Effects of cylinder-wall distance on re-shock interaction with fuel cylinders at near-critical thermodynamic states

In high-speed propulsion systems, for instance, scramjets and ramjets, shock waves impacting the fuel-environment gas interfaces at near-critical thermodynamic states is a phenomenon that is frequently encountered. The effects of shock waves on fuel cylinders with the inclusion of real-fluid features remains a relatively underexplored area of research. In this study, we investigate the influence of re-shock on the shocked fuel cylinder at near-critical thermodynamic states. The spacing between the fuel cylinder and the wall is varied from 1.5R to 9R. The simulation employs compressible multi-component equations and real-fluid thermodynamic relationships to model the evolution of the cylinder and the dynamics of the surrounding gas flow. A hybrid numerical scheme based on finite volume is used to capture shocks and interfaces. The approach has been validated against reference data and shows excellent agreement. The effects of varying cylinder-wall distances on the evolution of the surface of the re-shocked fuel cylinder are thoroughly analyzed. The analysis presented covers intricate shock and re-shock impingement, cylinder deformation, cylinder displacements, and vortex development. A range of features at different stages of evolution are analyzed quantitatively and qualitatively. These include wave pattern evolution, pressure redistribution, shift properties (center-of-mass parameters), cylinder geometry deformation characteristics (cylinder width), baroclinic vorticity distribution, circulation histories, and enstrophy progression. The analysis also quantifies changes over time in the characteristic mixing degree between the fuel and ambient gas. Two additional parameters, the area and the mass fraction-weighted area of the mixing region, are included. Current studies could provide valuable insights for experimental design and industrial applications involving gas-fuel mixing processes at near-critical thermodynamic states.