Modeling of the compressible vapor flow induced in a keyhole during laser welding

The compressible vapor flow inducing a keyhole in the deep penetration laser welding process is studied. Suitable boundary conditions are deduced by the mean of a ray-tracing procedure, and the finite volume method is used to solve the hydrodynamic equations governing the vapor flow. A steady-state solution gives the distribution of the vapor parameters, consisting of the density, the pressure, the temperature, the velocity, and the Mach number. The influence of the ambient pressure on the vapor flow is mainly investigated, and the occurrence of friction phenomena between the vapor and the keyhole walls resulting in a more uniform distribution of the pressure is observed. We note that the stabilizing effect of frictions is important at low ambient pressures.