The time-dependent reaction zones of nitromethane and liquid TNT have been investigated using one-dimensional numerical hydrodynamics with Arrhenius chemical reaction and accurate equations of state. The formation of an overdriven stable detonation in nitromethane by various types of pistons has been investigated. A piston whose velocity decreases abruptly to a lower value produces an initially short reaction zone which lengthens and decreases in pressure, when the second and lower velocity occurs, until the rate of release of chemical energy exceeds that necessary to sustain the wave. If the stepped-velocity piston has a sufficiently small lower step, failure of the detonation occurs in the time and space scale of interest. If the detonation is not sufficiently overdriven, the solution of the equations is nonsteady and periodic, oscillating about the steady-state (time-independent) solution.
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