Cavitation characteristics of water guided laser nozzle on water jet fiber stability

The generation of a stable and reliable water jet fiber is essential for optimizing the performance of water-guided laser systems, as cavitation significantly impacts its stability. This study utilizes computational fluid dynamics to simulate various nozzle structures and analyze the effect of cavitation on water jet fiber stability. Numerical simulations were conducted to examine the behavior of downward conical nozzles both with and without cavitation effects. The research aims to explicate the mechanisms governing cavitation formation and its impact on jet stability. Additionally, this study investigates how nozzle structural parameters, including the length-to-diameter ratio, divergence angle, and orifice diameter, affect jet stability under cavitation conditions. A multi-objective genetic algorithm is subsequently employed to globally optimize the Kriging surrogate model, thereby facilitating the identification of Pareto-optimal solutions for enhancing the stability characteristics of the water jet fiber. High-speed camera visualization was utilized to systematically investigate the stability and fragmentation mechanisms of the water jet. Experiments conducted using a 532 nm green laser source confirmed that the optimized downward conical nozzle can produce a stable water jet fiber. Specifically, an optimized nozzle with a 0.08 mm aperture can generate a stable water jet fiber extending up to 84 mm in length under an inlet pressure of 5.0 MPa, thus meeting the requirements for efficient water-laser coupling. This study provides valuable insights and guidance for enhancing water-guided laser processing technology and its practical engineering applications.