Bulletin of the American Physical Society
21st Biennial Conference of the APS Topical Group on Shock Compression of Condensed Matter
Volume 64, Number 8
Sunday–Friday, June 16–21, 2019; Portland, Oregon
Session K1: DSIC: Detonation Modeling II |
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Chair: Nicholas Whitworth, AWE Room: Grand Ballroom I |
Tuesday, June 18, 2019 2:00PM - 2:15PM |
K1.00001: A study of shock initiation experiments for the explosive PBX 9502 using three reactive burn models Matthew Price Shock to detonation transition (SDT) experiments are essential in calibrating and validating reactive burn models for explosives. This work investigates the large collection of SDT test data for the explosive PBX 9502 at ambient temperature that was presented by Gustavsen, Sheffield, and Alcon [Journal of Applied Physics, 99, 114907 (2006)]. We first analyze the experimental data and compare two different methods of determining the shock transition time/distance (namely, the bi-linear method and the single curve method). This reveals some of the uncertainty in estimating shock transition points, which contributes to scatter in Pop plot data. Next, we compare the WSD, AWSD, and SURFplus reactive flow models for a collection of approximately 20 experimental shots using the FLAG hydrocode. Error estimates are used to quantify how well each reactive flow model (and their respective parameter calibrations) performs at predicting the SDT process for a range of loading conditions. Additionally, the importance of mesh resolution and numerical dissipation in SDT simulations will be assessed. [Preview Abstract] |
Tuesday, June 18, 2019 2:15PM - 2:30PM |
K1.00002: Evaluation of XHVRB for Capturing Transition to Detonation as Measured with Embedded Gauges Leah Tuttle, Jeff Lajeunesse, Robert Schmitt, Eric Harstad The Extended History Variable Reactive Burn model (XHVRB), as proposed by Starkenburg [1], uses shock capturing rather than current pressure for calculating the pseudo-entropy that is used to model the reaction rate of detonating explosives. Using shock capturing offers potential improvement for single shock modeling over the historically used workhorse model HVRB [3] in CTH [2], in addition to its extended capabilities for modeling explosive desensitization in multi-shock environments [4,5]. The detailed transition to detonation of PBX9501, as revealed by embedded gauge data [6], is compared to models with both HVRB and XHVRB. Improvements to the comparison of model to test data are shown with XHVRB, though not all of the details of the transition are captured. The methodology for fitting XHVRB is also presented, and the model fit for PBX9501 is given. Sandia National Laboratories is a multi-mission laboratory managed and operated by National Technology {\&} Engineering Solutions of Sandia, LLC, a wholly owned subsidiary of Honeywell International Inc., for the U.S. Department of Energy's National Nuclear Security Administration under contract DE-NA0003525. [1] Starkenberg, IDS 15, p. 908 [2] McGlaun et. al, Int. J. Impact Eng., Vol. 10, p. 351 [3] Kerley, G. I., SNL SAND92-0553, 1992 [4] Tuttle et. al, AIP 1979, 100044 (2018) [5] Tuttle et. al, IDS 16 (in progress) [6] Gustavsen, et. al, IDS12, pg. 530 [Preview Abstract] |
Tuesday, June 18, 2019 2:30PM - 2:45PM |
K1.00003: The Statistical Hot Spot Model: Dimensionality and the Effects of Time-Distributed Nucleation Larry Hill The Statistical Hot Spot (SHS) model examines heterogeneous reaction topology. The basic model assumes that 1) nucleation sites are randomly distributed in space, 2) burn waves initiate simultaneously, and 3) reaction spreads from nucleation sites as sharp, uniformly-sized spherical waves. Here, I consider how the depletion function, $F$, varies as certain assumptions are relaxed. I argue that non-idealities reflect a change in effective dimensionality, $D$, which skews $F$ to the right or left. I further argue that typical HE material microstructures are such as to decrease $D$ from the nominal value of three. This expectation agrees with SURF Reactive Flow Model, which gives better results for cylindrical hot spots than for spherical ones. I explicitly model the effects of time-distributed nucleation rates, and show that the effect tends to $increase$ $D$ from the nominal value of three. This is not to say that increased dimensionality is inconsistent with time-distributed nucleation; instead, the sensitivity of $F$ to time-dependent nucleation is small because, above $D = 3$, $F$ changes very little with $D$. I suggest that $D$ should be treated as a modeling free-parameter, to approximately account for multiple non-idealities. [Preview Abstract] |
