Numerical Investigation of Shear Instability, Mixing and Afterburn Behind Explosive Blast Waves

Abstract

A hybrid two-phase numerical methodology is used to study the propagation of explosive blast wave from spherical charges of TNT and their interaction with ambient distribution of aluminum particles. The presence of these particles is found to cause Rayleigh-Taylor instabilities at the contact surface between the detonation products and the shock-compressed air, which results in enhanced mixing and afterburn. The afterburn energy release is not observed to aect the primary blast wave, but aects the pressure decay rate behind the blast wave, and the speed and the strength of the secondary shock. The dispersion and reaction of aluminum particles in the hot region behind the blast wave is investigated for a range of particle sizes and mass loading, and the role played by these particles in the growth of hydrodynamic instabilities is studied. It is shown that for the range of sizes investigated, particle size does not play a signican t role in the mixing, but the distribution and initial extent do have appreciable impact. It is found that large particles do not ignite, while small particles rapidly ignite and burn completely. Furthermore, intermediate size particles are observed to ignite only when the mixing is enhanced, however, subsequently quench as they leave the mixing layer. This study has provided some useful insights on the instabilities induced by ambient reactive particles in detonation o w-elds and establishes a simulation capability to study turbulent two-phase processes in an explosive environment.