Characterization of the Mixing Layer Resulting from the Detonation of Heterogeneous Explosive Charges

Abstract

A dense, two-phase numerical methodology is used to study the mixing layer developing behind the detonation of a heterogeneous explosive charge, i.e., a charge comprising of a high explosive with metal particles. The filtered NavierStokes equations are solved in addition to a sub-grid kinetic energy equation, along with a recently developed Eulerian-Lagrangian formulation to handle dense flowfields. The mixing layer resulting from the post-detonation phase of the explosion of a nitromethane charge consisting of inert steel particles is of interest in this study. Significant mixing and turbulence effects are observed in the mixing layer, and the rms of the radial velocity component is found to be about 25% higher than that of the azimuthal and zenith velocity components due to the flow being primarily radial. The mean concentration profiles are self-similar in shape at different times, based on a scaling procedure used in the past for a homogeneous explosive charge. The peak rms of concentration profiles are 23-30% in intensity and decrease in magnitude with time. The behavior of concentration gradients in the mixing layer is investigated, and stretching along the radial direction is observed to decrease the concentration gradients along the azimuth and zenith directions faster than the radial direction. The mixing and turbulence effects in the mixing layer subsequent to the detonation of the heterogeneous explosive charge are superior to that of a homogeneous explosive charge containing the same amount of the high explosive, exemplifying the role played by the particles in perturbing the flow-field. The nonlinear growth of the mixing layer width starts early for the heterogeneous explosive charge, and the rate is reduced during the implosion phase in comparison with the homogeneous charge. The turbulence intensities in the mixing layer for the

Numerical simulation of particle jet formation induced by shock wave acceleration in a Hele-Shaw cell

“…Shock-wave mitigation systems in storage facilities for explosives, or other locations where explosions may occur, can utilize dust suspensions or geometrical configurations of obstacles to reduce safety distances (Igra et al, 1987;Suzuki et al, 2000;. Metallic particles can be utilized in heterogeneous explosives to enhance blast properties (Balakrishnan and Menon, 2011), and such methods have been suggested for neutralization of bacterial spores (Henderson et al, 2015). Additionally, the bacterial spores themselves interact non-trivially with the shock wave (Gottiparthi et al, 2014).…”

“…Explosion-driven Rayleigh-Taylor instability in gasparticle mixtures. Physics ofFluids, 26(4):043303 Balakrishnan, K. and Menon, S. (2011)…”

Factors Influencing Temperature Fields during Combustion Reactions

“…The particulate additives introduced into the explosive charges may participate in the combustion reaction [1][2][3][4][5] or remain unreactive [6,7]. Upon ignition heterogeneous explosives give rise to an outward moving blast wave that attenuates due to the effects of spreading; simultaneously, solid particles pick up momentum from the combustion gases and propagate in the blast wave [8]. The solid particles in the blast wave contribute to heat transfer from the reaction and increase the far-field temperatures [9].…”

“…The most common fuel used is aluminum (Al) due to its high heat of combustion in an oxygen environment (ca. 32 kJ g À1 ) [8]. The significance of using nano Al instead of mm-sized Al is that a reduction in the size results in an increase in the ignition sensitivity and reaction rates by several magnitudes [15,16].…”

Combustion in Afterburning Behind Explosive Blasts

“…In this paper we will present the work done by authors in the field of CGS of afterburning, which includes single and multi-phase afterburning of trinitrotoluene (TNT) w/o aluminium at different HoB [1,2], (Fig. 1) as well as multi-phase afterburning of nitromethane (NM)/steel in a spherical sector domain [3,4] (Fig. 2).…”