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 C4: MS: EOS Development |
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Chair: Frank Cherne, LANL Room: Pavilion West |
Monday, June 17, 2019 11:00AM - 11:15AM |
C4.00001: Tabulating a Multiphase Equation Of State Geoffrey Cox In a hydrocode simulation the knowledge of pressure as a function of density and energy is needed to solve the hydrodynamic equations. This is obtained from the equation of state (EoS) of a material. For routine use the EoS should be accurate, time efficient, and robust. It is thus advantageous for complex models to tabulate the EoS beforehand, and during the hydrocode simulation to interpolate (or extrapolate) using this grid. A common EoS table format is the SESAME format developed at LANL. However, when this format was developed EoS models that accurately capture the discontinuous changes seen with phase transitions were not commonplace. This talk describes additions to the SESAME format that provide a route for tabulating a multiphase EoS. The final product is found to give an accurate and robust response as well as having an acceptable time penalty. [Preview Abstract] |
Monday, June 17, 2019 11:15AM - 11:30AM |
C4.00002: Multiphase EOS development at LLNL -- improving EOS fidelity by collective knowledge of experiment and theory: the cases of Beryllium {\&} Gallium Christine Wu, Carrie Prisbrey, Joel Varley Equation of state (EOS) describes how materials respond to changes in energy, pressure, density, and temperature. The availability and quality of EOS are vital for achieving realistic hydrodynamic simulations. Over the past few years, we have successfully developed an object-oriented multiple EOS generation code (MEOS) at LLNL, which substantially reduces turn-around time in multiphase EOS generation, and provides a wide collection of EOS models. With this new tool, we began an accelerated effort at LLNL to develop global EOSs in the multiphase representation. First, we started with the metals of Beryllium (Be) and Gallium (Ga). Be is a potential ablator material for NIF experiments, and Ga has an unusual liquid phase that is denser than the Ga-I solid phase leading to a melt line of negative slope near ambient conditions. Recent dynamic experiments at Z also show interesting features of phase transitions in Ga. In this work, we present our construction of the baseline multiphase models for Be and Ga utilizing the collective knowledge of experiment and first principle's DFT calculations. In addition, we will discuss our preliminary effort to assess EOS uncertainties, in particular our study of DFT uncertainties due to the choice of exchange-correlation functions. [Preview Abstract] |
Monday, June 17, 2019 11:30AM - 11:45AM |
C4.00003: Verification of Uncertainty Propagation for Equation of State Tables John H. Carpenter, Allen C. Robinson, Bert Debusschere Costly equation of state (EOS) models are often tabulated to improve the performance of physics codes. Given a parametric representation of the uncertainty in an EOS, one must then deliver a set of tables that reproduces that uncertainty for forward propagation through the physics codes. Two candidates for a practical and efficient delivery method are a reduced set of table samples from a Markov Chain (MC) and a compressed table generated using Principal Component Analysis (PCA). These methods are verified through a simulation of an exploding wire using an aluminum EOS. The MC sample route is found to be superior, with PCA tables failing to provide sufficient accuracy with a reasonable number of modes for problems with realistic complexity. \\ \\ {*}Sandia National Laboratories is a multimission 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. [Preview Abstract] |
Monday, June 17, 2019 11:45AM - 12:00PM |
C4.00004: Using experimental uncertainties to build uncertainty aware material models for extreme conditions Richard Kraus, Suzanne Ali Using sophisticated hydrodynamic codes, we can model events from giant impacts during planetary formation to inertial confinement fusion implosions. The degree to which these simulations predict reality, however, is dependent on how well we understand the materials and physics involved. We need material models that both accurately represent the experimental data and that also communicate the uncertainty in the experimental measurements. We have constructed a framework for using both experimental measurements and the associated experimental uncertainties to construct equation of state models that communicate not only current best measurements, but also the accuracy of those measurements. This method had been used to construct an ensemble of wide-ranging equation of state models for copper that reflect the experimental uncertainties in the data used to construct the table. This work was performed under the auspices of the U.S. Department of Energy by Lawrence Livermore National Laboratory under Contract DE-AC52-07NA27344. [Preview Abstract] |
Monday, June 17, 2019 12:00PM - 12:15PM |
C4.00005: Improved hard sphere radial distribution function in the CRIS equation of state model Benjamin Cowen, John Carpenter Experiments and theory have been refined for decades in order to better approximate thermodynamic properties of materials. These thermodynamic properties are stored in equation of state (EOS) models, and used as input, such as SESAME tables, into higher level shock physics codes. To ensure the integrity of these codes, the accuracy of the EOS models is paramount. The CRIS (Corrected Rigid Spheres) EOS model [1], developed from fluid perturbation theory using a hard sphere reference system, has been successfully used to calculate the EOS of many materials, including gases and metals. The hard sphere radial distribution function (RDF) plays a pivotal role in choosing the hard sphere diameter, through a variational principle, as well as the thermodynamic response. Despite its success, the CRIS model has some shortcomings in that it predicts too large a temperature for liquid-vapor critical points, and breaks down at large compression. To remedy these limitations, we demonstrate the effects of an improved analytical representation of the RDF. [1] G. I. Kerley, J. Chem. Phys. 73, 478 (1980). [Preview Abstract] |
Monday, June 17, 2019 12:15PM - 12:30PM |
C4.00006: Automated fitting of a semiempirical multiphase equation of state for carbon Kirill Velizhanin, Joshua Coe The equation of state (EOS) of carbon is important in high explosive, geophysical, and inertial confinement fusion applications. Within the semiempirical Sesame framework, the EOS of each phase is represented by a sum of cold, ionic, and thermal electronic Helmholtz free energy contributions. Each phase has ~5-10 independent parameters that are adjusted to reproduce single-phase data (e.g., thermal expansion, isothermal compression) as well as experimentally- and computationally-derived phase boundaries. Manual calibration of the full multiphase EOS (i) is arduous, and (ii) complicates (if not prohibits) rigorous uncertainty quantification. We present our progress in development and implementation of automated EOS parameterization based on minimization of a cost function. This function encodes deviation of EOS results from their experimental and computational benchmarks. Optimization is implemented as a combination of global (particle swarm) and local optimization techniques. Accuracy of the resulting multiphase carbon EOS, choice of the cost function, and uncertainty quantification will be discussed. [Preview Abstract] |
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