Computational challenges for simulations related to the NASA electric arc shock tube (EAST) experiments

The goal of this study is to gain some physical insights and an understanding of the computational challenges for the simulations related to the hypersonic nonequilibrium multi-species and multi-reaction experiments on the NASA Electric Arc Shock Tube (EAST). While experimental measurement does not provide any information about the radial structure of this type of flow, accurate and reliable numerical simulations can provide more insight into the physical structure of the flow to aid the design of atmospheric entry spacecrafts. The paper focuses on the spurious numerics which take place in numerical simulations of the subject physics containing stiff source terms and discontinuities. This paper is based on the knowledge gained from Yee et al. on simple reacting test cases(Yee et al. 2013, [9]) as a guide to reveal the computational challenges involved for such an extreme flow type. The results of the 1D and 2D EAST viscous and inviscid simulations using a simplified physical model are presented. The computation reveals, for the first time, that the 2D viscous model which contains both shocks and shears exhibits Tollmien-Schlichting-like instability complex patterns at the boundary layer. In addition to exhibiting spurious numerical behavior of wrong propagation speed of discontinuities by typical shock-capturing methods, there is improved understanding on the cause of numerical difficulties by previous investigators. One example is that the relative distance between the shocks and shear/contact is different from one grid spacing to another for each considered high order shock-capturing scheme. The results presented can provide insight on the numerical instability observed by previous investigations and future algorithm development for this type of extreme flow. Published by Elsevier Inc.