Small‐scale detonation experiments were conducted in a controlled atmosphere chamber to investigate the post‐detonation reactivity of a fuel‐rich, plastic bonded explosive. The atmosphere surrounding these 20 g explosive charges was varied in oxygen content from 0.2 to 100% with the total pressure held constant at 101 kPa. The performance of this small‐scale explosive charge is sensitive to the changing atmospheric conditions, perhaps more so than a larger charge size, due to burning inefficiencies corresponding to a scaling effect (increased surface area to volume ratio). Time‐resolved optical emission spectroscopy was used to contrast the dependence of the post‐detonation combustion properties on external oxygen content. The dominant near‐ultraviolet and visible emission features evolve from aluminum (Al) and aluminum monoxide (AlO) when oxygen is present. The time evolution of AlO emission was used to estimate the aluminum particle burning times, which lengthen from 6 to 31 μs as the oxygen content is reduced from 100 to 1%. The absence of AlO spectral features below 1% oxygen levels imply that the emission spectroscopy applied to this detonation environment is most sensitive to the aerobic component of the post‐detonation combustion. Pressure and optical pyrometry measurements recorded during the same experiments exhibit the strong dependence of the early time energy release on the oxygen content in the surrounding atmosphere. Numerical simulations of the detonation and subsequent multiphase flow expansion predict the position of the fuel particles to extend beyond the detonation products and, in some cases, beyond the shock front during the timescales covered in these experiments, stressing the importance of mixing with ambient oxygen for early combustion to occur.

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Multiphase flows are present in many important fields ranging from multiphase explosions to chemical processing. An important subset of multiphase flow applications involves dispersed materials, such as particles, droplets, and bubbles. This work presents an Eulerian–Eulerian model for multiphase flows containing dispersed particles surrounded by a continuous media such as air or water. Following a large body of multiphase literature, the driving force for particle acceleration is modeled as a direct function of both the continuous-phase pressure gradient and the gradient of intergranular stress existing within the particle phase. While the application of these two components of driving force is well accepted in much of the literature, other models exist in which the particle-phase pressure gradient itself drives particle motion. The multiphase model treats all phases as compressible and is derived to ensure adherence to the 2nd Law of Thermodynamics. The governing equations are presented and discussed, and a characteristic analysis shows the model to be hyperbolic, with a degeneracy in the case that the intergranular stress, which is modeled as a configuration pressure, is zero. Finally, results from a two sample problems involving shock-induced particle dispersion are presented. The results agree well with experimental measurements, providing initial confidence in the proposed model.

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