Modelling the laser fusion cutting process: II. Distribution of supersonic gas flow field inside the cut kerf

A mathematical model is developed to calculate the distribution of the gas flow field at the entrance, inside and exit of a laser cut kerf for inlet stagnation pressures ≥5 bar for an inert assist gas jet exiting from a supersonic nozzle. A two-dimensional analytical method is adopted to locate approximately the position and shape of the detached shock above the cutting front surface according to the geometrical shape of the cutting front. A method of two-dimensional characteristics is applied to calculate the gas flow field distribution along the cutting front. The calculated results of the flow field distribution are simulated by the computer and can be used to estimate and analyse the cut-edge quality under different cutting conditions.