Multiphysics code validation and sensitivity analysis through integrated modelling of convergent shock tube experiments*

A fundamental requirement to have confidence in the predictive capabilities of multi-physics simulation methods is their ability to reproduce verification and validation data. This submission presents a sensitivity study performed using the convergent shock tube experiments of Setchell et al. [1]. Depending on the Mach number of the incident shock, the experiment demonstrates deviation from ideal gas and the onset of multi-level ionisation after successive overlapping of shocks on-axis following reflection from the inner walls, significantly impacting the subsequent dynamics. Despite substantially lower temperatures than typical ICF conditions, with the transition from a high-temperature gas to a plasma the experiment provides important validation data for codes modelling coupled physical phenomena.

In addition to a substantial sensitivity to the equation of state, attributed to discrepancies in when materials undergo ionisation, a principle sensitivity is found in the modelling of thermal conduction across material interfaces. This work therefore offers crucial insight into uncertainties in modelling heat flow, as discussed in our recent work [2].

[1] R. E. Setchell et al., J. Fluid Mech, 56, 3, pp. 505-522 (1972)

[2] D. A. Chapman et al., Phys. Plasmas 28, 072702 (2021)