Modeling of afterburning from the particle hydrodynamics of explosive product interface motion

Abstract

The detonation of metalized high explosives (HE) generates a complex multiphase flow field. The detailed modeling of this process requires knowledge of the metal particle reaction rate and properties of the mixing layers. Two-dimensional compressible flow model is used to describe radial distribution of the HE product dispersal. The explosive radial expansion of HE products is strongly characterized by developing instabilities at the contact interface (CI) between the HE products and the air. The instability is influenced by various mechanisms which include classical Rayleigh-Taylor (RT) and Richtmyer - Meshkov (RM) effects. For the given radial distribution of HE products, the simplified afterburning model is applied. Three cases considered are: (1) instantaneous release of the explosion energy requiring no afterburning; (2) delayed energy release involving 50% of the energy associated with afterburning process which is distributed uniformly and steadily within the fireball; (3) energy release confined within the mixing zone only. We show that the peak pressure for the first shock decreases while it increases for the second shock when afterburning is included. The total energy release over a longer time in general increases the peak value of the impulse, which is defined as the area under the pressure-time curve, at a given distance. The afterburning reduces the rate of decay of the shock pressure, increases the local gas temperature, and hence increases the velocity of the secondary shock front. The amplification of the impulse and the secondary shock peak pressure is higher when the afterburning energy is released within the mixing layer rather than uniformly across the fireball radius.