Combined Molecular Dynamics Simulations and Regression Analysis for High-Speed Reacting Flows*

The accurate simulation and diagnosis of high-speed reacting flows are essential for advancing the design and analysis of chemically fuelled propulsion and energy systems. A major challenge lies in modelling the rapid interactions of strong shocks waves and chemical reactions in these flows. Understanding the effect of non-equilibrium and subcontinuum scale dynamics is essential for accurate modelling. To this end, we perform combined molecular dynamics (MD) simulation and data analysis of shock propagation in reacting and non-reacting H₂/O₂ mixtures with a pressure ratio of O(10). The complex interatomic interactions with active chemical bonding and collisions complicates the identification of coherent dynamics of molecules from the simulation. By newly applying regression analysis to the time series data of molecules moving across shock waves, we extract both continuum and subcontinuum scale dynamics and translate the information into macroscopic descriptions . Results are then compared with continuum direct numerical simulations of the compressible multi-component Navier-Stokes equations. The continuum-scale quantities of the MD simulations, including post-shock velocities, are validated. Lastly, the coherent dynamics of molecules within the shock region is analysed and discussed.