In one space dimension ZND detonations are either stable or unstable to some perturbation. The result of the perturbations, if the detonation is unstable, is a pulsating mode instability. The following figures illustrates this behaviour for several unstable detonations. The degree of instablity is controlled by decreasing the speed of propagation of the wave. The lower the speed of propagation, for a given heat release and activation energy, the more unstable the detonation becomes.
The figures were obtained with an activation energy of 50 and a heat release of 50 and a ratio of specific heats of 1.20. The mesh resolution was 50 cells per half reaction length (of the steady ZND wave) for the first three computations and 200 for the last three. Each figure shows the pressure ratio at the perturbed shock front of the detonation.
f=1.70, 1.60, 1.50
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