Aerothermochemical effects on vorticity generation at a curved shock and post-shock evolution

Numerical simulations of a two-dimensional high-enthalpy hypersonic flow over wedge geometries were performed to examine the effects of aerothermochemistry on vorticity generation at a curved shock and in its post-shock region. Three wedge angles ( 0 Superscript ring 0 ∘ $0^\circ$ , 20 Superscript ring 20 ∘ $20^\circ$ and 40 Superscript ring 40 ∘ $40^\circ$ ) and four nitrogen–oxygen mass fraction combinations, ranging from pure normal upper N 2 N 2 $\mathrm{N_2}$ to pure normal upper O 2 O 2 $\mathrm{O_2}$ , were considered, alongside a calorically perfect gas case for comparison. The numerical predictions were compared with 10 Superscript ring 10 ∘ $10^\circ$ wedge experiments, capturing the observed trends in shock stand-off distance associated with variations in oxygen fraction. It was found that endothermic dissociation lowers post-shock temperatures near the stagnation point, increasing density. This reduces the stand-off distance of the leading bow shock, enhancing its curvature and, hence, the vorticity generated. Away from the stagnation point, temperature-dependent specific heat produces local inflections at the transition from the bow shock to an oblique shock for the largest wedge angle, generating vorticity opposite to that induced by the bow shock. In the post-shock region, expansion along the body stretches vorticity, reducing its magnitude over the flat region, with smaller wedge angles amplifying this effect. Dissociation increases formation enthalpy (associated with chemical composition) while reducing sensible enthalpy (associated with temperature) and kinetic energy under total enthalpy conservation. Fluid passing near the stagnation point undergoes the strongest dissociation, leading to steep velocity gradients and enhanced near-wall vorticity even under slip-wall conditions. Finally, the vorticity immediately downstream of the shock closely follows classical relations based on free-stream conditions and shock geometry, demonstrating strong agreement between the numerical results and the theoretical predictions.