Numerical simulation of the influence of tube diameter on detonation regime and structure in mixtures with two-step energy release and double cellular structure

We present the results of a numerical study of the detonation structure in a reactive mixture whose chemical energy is released in two steps of very different characteristic times. Detonation in these mixtures exhibits a double detonation cellular structure. By decreasing the detonation tube diameter, several detonation structures are successively obtained: a multiheaded double cellular structure, a double cellular structure with a spinning mode of the transverse wave of the second exothermic step, a single cellular structure, and a spinning mode of the transverse wave of the first step. This is the first three-dimensional numerical investigation of such mixtures. Although a lack of resolution does not allow a resolution of the fine structure at the beginning of the large detonation cells, the results agree qualitatively with experiments.