Opposing steady and transiently developing jets in relation to laser machining

The opposing jet situation in relation to laser gas assisted drilling process is considered. In this case, impinging steady jet resembling the assisting gas jet and transiently developing jet resembling the vapour jet emanating from the solid surface due to laser ablation are employed in the analysis. A numerical method using a control volume approach is introduced for simulating the flow and temperature fields. Since the thermophysical. properties of the transiently developing vapour jet are not known, helium jet at 1500 K is accommodated in the simulations. Helium is a chemically stable inert gas, which does not ionize at 1500 K. The inlet conditions of transiently developing jet are taken from the previous study. It is found that the enhancement of the radial flow, due to opposing situation, generates a circulation cell next to the steady jet boundary. The orientation and size of the circulation cell changes with time thereby modifying the streamline curvature of the steady jet. The transiently developing jet does not behave like a transiently self-developing one. Moreover, the radial jet resulted from the opposing jets behaves almost like a free jet.