Ab initio simulation of gaseous mixture flow through an orifice

A flow of mixture of rarefied gases through a thin orifice is calculated applying the direct simulation Monte Carlo method based on ab initio (AI) potential. The calculations have been carried out over a wide range of the gas rarefaction, for three values of the pressure ratio, and for five values of molar fraction with the numerical error of the flow rates less than 0.5%. A comparative analysis showed that the flow rate of mixture has a behavior qualitatively different from that for a single gas. To check the accuracy of the hard sphere (HS) molecular model, additional simulations were carried out based on this model. It is found that the relative difference of the flow rate based on the AI potential from that obtained for the HS molecular model depends on many factors, namely, chemical composition, pressure ratio, and gas rarefaction. The discrepancy of the flow rates based on the two potentials reaches 3%. A comparison of the axial distributions of density, temperature and bulk velocity shows that the Mach disc for the mixture considered here is weaker than that for single gas. Two-dimensional fields of density, temperature and local Mach number are presented for some values of the pressure ratio.