Comparison of the numerical solutions of the full Boltzmann and S-model kinetic equations for gas flow through a slit

The pressure-driven flow of a rarefied gas through a two-dimensional slit is analyzed on the basis of the full Boltzmann equation and its kinetic S-model applying the discrete velocity method. The calculations are carried out for the gas rarefaction ranging from the free-molecular to the hydrodynamic regime and for the reservoir pressure ratios leading to the subsonic or supersonic flow behind a slit. The structure of the flow field, given by both numerical approaches, as a function of the pressure ratio and the rarefaction parameter is examined. The mass flow rate and the distributions of density, bulk velocity and temperature along the symmetry axis are reported. An applicability of the S-model kinetic equation via comparison with the Boltzmann equation is discussed.