Supersonically expanding stationary thermal
plasma, formed by a thermal cascaded arc is
studied. Due to the low chamber pressure (20-100 Pa) the results of
continuum mechanics model can be doubtful. This is why these results are
validated against kinetic Monte Carlo simulation and experimental data
obtained by means of laser induced fluorescence. The analysis proves that
continuum mechanics is still applicable for the velocity and temperature
field predictions downstream of the shock region. However, the shock
formation and some non-equilibrium effects typical for supersonic flow can
be correctly studied only with the help of kinetic simulations. We show that
the errors in the results using continuum mechanics can be attributed to the
presence of flow gradients. These errors diminish when the shock regions are
thickened due to rarefaction, viscosity and heat conductivity. Besides, both
methods show that the effect of the chamber geometry on the plasma flow
field is important.