Bulletin of the American Physical Society
22nd Biennial Conference of the APS Topical Group on Shock Compression of Condensed Matter
Volume 67, Number 8
Monday–Friday, July 11–15, 2022; Anaheim, California
Session M01: Novel Modeling ApproachesRecordings Available
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Chair: Abigail Hunter, Los Alamos National Laboratory Room: Anaheim Marriott Platinum 5 |
Tuesday, July 12, 2022 4:00PM - 4:15PM |
M01.00001: SDT Behavior of Functionally Graded Energetic Materials (FGEM) Daniel H Olsen, Min Zhou, Von Whitley The behavior of energetic materials is significantly influenced by the spatial distributions of microstructure heterogeneities and voids. We propose the concept of Functionally Graded Energetic Materials (FGEM) whose microstructure features (grain size, grain volume fraction, void size, and void volume fraction) change spatially such that they may allow the behavior of the materials to be tailored. Here, we use gradients in the density of voids to alter the detonation behavior of a polymer-bonded explosive with attributes echoing those of PBX9501. Three-dimensional mesoscale simulations are carried out. Microstructures are designed to have different void densities and void density gradients. The analyses focus on the shock-to-detonation transition (SDT) behavior and the run distance. Four cases with different graded microstructures are considered. An HVRB model is used to account for the decomposition of the HMX crystals. The calculations show that the gradient of the void density significantly affects the run distance, the propagation of the shock and reaction fronts, and the rate at which the SDT transition is achieved. Overall, the findings point out that microstructure feature gradients can be viable variable for manipulating the behavior of energetic materials. |
Tuesday, July 12, 2022 4:15PM - 4:30PM |
M01.00002: Applications of chemical kinetics to detonation: Wave coalescence and homogeneous initiation in single crystal 1,3-propanediol-2,2-bis[(nitrooxy)methyl]-tetranitrate (PETN) Bryan F Henson, Laura Smilowitz A thermal ignition model is used in parallel with single crystal solid and product fluid Equations of State (EOS) from the literature to calculate the time and distance to homogeneous shock initiation in single crystal PETN. The ignition model is a highly constrained, globalized representation of the temperature and pressure dependent decomposition chemistry of PETN. Initiation in the single crystal proceeds via a homogeneous initiation mechanism where thermal ignition results from a well-defined initial shock state (P,T,V). The transition to steady detonation at an observed location (x*, t*) then follows when a superdetonation wave initiated by this thermal ignition overtakes the input shock wave. In the traditional approach P and V are determined directly from measurements, leaving T relatively unconstrained due to the extremely nonlinear dependence of T on P, V in the EOS. We present an iterative algorithm that captures and clearly separates these phenomena by calculating T as a function of P from the chemical kinetics of the thermal ignition. This allows the determination of the input shock state (P,T,V) without recourse to typical assumptions of energy and momentum conservation across an infinitely thin shock discontinuity or constraints on the entropy change. The calculated states compare favorably with pressures and states of compression observed in experiment but provide a new and interesting set of temperatures associated with each state. We discuss these fully determined initial shock states in (P, V, T) in the context of PETN thermodynamics, specifically the solid/liquid phase boundary at high temperature and pressure. |
Tuesday, July 12, 2022 4:30PM - 4:45PM |
M01.00003: Initial temperature effects on the shock initiation of high explosives Lee Perry The initial temperature of a high explosive affects its shock initiation behavior. This may occur due to thermal expansion that induces microstructural changes, or because of direct effects on the chemical reaction rates. In this work, we explored the root cause using a physics-informed reactive flow model, the so-called Physically-Informed Scaled Uniform Reactive Flow model (πSURF). In previous work, we have used the model to gain insight into the role of porosity and pore size distribution in explosive performance. The model invokes the concept of the temperature- and size-dependent critical ‘hot-spot’, which in turn allows us to evaluate the fraction of the porosity ignited for a given shock strength. We can therefore also see the effect of initial temperature by estimating the change in the critical hot spot conditions at an elevated initial temperature. Here, we explore the model predictions for the explosive PBX 9501 at an initial temperature of 150 C in the form of the time- or distance-to-detonation and compare the results to experimental data. We found a favorable comparison. The model suggests the elevated temperature reduces the critical hot spot size, allowing a given shock strength to ignite a larger fraction of the porosity, relative to ambient temperature. |
Tuesday, July 12, 2022 4:45PM - 5:00PM Withdrawn |
M01.00004: Development and Analysis of a Multiphase Model-Informed Closure Relation for Steady Detonation Behavior of Energetic Materials Michael Crochet The steady detonation behavior of energetic materials (EM) in response to shock loading is a key component of performance characterization. The reactive Euler equations serve as the theoretical foundation of many hydrocodes that are used to predict the behavior of EM at engineering scales. An expression referred to as a closure relation is required to ensure a unique solution to the system equations. However, the form of this closure relation, as well as its ability to faithfully represent the underlying physics, continues to be a topic of significant debate within the energetics community. Unlike traditional pressure-dependent reactive burn models such as ignition-and-growth, the use of more recent models for energetics may lead to inaccurate predictions if the selection of closure relation is not appropriate. Here, we discuss the results of a unified mixture/multiphase modeling framework to express the closure relation in terms of simplified inter-constituent interactions. This allows us to pose a new closure relation that better reflects the transport processes between mixture components. We examine the effects of this new closure model on the reaction zone structure for ideal and non-ideal EM, and compare the results to those using conventional closures. |
Tuesday, July 12, 2022 5:00PM - 5:15PM |
M01.00005: Implicit Shock-Fitting of Detonations in Condensed Explosives Andrew Corrigan, Jason F Hackl, Brian D Taylor, David R Mott We present numerical simulations of steady and unsteady detonations using the Moving Discontinuous Galerkin with Interface Condition Enforcement (MDG-ICE) method. MDG-ICE is an implicit shock-fitting method that detects, tracks, and fits all shocks and material interfaces as well as fine-scale features such as reaction zones by treating the mesh as a variable within an optimization framework. Unsteady problems are cast into a space-time formulation in order to accommodate material interface-shock interactions with non-trivial and dynamic topology. We apply MDG-ICE to the simulation of multi-dimensional unsteady detonation problems using realistic equations of state and material strength models. We assess its ability to detect, fit, and track shock waves and thin reaction zones in the high explosive as well as the material interface with an inert confining material along with all reflected and transmitted waves. We will quantify the resulting reduction in grid resolution requirements in comparison to traditional hydrodynamic methods as well as the overall simulation time compared to production hydrocodes. |
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