Bulletin of the American Physical Society
20th Biennial Conference of the APS Topical Group on Shock Compression of Condensed Matter
Volume 62, Number 9
Sunday–Friday, July 9–14, 2017; St. Louis, Missouri
Session S4: Particulate Matter III: Mesocale Phenomena |
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Chair: Minta Akin, Lawrence Livermore National Laboratory Room: Regency Ballroom A |
Thursday, July 13, 2017 9:15AM - 9:30AM |
S4.00001: Particle Jet Mitigation During Explosive Dispersal of Particles in Concentric Layers Bradley Marr, David Frost, Jason Loiseau, Samuel Goroshin, Quentin Pontalier, Fan Zhang The explosive dispersal of a layer of solid particles surrounding a high-explosive charge generates a turbulent, multiphase flow. The shock-compacted particle layer can fracture into discrete fragments which move radially outwards on ballistic trajectories. The fragments shed particles in their wakes, forming jet-like structures. The tendency to form jets depends on the mass-ratio of the particles to explosive and the material properties of the particles. Brittle ceramic particles and soft, ductile metal particles are more susceptible to forming jets, whereas particles that are comprised of materials with moderate hardness, high compressive strength and high toughness are much less prone to jet formation. In the present study, we examine the effect that concentrically layering two powder species, silicon carbide and steel, at varying volumetric ratios has on the resulting dispersion. It is seen that through the inclusion of an inner layer of “non-jetting” particles (steel), the strength of the initial shock wave can be attenuated and the jetting response of a typically “jetting” (silicon carbide) material can be suppressed. Increasing the initial thickness of the “non-jetting” inner layer further suppresses jet formation until the jetting response is almost completely mitigated. [Preview Abstract] |
Thursday, July 13, 2017 9:30AM - 9:45AM |
S4.00002: An Euler-Lagrange method for compressible multiphase flow with application to water sound suppression Gregory Shallcross, David Buchta, Jesse Capecelatro High-speed jets emit pressure fluctuations capable of damaging equipment and harming individuals in the vicinity of operation. It has been observed that liquid droplet injection reduces the radiated pressure fluctuations. Yet, to date, the dynamic particle-turbulence coupling with the radiated pressure fluctuations remain elusive. In this study, a volume-filtered Euler-Lagrange method is used in which the flow features are resolved on an Eulerian grid, and the particles are tracked individually in a Lagrange manner. This method is validated in a three-dimensional particle-laden shock tube for a series of volume fractions and shock Mach numbers. The results are used to evaluate the fidelity of modeling needed to capture the reported particle spreading rate and pressure distribution. The approach is then applied to simulate water-droplet injection in free-shear flow turbulence. Initial results show reductions in the radiated pressure intensity consistent with existing experimental data. [Preview Abstract] |
Thursday, July 13, 2017 9:45AM - 10:00AM |
S4.00003: Dynamic Compaction of Nickel Powder Examined by X-Ray Phase-Contrast Imaging A. Mandal, B. J. Jensen, A. Iverson Understanding the response of granular materials under dynamic loading is important for many scientific applications. Methods traditionally employed (stress gauges, laser interferometry, post-shock analysis of recovered specimens etc.) to gain insight into the compaction response provide only indirect and limited information about the underlying mechanisms. In this work, we have used a propagation-based x-ray phase-contrast imaging technique to examine in-situ and in real-time the dynamic compaction of nickel (Ni) powders with two different grain sizes (30 and 45 micron) shocked to different peak pressures. In addition to compaction wave velocities in Ni, insight gained from a preliminary analysis of the obtained images will be discussed. [Preview Abstract] |
Thursday, July 13, 2017 10:00AM - 10:15AM |
S4.00004: Formation mechanism of the shock-induced particle jetting Kun Xue Granular shells or rings dispersed by the impulsive shock loadings disintegrate into macroscopic particle agglomerates which soon protrude into particle jets. Predicting the number of shock-induced particle jets requires the knowledge of the formation mechanism of the particle jetting. We carried out the experiments and numerical simulations of the shock dispersal of the semi-two dimensional particle rings using the discrete element method. Both experimental and numerical investigations reveal a two-staged jetting formation process. The first phase features the transition of the homogeneous particle flows to the localized shear flows which are the precursors of the incipient jets. The incipient jets undergo the substantial annihilation. The number of jets equals to the number of incipient jets subtracted by that of eliminated ones. A physics based model has been proposed to account for the number of jet, which formularizes the initiation and the elimination processes of the incipient jets. [Preview Abstract] |
Thursday, July 13, 2017 10:15AM - 10:30AM |
S4.00005: A Level-set based framework for viscous simulation of particle-laden supersonic flows Pratik Das, Oishik Sen, Gustaaf Jacobs, H.S. Udaykumar Particle-laden supersonic flows are important in natural and industrial processes, such as, volcanic eruptions, explosions, pneumatic conveyance of particle in material processing etc. Numerical study of such high-speed particle laden flows at the mesoscale calls for a numerical framework which allows simulation of supersonic flow around multiple moving solid objects. Only a few efforts have been made toward development of numerical frameworks for viscous simulation of particle-fluid interaction in supersonic flow regime. The current work presents a Cartesian grid based sharp-interface method for viscous simulations of interaction between supersonic flow with moving rigid particles. The no-slip boundary condition is imposed at the solid-fluid interfaces using a modified ghost fluid method(GFM). The current method is validated against the similarity solution of compressible boundary layer over flat-plate and benchmark numerical solution for steady supersonic flow over cylinder. Further validation is carried out against benchmark numerical results for shock induced lift-off of a cylinder in a shock tube. 3D simulation of steady supersonic flow over sphere is performed to compare the numerically obtained drag co-efficient with experimental results. A particle-resolved viscous simulation of shock interaction with a cloud of particles is performed to demonstrate that the current method is suitable for large-scale particle resolved simulations of particle-laden supersonic flows. [Preview Abstract] |
Thursday, July 13, 2017 10:30AM - 10:45AM |
S4.00006: Rapid Compression of Granular Systems using Atomistic Molecular Dynamic Simulations Daniel Orlikowski The dynamic material response of porous materials has many challenges in modeling because phase transitions and/or chemical reactions/products may be occuring. In particular the Hugoniot response for a granular system like SiO$_{2}$ compacts and then has a stiffer response compared to a fully dense sample [Trunin 2001]. A continuum modeling has captured the Hugoniot for these type of systems and was suggested that localized shear may induce phase transitions earlier than hydrostatic compression [Grady 2013]. Recently, atomistic molecular dynamics (MD) are starting to investigate these granular-type, porous sytems [e.g. Lane 2014]. Likewise, we use atomistic MD simulations for nanometer sized granules to investigate the underlying mechanism for the SiO$_{2}$ Hugoniot using Tersoff potentials. We first establish a Hugoniot baseline for a single crystal SiO$_{2}$ sytem. Then we use nearly spherical granules of SiO$_{2}$ in differing packing schemes---close-packed to random configurations---controlling the initial number of contact points. We discuss the observed mechanisms during the compacting and subsequent compression of the porous system. This work performed under the auspices of the U.S. Department of Energy by LLNL under Contract DE-AC52-07NA27344. [Preview Abstract] |
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