Bulletin of the American Physical Society
15th APS Topical Conference on Shock Compression of Condensed Matter
Volume 52, Number 8
Sunday–Friday, June 24–29, 2007; Kohala Coast, Hawaii
Session Q7: Post Detonation Effects |
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Chair: David Frost Room: Fairmont Orchid Hotel Promenade III |
Thursday, June 28, 2007 1:45PM - 2:00PM |
Q7.00001: Factors Affecting Internal Blast Richard Granholm, Harold Sandusky, Joshua Felts Internal blast refers to explosion effects in confined spaces, which are dominated by the heat output of the explosive. Theoretical temperatures and pressures may not be reached due to heat losses and incomplete gas mixing. Gas mixing can have the largest effect, potentially reducing peak quasi-static pressure by a factor of two due to lack of thermal equilibrium between products and atmosphere in the space, without including the incomplete combustion of excess fuel when that atmosphere is air. Chamber and test geometry affect gas mixing, which has been inferred through a number of experimental techniques and compared to calculations, for both large- and small-scale tests. Observations of late-time combustion depend on the extent of mixing and whether the excess fuel is gaseous or aluminum particles. [Preview Abstract] |
Thursday, June 28, 2007 2:00PM - 2:15PM |
Q7.00002: Cylindrical Explosive Dispersal of Metal Particles R.C. Ripley, L. Donahue, Y. Horie, C.M. Jenkins, F. Zhang The explosive dispersal of densely-packed metal particles in cylindrical RDX-based charges is studied numerically. Simulations are conducted using a reactive multiphase fluid-dynamic code. Spherical tungsten particles are applied in high metal mass fraction cylindrical charges in two configurations: a particle matrix uniformly embedded in a solid explosive versus an annular shell of particles surrounding a high-explosive core. The effect of particle number density is investigated by varying the nominal particle diameter from 27 to 120 $\mu $m while maintaining a constant metal mass fraction. Results are compared with steel particles to evaluate the influence of material density on dispersal. To account for early-time particle loading, momentum acceleration factors for shock interaction with packed metal particles are employed. The near-field dense granular heterogeneous flow effect is included in the governing equations and drag model; in the far-field, drag is the main driving force within the expanding detonation product gases and air. The dispersal dynamics are observed at radial locations in terms of arrival time, velocity and particle concentration. Results from experimental trials, described in the companion paper ``Kinetic and Particle Characterization in Explosively-Driven Two-Phase Flow using PIV'' by Jenkins \textit{et al}., will ultimately be used to improve empirical-based drag models for dense supersonic multiphase flow. [Preview Abstract] |
Thursday, June 28, 2007 2:15PM - 2:30PM |
Q7.00003: Post-Detonation Energy Release from TNT-Aluminum Explosives Fan Zhang, John Anderson, Akio Yoshinaka Detonation and post-detonation energy release from TNT and TNT-aluminum composite have been experimentally studied in an air-filled chamber, 26~m$^{3}$ in volume and 3~m in diameter. While TNT has a high oxygen deficiency, experiments with 1.1 kg~to 4~kg charges yield energy releases reaching only 86{\%} of theoretical equilibrium values, possibly due to the non-uniform mixing between the detonation products and air. In order to improve mixing and further increase afterburning energy, large mass fractions of large aluminum particles are combined with TNT. The effect of particle distribution is also investigated in two composite configurations, whereby the aluminum particles are uniformly mixed in cast TNT or arranged in a shell surrounding a TNT cylinder. It is shown that the TNT-aluminum composite outperforms pure TNT, while improved performance is achieved for the shell configuration due to enhanced spatial mixing of hot fuels with oxidizing gases. Comparisons with the equilibrium theory and a liquid-based aluminized composite explosive (with an oxygen deficiency less than that of TNT) are conducted to further explore the mixing and afterburning mechanism. [Preview Abstract] |
Thursday, June 28, 2007 2:30PM - 2:45PM |
Q7.00004: Effect of shock compression on aluminum particle reaction in condensed media Akio Yoshinaka, Fan Zhang While it is known that aluminum particles, when mixed with an explosive, can react with detonation products and air, the effect that the detonation front has on the onset of aluminum reaction is not well understood. Past experiments have shown a dependence of particle reaction start time on confinement; reaction for 1-10~micrometer particles occurs 1-10~microsec behind the detonation front. It is speculated that oxide layers are compromised by the detonation front and particle morphology changes significantly upon detonation passage. Of particular interest is the extent to which the presence and concentration of surrounding materials (e.g., binder, explosive, {\ldots}) can influence the removal of the thin oxide layer encapsulating each particle. Samples consisting of aluminum powder tens of microns in diameter and mixed with an inert condensed phase additive were shock compressed through flyer plate impact to pressure levels comparable to those encountered during detonation (15-20~GPa). To confirm the extent to which particles react with detonation products, particle beds saturated with explosive were tested under similar conditions. Each sample, confined within a hermetically sealed test cell, was recovered after the experiment for microscopic analysis. The effects of particle size and particle-to-additive ratio were investigated as well. [Preview Abstract] |
Thursday, June 28, 2007 2:45PM - 3:00PM |
Q7.00005: Detailed Comparison of Blast Effects in Air and Vacuum J.W. Tringe, J.D. Molitoris, R.G. Garza, H.G. Andreski, J.D. Batteux, L.M. Lauderbach, E.R. Vincent, B.M. Wong We have performed a detailed investigation of blast effects from high-explosive detonations in air and in vacuum. This research was done with 4 kg charges in a large- volume fully contained spherical firing tank. The most obvious consequence of detonation in vacuum is that prompt shock effects are negated as the detonation has no external medium for coupling. The nature of the fireball is also completely altered due to the lack of surface combustion. However, we find that the net effect of the blast on large area witness plates is remarkably very similar in the air and vacuum environments. Diagnostics for this blast characterization included multiple-view high-speed imaging systems and time resolved pressure data gauges. Experimental results and model simulations will be presented. [Preview Abstract] |
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