The formation, propagation and stability of self-sustained detonation waves in gaseous mixtures, condensed-phase explosives and media with hydraulic resistance

We examine the mechanism of the formation and propagation of fast deflagration waves in gaseous mixtures as a result of the breakdown of the one-dimensional detonation wave in a model of the three-step reaction. Based on the numerical simulations, we demonstrate that the failure of the detonation wave is due to the development of one-dimensional instabilities and propose a mechanism that explains the experimentally observed propagation of the fast deflagration wave.; The propagation and stability of detonations with an internal sonic point is considered and the effects of the front curvature is investigated. We consider two realistic examples of pathological detonations: a two-step reaction model with an endothermic second reac tion and a model one-step reaction with a mole decrement and an increase of the mixture specific heat capacity. In the limit of weak curvature, we construct the detonation speed versus curvature relation. Our numerical simulations of exploding and imploding cylindrical and spherical detonations show good agreement with quasi-steady predictions of the front trajectories.; A detonation initiation of an idealized condensed-phase explosive is studied in a framework of the pressure-sensitive reaction rate model. We consider initiation induced by the passage of a piston-driven shock and initiation induced by the evolution of non-uniform initial perturbations of the explosive material. We obtain the time of the initial explosion, the weak detonation path, and the point of the strong detonation emergence. For nonuniformity-induced initiation, we also present the analytical asymptotic solution, which describes the evolution of disturbances leading to the formation of the weak detonation wave and its potential transition to a strong detonation. This solution has good agreement with the exact numerical results and has a better predictive capability compared with the constant-volume approximation.; Finally, we consider the propagation of a detonation though media with hydraulic resistance. In the framework of the model three-step reaction we demonstrate multiplicity of the detonation regimes. We construct detonation speed versus friction curves for super-detonation, choking detonation, and shockless subsonic detonation. Numerical investigation of stability of subsonic detonation shows that an increase of hydraulic resistance destibilizes the detonation, wherease an increase of the chain-branching temperature has the opposite effect.