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The disparity between the reaction and the engineering length scales in high-explosive (HE) systems motivates the use of programmed burn methods where the detonation wave is replaced with a surface and an evolution equation. When the normal detonation velocity differs from the nominal Chapman–Jouguet value (non-zero curvature), the local expansion isentrope of the HE detonation products must be mathematically consistent with the post-flow state to yield the correct detonation energy. The hydrodynamic step associated with the HE energy release is typically treated using a velocity-adjusted equation of state or a pseudo-reaction zone model. This paper describes a model where the bulk of the chemical energy is released instantaneously at the shock and the remainder is released at the finite rate dictated by a base reactive burn model. The implementation steps rely on existing code infrastructure and use the same parameter calibration as the base burn model. Two one-dimensional test cases are presented for a spherically diverging and a spherically converging detonation. The results show that the proposed methodology is able to capture the main flow features at coarse resolutions while retaining a strong hydrodynamic coupling. [ABSTRACT FROM AUTHOR]

The aquarium test provides optical data on important aspects of detonation performance, namely the detonation velocity, shock wave shape in the surrounding water, and expansion rate of the condensed phase explosive products. It is commonly used for calibrating reaction rate laws and products equations of state (EOS). An important aspect, with regards to the analysis, is an adequate representation of the confining material to avoid inaccuracies. We conduct a series of two-dimensional axisymmetric reactive flow simulations for an ANFO-PMMA-water system using the Ghost Fluid Method. The goal is to evaluate the results obtained using three different EOSs for water: Tait, Murnaghan, and Tillotson. The numerical calculations are compared to large-scale aquarium experiments where the HE-water interface and the water shock front locations are directly measured from time-resolved image data. [ABSTRACT FROM AUTHOR]

We present a new Eulerian multi-material hydrodynamics code to simulate the mechanics of impact crater formation. It is based on the open source astrophysical radiation magnetohydrodynamics with adaptive mesh refinement code ATHENA++. The hydrodynamics method is a directionally unsplit, high-resolution shock capturing Godunov scheme. We have developed and implemented a new multi-material capability into ATHENA++, where the evolution of several materials (gas and/or solids) is modeled in a fluid approximation with a set of conservative equations coupled to the basic hydrodynamic equations. Each material is governed by a separate equation of state (EOS) where we assume pressure equilibrium closure for mixed cells. The current implementation includes analytic EOS, but an extension to tabular form is straightforward. In this paper, we describe the numerical method and apply it to early-time models of asteroid impacts into layers of water and granite. Each layer is modeled using a Mie-Gruneisen EOS based on experimental shock data. We focus the study on oblique shocks and compare simulation results with analytic solutions from shock polar analysis. We discuss the coupling to strength and fracture models with this code. [ABSTRACT FROM AUTHOR]

A calibration of the AWSD (Arrhenius Wescott-Stewart-Davis) reactive flow model, applied to the HMX based explosive PBX 9501 is presented. Requisite equation of state parameters for the high explosive reactants and products are based on a combination of experimental data and theoretical calculations. The experimental data needed to calibrate the reaction rate model, specifically shock to detonation transition and detonation propagation at a variety of initial temperatures, are presented along with model results and planned future activities. [ABSTRACT FROM AUTHOR]

A set of experiments was designed to measure the Hugoniot for the overdriven products equation of state (EOS) of PBX 9501 to extend data from which current EOS models draw. A series of shots was conducted by M-9 using the two-stage gasguns at LANL. The experiments were modeled in FLAG, a Langrangian multiphysics code, using a one-dimensional setup which employed the WSD reactive burn model. A comparison of the modeled results to the experimental data reveals that the model is a good fit to the data in the lower pressure region. However, in the upper pressure region, the WSD results do not represent the data as well as in the lower regions. This is an indication that the model could be modified to more accurately reproduce data in all regions. [ABSTRACT FROM AUTHOR]