• A rigorous two-stage DNS framework is developed to provide high-quality reference data for shock-turbulence-flame interactions in supersonic reacting shear layers using a moderately complex hydrocarbon fuel. • The flow is shown to be remarkably robust to variations in mean scalar dissipation rate, with reaction rates governed by localized regions of high scalar dissipation, implying accurate modelling is possible at lower grid resolutions than traditionally expected. This study examines critical aspects of Direct Numerical Simulations (DNS) of ethylene-air combustion for hypersonic propulsion applications. A combustion mechanism was selected based on a comparative analysis of multiple models, balancing chemical fidelity and computational cost. Detailed configurations of two DNS cases are presented, focusing on high-speed reacting turbulent shear layers including interactions with an oblique shock wave ( M s = 1.3 , inflow angle 5 ∘ ). A lower and standard Reynolds number case are employed to ensure mesh convergence while maintaining computational feasibility. Although most statistical quantities exhibit strong convergence trends, full convergence was not achieved for the scalar dissipation rate. This study investigates the underlying physical mechanisms responsible for this behaviour and demonstrates their limited impact on all other key variables. These results advance the understanding of turbulence-combustion interactions and will be used to guide new developments in numerical modelling for next-generation air-breathing hypersonic propulsion systems.
Cai et al. (2026) studied this question.