Influence of quantum intermolecular interaction on internal flows of rarefied gases

In order to model gaseous flows over the whole temperature range beginning from 1 K, the intermolecular interaction should be considered on the basis of quantum approach. Such a consideration becomes important in case of light gases like helium and hydrogen. Recently, the direct simulation Monte Carlo (DSMC) method widely used to calculate flows of gases has been generalized to implement the quantum approach to intermolecular collisions. To evaluate the influence of the quantum scattering on typical flows of light gases, a benchmark problem has been solved for two helium isotopes 3He and 4He using an ab initio potential. More specifically, the flow-rate and flow-field of helium flowing through an orifice have been calculated over the temperature range from 1 K to 300 K for various values of the pressure ratio with the numerical error of 0.5%. As expected, no influence of the quantum effects on the flow-rate has been detected for the temperature 300 K. Though, the quantum approach requires less computational effort than the classical one at this temperature. For temperatures lower than 300 K, the influence of the quantum effects exceed the numerical error and reaches 41% at the temperature of 3 K. In this case, the quantum interaction is the only approach to model gas flows.