Bulletin of the American Physical Society
18th Biennial Intl. Conference of the APS Topical Group on Shock Compression of Condensed Matter held in conjunction with the 24th Biennial Intl. Conference of the Intl. Association for the Advancement of High Pressure Science and Technology (AIRAPT)
Volume 58, Number 7
Sunday–Friday, July 7–12, 2013; Seattle, Washington
Session U5: TM Continuum Modeling III |
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Chair: Robert Ripley, Martec Limited Room: Cascade I |
Thursday, July 11, 2013 11:00AM - 11:15AM |
U5.00001: Analysis of Compaction Wave Dissipation in Porous Metalized Explosive Pratap Rao, Keith Gonthier It is well established that the inclusion of reactive metals in explosive formulations can enhance post-detonation energy release but it remains unclear, even for idealized systems, how the composition and microstructure of metal containing porous solid explosives affects dissipative heating within compaction waves that is important for weak initiation of detonation. In this study, we perform inert meso-scale simulations to computationally examine how the initial porosity and metal mass fraction of aluminized HMX influences dissipation within compaction waves and we compare predictions to those given by a macro-scale compaction theory. The meso-scale model uses a hyperthermoelastic-viscoplastic and stick-slip friction theory to track the evolution of thermomechanical fields within individual particles that result from pore collapse within waves. Effective quasi-steady wave profiles are obtained by averaging meso-scale fields over space and time. The macro-scale theory predicts the variation in effective thermomechanical fields within waves due to imbalances in phase-specific pressures and configurational stresses. Qualitative agreement exists between meso-scale and macro-scale predictions. [Preview Abstract] |
Thursday, July 11, 2013 11:15AM - 11:30AM |
U5.00002: Temperature-based model for condensed-phase explosive detonation Nicolas Desbiens, Christophe Matignon, Remy Sorin, Vincent Dubois Simple reactive flow models for condensed explosives have four requirements: two equations of state (EOS), one for the unreacted condensed-phase explosive, and one for its detonation products, a reaction rate law that converts the explosive in products and a mixture rule to compute the biphasic partially reacted states. Generally, the chemical reaction rates are governed by local temperature. Nonetheless, temperature fields are scarcely known, especially in detonating condensed-phase explosives. Hence this quantity is not provided by the usual unreacted explosive EOS with the required accuracy. As a consequence, for shock initiation and detonation phenomena, rate laws are based on easily measurable properties such as pressure, compression or particle velocity. In this work, we build an EOS for a TATB-based explosive that provides a better estimate of the shocked explosive temperature. This EOS is derived from ab initio simulation results of monocristalline TATB. Then the well-known pressure-based WSD reaction rate law is rewritten to be temperature-dependent. This model is expected to give interesting results as regards shock desensitization and initial conditions variations while remaining very accurate for detonation propagation. Preliminary results will be shown. [Preview Abstract] |
Thursday, July 11, 2013 11:30AM - 11:45AM |
U5.00003: Analyses on the Effect of Hot Spot Density on Material Consumption Rate George Levesque, Peter Vitello, Albert Nichols, Gary Friedman, Trevor Willey, Craig Tarver There is an observed effect of an explosives constituent grain size and density on its performance. At the mesoscale, it is the outward burning of hot spots that controls observed performance. While statistical hot spot models can integrate the mesoscale behavior to macroscale simulations, it is unknown what the density of created hot spots is as a function of grain size and porosity. Simulating mesoscale hot spot distributions and varying hot spot density, we discuss the resultant performance as influenced by inter-pore distance and pore distribution. This work performed under the auspices of the U.S. Department of Energy by Lawrence Livermore National Laboratory under Contract DE-AC52-07NA27344. [Preview Abstract] |
Thursday, July 11, 2013 11:45AM - 12:00PM |
U5.00004: Bridging the Scales from Molecular Dynamics to Navier-Stokes: A Model of Nitromethane Christopher Romick, Marc Cawkwell, Tariq Aslam We present recent work on modeling liquid nitromethane from both a molecular dynamics and continuum approach. Bulk properties of liquid nitromethane, including isothermal compression, heat capacities, and viscosity have been computed from a new quantum mechanical interatomic potential and classical force fields. These bulk properties will be used to build a continuum-level model based in the compressible Navier-Stokes equations. The two modeling paradigms will be compared on a number of test problems. [Preview Abstract] |
Thursday, July 11, 2013 12:00PM - 12:15PM |
U5.00005: The confinement effect of inert materials on insensitive high explosives Yutao Sun, Ming Yu The paper aims at investing the confinement effect of inert materials on insensitive high explosives by means of shock polar curve and phenomenological reaction model. The confinement types are categorized by the shock polar theory, which built on the leading shock wave based on the detonation ZND model. If the sonic velocity of the confinement material is less than the CJ velocity of an explosive, the shock polar theory can be utilized. In general, there are several types of interactions that give a ``match'' of the pressure and streamline-deflection across the interface between IHE and confinement material. A two-dimensional Lagrangian hydrodynamic method with three-term Lee-Tarver rate law is used to numerically simulate all types of confinement interactions. The important character of confinement material include: compressibility, thickness, the representative assembled layers, such as bakelite-iron and iron-beryllium. [Preview Abstract] |
Thursday, July 11, 2013 12:15PM - 12:30PM |
U5.00006: Sensitivity and Uncertainty in Detonation Shock Dynamics Parameterization Carlos Chiquete, Mark Short, Scott Jackson Detonation shock dynamics (DSD) is the timing component of an advanced programmed burn model of detonation propagation in high explosives (HE). In DSD theory, the detonation-driving zone is replaced with a propagating surface in which the surface normal velocity is a function of the local surface curvature, the so-called $D_n-\kappa$ relation for the HE. This relation is calibrated by assuming a functional form relating $D_n$ and $\kappa$, and then fitting the function parameters via minimization of a weighted error function of residuals based on shock-shape curves and a diameter effect curve. In general, for a given HE, the greater the available shock-shape data at different rate-stick radii, the less the uncertainty in the DSD fit. For a wide range of HEs, however, no shock shape data is available, and DSD calibrations must be based on diameter effect data alone. With this limited data, potentially large variations in the DSD parameters can occur that fit the diameter effect curve to within a given residual error. We explore uncertainty issues in DSD parameterization when limited calibration data is available and the implications of the resulting sensitivities in timing, highlighting differences between ideal, insensitive and non-ideal HEs such as Cyclotol, IMX-104 and ANFO. [Preview Abstract] |
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