flows, as well as microbubbles, is important in many applications, such as laser ophthalmic microsurgery, manufacturing and repairing of micro-electronic-mechanical devices, laser deposition of thin liquid film to a specific location in micro system, etc. This work was focused on the interaction mechanisms of a laser pulse with distilled/degassed water as well as the characteristics of the microbubbles. Microbubbles and optohydrodynamic flows induced by a Nd:YAG pulse laser (New Wave Research) were studied. A recently improved PIV and PDA system were used to analyze the bubble dynamics and fluid flow quantitatively. Two CCD cameras were used to capture the images of microbubbles and visualize the laser induced Optohydrodynamic flows. The experimental results show that a bright fluid beam (density flow) with duration less than 127μs is produced by a focused laser pulse while an explosive cavitation just around the focus point is also occurred. Immediately following the fluid beam and the explosive cavitation, two new fluid regions which may be formed with the superheated dense fluid were found. One of them is just under the fluid beam due to the optical pressure while the other one is around the explosion area due to the force caused by the explosive cavitation. As shown in Figure 1, Single and multi microbubbles were generated immediately after the cavitation explosion when the nucleation conditions were satisfied. In addition, the characteristics, such as bubble velocities and diameters, were measured by a recently improved phase-Doppler anemometry (PDA). These results will help to have a better understanding of the mechanisms of laser-induced optohydrodynamic flows and bubbles related phenomena, which is crucial to numerical modeling.