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 P02: Shock Initiation of MaterialsRecordings Available
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Chair: Leora Dresselhaus-Marais, Lawrence Livermore Natl Lab Room: Anaheim Marriott Platinum 6 |
Wednesday, July 13, 2022 11:00AM - 11:15AM |
P02.00001: Comparison of Reactive Flow Equilibrium Closure Assumptions in CTH Kevin Ruggirello, Leah W Tuttle, David Kittell An equilibrium closure assumption is typically made in hydrocodes for reactive flow models between the unreacted and product equations of state. In the CTH (not an acronym) shock physics code the assumption of density and temperature equilibrium is made by default, whereas most other codes make a pressure and temperature equilibrium assumption. The main reason for this difference is the computational efficiency in making the density and temperature assumption over the pressure and temperature one. With parameters fit to data, either assumption can be used accurately predict reactive flow response using the various models. However, the model parameters fit based on one assumption cannot necessarily be used directly in the same model with a different closure assumption. A new framework is introduced to allow this assumption to be changed independently within CTH for each reactive material. Comparisons of the response and computational cost of the reactive flow models with the different equilibrium assumption will be presented for two of the most heavily used models - History Variable Reactive Burn (HVRB) and Ignition and Growth (IG). The comparison will be conducted for PBX9501 for 1D plate impact, and simple 3D problems. |
Wednesday, July 13, 2022 11:15AM - 11:30AM |
P02.00002: Improvement in Explosive Performance Modeling with xHVRB Leah W Tuttle, Jeff W LaJeunesse History Variable Reactive Burn (HVRB) has been a work horse model in CTH for shock-to-detonation transition simulations. xHVRB was proposed by Starkenberg [1] to capture more advanced reactive flow phenomena like explosive desensitization by extending HVRB to use captured shock pressure in addition to current pressure and introducing a pseudo-entropy term that can account for explosive pre-shock. xHVRB has been demonstrated to capture desensitization in multi-shock scenarios [2]. In this study, xHVRB is tested across other explosive phenomena: diameter effect, failure diameter, corner turning and thin pulse initiation. xHVRB shows an improvement in capturing additional explosive behaviors, including better detonation stability which is crucial for corner turning and diverging detonations in insensitive explosives. |
Wednesday, July 13, 2022 11:30AM - 11:45AM |
P02.00003: Optimum Product Freeze Temperatures For Analytic Cylinder Velocity Calculations Leonard Stiel, Philip J Samuels, Ernest L Baker, David A Rydzewski Cylinder velocities calculated with the Baker analytic cylinder model utilizing JWL parameters generated from the Jaguar thermochemical equilibrium program with a nominal 2200 K product reaction freeze temperature have been found to be generally in agreement with experimental streak data to within 2% at high expansions. However, analyses of recent cylinder test data obtained by PDV procedures indicate larger deviations at high expansions for values calculated with these procedures, with an average positive deviation of about 3% at 7 area expansions. A previous study has suggested that higher freeze temperatures are required for highly nonideal explosives such as TNT. In order to investigate the effects of the freeze temperature and corresponding oxygen balance for optimum agreement with cylinder velocity PDV values, results for a number of standard formulations have been analyzed in detail. The formulations include HMX or RDX -based systems and literature data for a Cl-20 based explosive LX-19. Ratios of calculated to experimental cylinder velocities for the HMX and RDX formulations decrease with increasing freeze temperature in the range 2200 K to 3000 K. There is no apparent trend with oxygen balance for these explosives, but the ratio for the more ideal LX-19 explosive is close to 1.0 for the entire temperature range. For the explosives considered the average error between calculated and experimental velocities is reduced to under 1% at 7 area expansions with a 3000 K freeze temperature. |
Wednesday, July 13, 2022 11:45AM - 12:00PM |
P02.00004: Transverse Initiation and Wavefront Breakout at High Explosive Interfaces. Alison Kubota, Bradley W White, Sorin Bastea, Robert Reeves Interactions between high explosives (HE) of differing detonation behaviors is complex. Simulations and experiments are presented that explore the transverse shock initiation in rate sticks of two adjacent slabs of explosives of different explosives. Each HE layer is either a higher performance, HMX-based explosive, a lower performance, TATB-based explosive, or a blend of the two. In this configuration, the slab with the faster detonation velocity transversely initiates the slower high explosive side thus driving the phase velocity of the entire rate stick, producing a wavefront breakout shape that captures details of the transverse initiation in the slower detonation velocity side. From the measured experimental detonation velocities measured and wavefront breakout profiles captured with streak imaging, optimized rate parameters for the reactive flow model [RRV1] were calculated. The performance of the optimized model is reported over the entire set of rate stick composition pairs. |
Wednesday, July 13, 2022 12:00PM - 12:15PM |
P02.00005: Downstream Effects of Particle Clustering in Heterogeneous Powder Mixtures under Shock Compression Manny Gonzales, Daniel Rhoads, Nathan Levkulich, Katelun Wertz Heterogeneous, multiphase materials with topological complexities manifest changes in the shock compression process which can induce localization effects in small neighborhoods, as well as downstream effects carried by the propagating wave. Local property contrasts in packed particle beds induced by the clustering of particles of the same phase magnify the propensity for flow instabilities via plastic extrusion through harder material in the proximity of the compressed particles. These effects modify the shock wave and therefore affect the bulk thermodynamic state achieved by the compacted shock compressed particles. Pressed powder compacts can show preferential particle clustering due to the manufacturing process and even small changes in clustering can lead to large differences in localization and final predicted equation of state. The effects of particle clustering and other heterogeneities in the microstructure of pressed powder compacts are investigated in this work via microstructural descriptor functions and microstructure-based simulations of the shock compression phenomena in real and synthetic microstructures. Distinct microstructures with the same stoichiometry of phases but different particle clustering distributions are compared based on their wave profiles, density of hot spots/flow structures, and evolving correlation functions that fully describe the microstructural features of interest. This preliminary work will show the importance of fully quantifying local effects vs. volume/mass-weighted homogenized properties when predicting the performance of a specific heterogeneous material composition. |
Wednesday, July 13, 2022 12:15PM - 12:30PM |
P02.00006: High-order schemes for simulation of shock-interface interactions in micro-structured materials. Chukwudubem O Okafor, H.S. Udaykumar The response of materials to high strain rate loading is important in applications such as high-speed impact and penetration, high speed flows with particles and shocked flows in multi-material media. For example, the thermomechanical response of energetic materials (EMs) to shock loading is used to characterize their sensitivity. The initiation of EMs depends on shock interactions with their complex microstructure (void spaces/defects and crystal-crystal interfaces). Previous studies have employed at best 3rd-order accurate numerical schemes for shock simulations in EMs, requiring well-resolved simulations to obtain grid-independent solutions. High-order accurate methods can provide an improved balance between computational time and accuracy of calculations. Here, a non-characteristic 5th-order WENO scheme is used to study the response of materials with complex internal structure under shock loading using an Eulerian framework. The high-order scheme is combined with levelsets to define interfaces and a HLLC (Harten,-Lax-van Leer-Contact) approximate Riemann solver is employed to eliminate numerical oscillations and maintain high-order reconstruction across the sharp interface. Test problems involving high speed impact, shocks, elastic-plastic flows and interfaces are used to evaluate the accuracy, computational cost, and performance of the high-order methods. The new techniques provide unprecedented resolution of both embedded interfaces and their dynamics, as well as resolution of shock systems and reaction fronts. |
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