Abstract:

Multiphase explosions and post-detonation flows have been significant hazards for centuries, plaguing humankind ever since we have been storing small grains. Despite their long history of study and application to engineering and the mili-tary, multiphase explosions remain poorly understood. They are highly transient and involve nonlinear coupling between many different physical processes across a wide range of length and time scales. In particular, the interactions between shock waves, particle dispersal and burning, turbulence, and afterburning fuel-rich fireball gases have been longstand-ing questions in post-detonation flows. This presentation discusses a simulation effort aimed at understanding post-detonation multiphase flows and the development of numerical algorithms that enable them. The governing equations are described by a three-phase approach that couples explosive detonation, a compressible reactive gas with detailed chemistry, and an Eulerian kinetic-theory granular flow model. Surprising results indicate that the afterburning of turbu-lent post-detonation fireballs transitions from a finite-rate chemistry regime at laboratory scales to a mixing-limited re-gime for larger explosive charges. Results for explosively-dispersed aluminum particles show a rich variety of ignition and combustion mechanisms that qualitatively explain experimental observations. The presentation will close with a brief dis-cussion of our latest efforts to simulate the effect of polydisperse size distributions on the combustion dynamics of explo-sively-dispersed reactive particles.