Influence of the gas-surface interaction model on time-dependent rarefied gas simulations

• Influence of the gas-surface interaction on time-dependent rarefied gas flow has to be considered in practical applications.
• It is argued that the domain of possible solutions is bounded by the cases of specular and diffuse scattering.
• It is demonstrated how the solution domain can be affected by measurement uncertainties present in the experimental setup.
• The obtained results are used to show the influence of the accommodation coefficient value on the gas separation mechanism.

In this paper, the influence of the gas-surface interaction on the time-dependent rarefied gas flow through a short tube into vacuum is investigated. Due to a significant scale separation, the flow is simulated using a hybrid scheme proposed by Vargas et al. [1, 2], in which the pressure change in the upstream chamber is coupled to the flow rate obtained by the Direct Simulation Monte Carlo (DSMC) computations. First, the influence of gas-surface interaction is demonstrated through comparison of DSMC simulation results obtained for different values of accommodation coefficients. The obtained dataset is then used to show how the boundary conditions can affect the time-dependent gas flow, even when applied on the small surface area of the device. It is argued that the domain of possible solutions is bounded by the cases of specular and diffuse scattering. Furthermore, it is investigated how this domain can be affected by measurement uncertainties present in the experimental setup. Next, the analysis of the gas-surface interaction is extended to binary mixtures. In the end, it is discussed how the obtained results can be used in order to improve the efficiency of gas separation mechanisms.