Tuesday, June 18, 2019 2:45PM - 3:00PM |
K1.00004: A Morphologically Aware Model for TATB Based Explosives James Gambino, Albert Nichols Predicting the performance and safety of explosive devices relies upon an understanding of the underlying hot spot mechanisms. It has long been known that explosive compositions which only differ in microstructure can have significant variations in initiability and corner turning. Conventional reactive flow models do not incorporate microstructure information and, typically, different parameter sets are developed to account for lot-to-lot variations. We develop a morphologically aware detonation model for TATB based explosives that incorporates pore size distribution data. Pore size data is used to define the number of hot spots that are ignited as a function of the effective plastic strain. The ignition sites then spread throughout a 2D patch defined by a TATB cleavage plane. As the 2D patch burns convectively, the remainder of the explosive is consumed by a laminar burn. Initial burn products react through a pseudo-diffusion-controlled reaction to form the final products. The model parameters controlling the initiation and burning are optimized using Pop-Plot and particle velocity data from nominal experiments. To complete the model, the parameters that govern corner turning behavior are calibrated using data from axisymmetric corner turning experiments. LLNL-ABS-768480 [Preview Abstract] |
Tuesday, June 18, 2019 3:00PM - 3:15PM |
K1.00005: WGT: toward a microstructure-aware reactive burn model Maxime Reynaud, Remy Sorin, Vincent Dubois, Nicolas Desbiens Polymer bounded explosives (PBX) consist of energetic crystals coated in a polymer binder. These materials exhibit a highly heterogeneous microstructure. The initiation of the detonation phenomenon in PBXs is believed to be generated at the microstructure scale through hot spots. Hence, many of the explosives properties are understood as a direct consequence of their microstructure. Mesoscale modeling directly addresses the physics of hot spots formation. Unfortunately, the high computational cost prevents their use on laboratory-sized experiments. In practice, continuum-scale models remain mandatory. We describe a new reactive burn model, named WGT, aimed at representing at the continuum scale some of the complexity of the PBXs microstructure. The initiation regime is driven by the shock temperature and results from a surrogate modeling of the kinetics of heterogeneous nucleation and growth model proposed by Maillet et al. The other regimes follow the formulation of the WSD(T) reactive burn model and are driven by the local temperature. This model was calibrated on data for PBX 9502 available in the literature, such as celerity-curvature laws, popplot data or electromagnetic velocity gauge signals. The model was also tested against desensitization and propagation data. [Preview Abstract] |
Tuesday, June 18, 2019 3:15PM - 3:30PM |
K1.00006: High Explosive Shock Initiation Model Based on Hot Spot Temperature Laurence Fried, Matthew Kroonblawd We describe a new shock initiation model based on the Cheetah thermochemical code. The model is based on a multiple stage picture of the shock initiation process and uses hot spot temperature as an auxiliary variable to control the initial stages of reaction. Unlike using rates controlled by other thermodynamic variables, this approach captures physical sub-zonal differences between the bulk temperature and the substantially higher local hot spot temperature that actually governs ignition chemistry. In the model, a single representative hot spot diameter is chosen and the hot spot temperature is controlled by shock pressure and thermal conductivity. The practical utility of a sub-zonal hot spot temperature model will be discussed, as well as evidence for co-existing hot spot and shear band ignition mechanisms in high explosive shock initiation. [Preview Abstract] |
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