Molecular Dynamics Simulations of Shock Waves in Mixtures of Noble Gases

We study the structure of a normal shock wave in noble gas mixtures (Xe-He and Ar-He) of various compositions using molecular dynamics and direct simulation Monte Carlo. The molecular dynamics simulations are first validated against experimental data. Good agreement is found between the molecular dynamics solutions and the experimental measurements, with the exception of the parallel temperature profile in the 24.7% Ar-He mixture, despite the satisfactory agreement between the parallel velocity profiles. Secondly, a validation against direct simulation Monte Carlo solutions obtained with the accurate generalized hard sphere model is presented. As expected, the generalized hard sphere direct simulation Monte Carlo and molecular dynamics solutions are in near-perfect agreement. Finally, molecular dynamics results are compared to those obtained with the lower fidelity variable hard sphere model, which, if inappropriately parametrized, fails to describe the shock wave structure. This work exemplifies how full molecular dynamics solutions could be used to precisely discern differences between phenomenological models of various accuracy.