Comparison between continuum and molecular dynamics simulations in shock-to-detonation transition

This study investigates the intricate relationship between shock waves and chemical kinetics, specifically focusing on the role of translational non-equilibrium in shock-induced chemistry during the shock to detonation transition in a reactive gas. Molecular dynamics simulations are employed and compared with continuum descriptions using reactive Euler and Navier–Stokes models for hard spheres. Results reveal a significant impact of translational non-equilibrium on shock amplification rates and the transition to detonation, with an approximately twofold acceleration compared to conventional Euler hydrodynamic models. Notably, a Navier–Stokes model incorporating hard sphere transport properties effectively captures this acceleration, emphasizing its implications for modeling gaseous detonations with finite-rate, collision-controlled chemistry (i.e., reactions whose characteristic time is comparable to the translational relaxation time) and complex pressure wave dynamics. The study concludes that non-equilibrium effects, particularly those associated with molecular hotspots, may lead to corrections in reaction rates and shock dynamics, underscoring the importance of considering diffusive effects for accurate modeling of gaseous detonations.