High-enthalpy flow over a rearward-facing step – a computational study

Hypersonic, high-enthalpy flow over a rearward-facing step has been numerically investigated using computational fluid dynamics (CFD). Two conditions relevant to suborbital and superorbital flow with total specific enthalpies of $26$ and $50~\mathrm{MJ} ~{\mathrm{kg} }^{\ensuremath{-} 1} $, are considered. The Mach number and unit Reynolds number per metre were 7.6, 11.0 and $1. 82\ensuremath{\times} 1{0}^{6} $, $6. 23\ensuremath{\times} 1{0}^{5} $ respectively. The Reynolds number based on the step height was correspondingly $3. 64\ensuremath{\times} 1{0}^{3} $ and $12. 5\ensuremath{\times} 1{0}^{2} $. The computations were carried out assuming the flow to be laminar throughout and the real gas effects such as thermal and chemical non-equilibrium are studied using Park’s two-temperature model with finite-rate chemistry and Gupta’s finite-rate chemistry models. In the close vicinity of the step, detailed quantification of flow features is emphasised. In particular, the presence of the Goldstein singularity at the lip and separation on the face of the step have been elucidated. Within the separated region and downstream of reattachment, the influence of real gas effects has been identified and shown to be negligible. The numerical results are compared with the available experimental data of surface heat flux downstream of the step and reasonable agreement is shown up to 30 step heights downstream.