Detonation Initiation: Modelling, Computation and Mechanisms

Mechanisms underlying detonation initiation in 1-D and 2-D configurations are explored computationally. The strong state-sensitivity of the underlying chemical kinetics causes the reaction zones to be exceedingly thin, and accuracy of solution demands that the computational scheme provide the necessary resolution with economy. This is achieved by a technique that employs overlapping grids and block-structured adaptive mesh refinement. We consider flows described by the reactive Euler equations with an ideal equation of state and various stiff reaction models. These equations are solved using a second-order accurate Godunov method for the convective fluxes and a Runge-Kutta time-stepping scheme for the source term modelling the chemical reactions. Numerical results are presented for evolution to detonation in a slab and in an annulus, provoked by an initial temperature gradient. Results are also presented for the extinction and rebirth of an overdriven detonation in an expanding channel.