The stability of 30-μm-diameter water jet for jet-guided laser machining

Abstract

Combined water-jet process and laser machining, the water jet-guided laser processing is suitable in processing a thin and sensitive material with a high degree of precision required. Given that there are many uncertainties of the jet with lower than a 50-μm-diameter nozzle and lower velocities in the stability field of water jet-guided laser machining, a numerical model of a 30-μm water jet, considering the number of grids and the influence of meshes, has been studied to meet the requirements of micrometer order precision machining. Furthermore, the critical Reynolds number and the critical jet exit velocity of the case with a 30-μm-diameter nozzle have been presented to make a comparison between turbulence flow and laminar flow in air with different jet exit velocities from 0.2 to 500 m/s. Hence, the optimal jet exit velocity to achieve the longest stable length of water jet was found. Besides, three cases of 15 m/s jet exit velocity are simulated in different degrees of vacuum, which suggest water jets in vacuum are much more stable than those in atmospheric environment. Finally, a conjecture about water-jet simulation with a smaller diameter of nozzle is proposed as a future work.