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 O5: BIEP: Ejecta IV |
Hide Abstracts |
Chair: Alison Saunders, LLNL Room: Broadway I/II |
Wednesday, June 19, 2019 11:00AM - 11:15AM |
O5.00001: Ejecta particle breakup modelling Robin Williams, Chris Batha Aerodynamic forces can lead to the breakup of solid or molten ejecta particles moving through gas. This breakup is opposed by the effects of strength and surface tension. We describe the simple model for this process developed by Cowperthwaite, which is based on a single ordinary differential equation for the particle radius, and compare results with the more detailed TAB breakup model developed by O'Rourke and Amsden (1987). \copyright{} British Crown Owned Copyright 2019/AWE [Preview Abstract] |
Wednesday, June 19, 2019 11:15AM - 11:30AM |
O5.00002: The Spike Dynamics Source Model for Ejecta in the FLAG Code Alan Harrison The Lagrangian hydrocode FLAG employs a subgrid model to represent the ejection of particulate mass ("ejecta") from a shocked metal surface. The ejection process is modeled as a Richtmyer-Meshkov instability (RMI) of the liquid metal surface, in which the metal spikes that form break up to become ejecta. The FLAG model includes (1) a description of RMI spike and bubble growth rates and (2) the Self-Similar Velocity Distribution (SSVD) model of the velocity field We report here on the improvement of this model by incorporating (3) a spike breakup treatment based on the Taylor Analogy Breakup (TAB) model, and (4) a new model for the inflow of metal into the base of the spikes. This combination reconciles the evolving shape of the spikes (elongation and thinning) with the inflow, and with the corresponding properties of the bubbles. Since the model describes the motion of each fluid element into and along the spike, and subsequent fragmentation of the spike into ejecta, it predicts not only mass ejection rate but also the sizes and velocities of the particles launched in this process. We describe the new self-consistent model and its implementation in FLAG. We present representative verification and validation calculations. [Preview Abstract] |
Wednesday, June 19, 2019 11:30AM - 11:45AM |
O5.00003: High-Order Lagrangian Hydrodynamics Computations of Surface Perturbations in Shock-Driven Metal Fady Najjar, Leo Kirsch, Rob Rieben Ejecta represent a cloud of the particles being emitted from a free material surface when impacted by a shock. Such ejecta particulates play a key role in a wide variety of natural and engineering applications, including supernovae explosions, asteroid strikes, inertial confinement fusion, and hazards on spacecrafts and satellites due to debris impact. Detailed computations are performed using a high-order Lagrangian hydrodynamics code to understand the generation and evolution of ejecta from imposed surface perturbations. Specifically, we utilize the high-order finite-element Arbitrary Lagrangian-Eulerian (ALE) capability of MARBL, a next-generation multi-physics code in development at LLNL. We studied conical perturbations being impact by strong shocks and the surface evolution creating ejecta particulates. We apply this analysis to a recent experimental campaign on laser-driven ejecta where micron-sized divots have been fielded. We investigate the sensitivity to generate melt-on-release ejecta with platform geometry, mesh refinement, and material type strength model and equations of state. Preliminary simulations show that asymptotic bubble and spike velocities are nonlinear with the divot perturbation’s non-sinusoidal effective-wavelength and corresponding amplitude. [Preview Abstract] |
Wednesday, June 19, 2019 11:45AM - 12:00PM |
O5.00004: Development and validation of a compressible nonlinear growth spike velocity model Jonathan D. Regele, Alan K. Harrison, Marianne M. Francois The Richtmer-Meshkov instability (RMI) is responsible for ejecta production after a shock wave passes through a material interface. RMI theory and models can be used to predict the initial spike velocity and infer the velocity of the ejecta particles produced through the instability. Most models are based on incompressible potential flow theory and cannot account for the difference in behavior caused by strong shock waves. Karkhanis et al. [V. Karkhanis et al., J. Appl. Phys., 2018] developed a model for the asymptotic spike velocity that accounts for compressibility. However, particle trajectories are more accurately captured when accounting for the nonlinear growth dynamics that occur between when the interface is initially shocked and when the spikes reach their asymptotic velocity. In this work, the Karkhanis model is converted into a nonlinear growth framework and validated against experimental data. [Preview Abstract] |
Wednesday, June 19, 2019 12:00PM - 12:15PM |
O5.00005: Influence of the phase transitions of tin on microjetting and ejecta production Olivier Durand, Laurent Soulard, Raphaël Prat, Laurent Colombet We use large scale molecular dynamics (MD) simulations to investigate the influence of the phase transitions of tin on microjetting and ejecta production. These processes occur when a tin crystal containing geometrical free surface defects is shock-loaded. For a few years now, we have been showing the interest of using MD as a complementary approach to the classical one (hydrodynamic) for simulating microjetting. It is indeed at the good scale to capture the physics of fragmentation which occurs at the atomistic scale, and it may also be helpful for analyzing experiments. Until now, the phenomenology of ejection is well understood in the simplest case: when the metal directly melts upon receiving the shock and becomes totally liquid. Here, we go further by integrating in the understanding and the description of the ejection process the presence of non-completely molten regions. We show in particular that when the metal melts on release, solid regions are formed, at the very beginning of the ejection process, as the shockwave interacts with the bottom of the surface defect. This phenomenon causes on late times a strong change of the edge morphology of the ejected sheet of liquid metal; it should also exist at the experimental scale. [Preview Abstract] |
Wednesday, June 19, 2019 12:15PM - 12:30PM |
O5.00006: Modeling reactive conversion of Ce ejecta in H$_2$ and D$_2$ gases J.D. Schwarzkopf, D.G. Sheppard, J.E. Hammerberg, M.M. Schauer, W.T. Buttler, R.K. Schulze Shocked Ce metal in contact with a reactive gas such as H$_2$ or D$_2$ produces a distribution of ejecta particles that react with the gas to form Ce hydrides or deuterides. We present an average particle reaction diffusion model to calculate particle and gas temperatures and reaction fractions. We compare model results with recent HE driven Ce experiments into reactive D$_2$ and non-reactive He gases for a variety of initial gas pressures from 2 to 8 atmospheres at initial temperatures of 300 K. We find consistent agreement with radiance temperature measurements as a function of time using particle distributions from Mie scattering data resulting in Ce deuteride mass conversion fractions in D$_2$ gas of order 10 - 15 $\%$. [Preview Abstract] |
Follow Us |
Engage
Become an APS Member |
My APS
Renew Membership |
Information for |
About APSThe American Physical Society (APS) is a non-profit membership organization working to advance the knowledge of physics. |
© 2024 American Physical Society
| All rights reserved | Terms of Use
| Contact Us
Headquarters
1 Physics Ellipse, College Park, MD 20740-3844
(301) 209-3200
Editorial Office
100 Motor Pkwy, Suite 110, Hauppauge, NY 11788
(631) 591-4000
Office of Public Affairs
529 14th St NW, Suite 1050, Washington, D.C. 20045-2001
(202) 662-8700