Bulletin of the American Physical Society
16th APS Topical Conference on Shock Compression of Condensed Matter
Volume 54, Number 8
Sunday–Friday, June 28–July 3 2009; Nashville, Tennessee
Session V1: DC-4: Modeling Shock Reactions |
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Chair: Malcolm Cook, QinetiQ Room: Tennessee Ballroom C |
Thursday, July 2, 2009 1:30PM - 1:45PM |
V1.00001: A new D(K) relationship for EDC37 Alexander Hodgson, Brian Lambourn, Caroline Handley The Detonation Shock Dynamics model (DSD) is widely used for the propagation of detonation wave-fronts in hydrocode calculations of polymer bonded explosives. In DSD, a detonation velocity vs. curvature relationship D(K) is used to determine the speed at which the detonation front propagates through the explosive. The D(K) relationship for an explosive is usually obtained from rate-stick wave-curvature data. Recently, Roeske et al. have fired a series of very small rate-stick experiments, using samples of the HMX-based explosive EDC37 machined with a femto-second laser. In this paper, this data is combined with the results of previous 1" and 2" rate-stick experiments, to obtain a new D(K) relationship for EDC37. A wave-shape analysis code is developed which uses weighted least-squares fitting methods which improve on current fitting methods. [Preview Abstract] |
Thursday, July 2, 2009 1:45PM - 2:00PM |
V1.00002: Predicting the effect of explosive porosity on sensitivity using CREST Caroline Handley CREST is a reactive-burn model that uses entropy-dependent reaction rates to model shock initiation and detonation behaviour in plastic bonded explosives. A CREST model for the TATB-based high explosive PBX9502 was published previously at this conference. It is well known that changing the porosity of an explosive, like PBX9502, can dramatically influence its sensitivity. The equation of state used in CREST incorporates the snow-plough model, allowing the porosity of the explosive to be selected at will, while keeping the reaction model constant. In this paper, it will be shown that CREST can predict the change in explosive sensitivity with porosity, as demonstrated by the experimentally determined Pop-plots for TATB. In contrast, it will be shown that pressure-dependent reactive-burn models are unable to predict this porosity effect. [Preview Abstract] |
Thursday, July 2, 2009 2:00PM - 2:15PM |
V1.00003: Towards time dependent DSD Yehuda Partom DSD makes it possible to calculate propagation of expanding detonation shocks without a need to evaluate the flow field behind them. DSD is a quasi steady state model calibrated from detonation breakout curves of steady detonations, usually in sticks. Once calibrated (D (k)), it is applied to non steady expanding detonation shocks with slowly varying shapes. Time dependent D(k) relations were introduced in the past in forms like D(k,dk/dt) or k(D,dD/dt), but were not calibrated or applied to realistic detonation situations. In this paper we check predictions of DSD in a spherical outgoing detonation, which is non-steady, by comparing them to reactive flow calculations. From the results we conclude that: 1) for each initial state (in D(R) plane, say) we get a different shock path. All shock paths converge for large R; 2) detonation acceleration dD/dt depends on detonation velocity through: dD/dt=A(Dcj-D), where A depends on the initial radius; 3) the various detonation shock paths do not coincide with the D(k) relation obtained by solving the eigen value problem of quasi steady detonation in spherical symmetry. [Preview Abstract] |
Thursday, July 2, 2009 2:15PM - 2:30PM |
V1.00004: Toward Improved Fidelity of Thermal Explosion Simulations Albert Nichols, Richard Becker, Alan Burnham, W. Michael Howard, Jarek Knap, Aaron Wemhoff We present results of an improved thermal/chemical/mechanical model of HMX based explosives like LX04 and LX10 for thermal cook-off. The original HMX model and analysis scheme were developed by Yoh et.al. for use in the ALE3D modeling framework. The improvements were concentrated in four areas. First, we added porosity to the chemical material model framework in ALE3D used to model HMX explosive formulations to handle the roughly 2{\%} porosity in solid explosives. Second, we improved the HMX reaction network, which included the addition of a reactive phase change model base on work by Henson et.al. Third, we added early decomposition gas species to the CHEETAH material database to improve equations of state for gaseous intermediates and products. Finally, we improved the implicit mechanics module in ALE3D to more naturally handle the long time scales associated with thermal cookoff. The application of the resulting framework to the analysis of the Scaled Thermal Explosion (STEX) experiments will be discussed. [Preview Abstract] |
Thursday, July 2, 2009 2:30PM - 2:45PM |
V1.00005: Non-ideal detonation behaviour of PBX 9502 Stefan Schoch, Nikos Nikiforakis Numerical experiments are performed investigating the non-ideal detonation behaviour of PBX 9502 in two setups. In the first setup we consider a three-dimensional rate stick experiment. A booster charge initiates a reaction front leading to a curved detonation wave. The numerical results are compared to theory and experimental evidence. The effects of weak and strong confinement are discussed. The second setup considers the so called ``hockey puck experiment.'' Experimental results show the appearance of a dead zone due to the effect of the geometry. This is captured by the numerical results, which also reveal that the initially spherical detonation is diffracted leading to local detonation failure. The numerical simulations are performed by solving a mathematical model for a three-phase medium based on the Euler equations. The numerical results are obtained using high-resolution shock-capturing methods combined with adaptive mesh refinement. [Preview Abstract] |
Thursday, July 2, 2009 2:45PM - 3:00PM |
V1.00006: Detonation Structure for Unstable Waves in Condensed Phase HE Charles Kiyanda, Mark Short In gases, propagating detonations develop a distinct three-dimensional cellular structure, characterized by triple point shock (Mach, incident and transverse) interactions that propagate transverse to the front. An oblique shock polar theory for equations of state appropriate to a mixture of gaseous reactants confirms the existence of such triple shock structures for detonation velocities appropriate to gases. A stability analysis of detonation for some EOS and reaction models appropriate to condensed phase systems have also indicated the possibility of unstable non-planar detonations; however an oblique shock polar analysis indicates that triple shock configurations may not be feasible. High resolution numerical simulations are used to examine the structure of condensed phase unstable detonations in such cases. [Preview Abstract] |
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