Publications

Proposed for publication in Computers & Fluids.

Rider, William J.; Love, Edward L.; Scovazzi, Guglielmo S.

Abstract not provided.

Kamm, James R.; Rider, William J.

We present a new model for closing a system of Lagrangian hydrodynamics equations for a two-material cell with a single velocity model. We describe a new approach that is motivated by earlier work of Delov and Sadchikov and of Goncharov and Yanilkin. Using a linearized Riemann problem to initialize volume fraction changes, we require that each material satisfy its own pdV equation, which breaks the overall energy balance in the mixed cell. To enforce this balance, we redistribute the energy discrepancy by assuming that the corresponding pressure change in each material is equal. This multiple-material model is packaged as part of a two-step time integration scheme. We compare results of our approach with other models and with corresponding pure-material calculations, on two-material test problems with ideal-gas or stiffened-gas equations of state.

Computer Methods in Applied Mechanics and Engineering

Shadid, John N.; Love, Edward L.; Rider, William J.

Abstract not provided.

Kamm, James R.; Weirs, Vincent G.; Swiler, Laura P.; Adams, Brian M.; Rider, William J.; Eldred, Michael S.

Abstract not provided.

Weirs, Vincent G.; Carnes, Brian C.; Dinzl, Derek J.; Howard, Micah A.; Kieweg, Sarah K.; Ray, Jaideep R.; Rider, William J.; Smith, Thomas M.

Abstract not provided.

Crozier, Paul C.; Howard, Micah A.; Rider, William J.; Freno, Brian A.; Bova, S.W.; Carnes, Brian C.

The SPARC (Sandia Parallel Aerodynamics and Reentry Code) will provide nuclear weapon qualification evidence for the random vibration and thermal environments created by re-entry of a warhead into the earth’s atmosphere. SPARC incorporates the innovative approaches of ATDM projects on several fronts including: effective harnessing of heterogeneous compute nodes using Kokkos, exascale-ready parallel scalability through asynchronous multi-tasking, uncertainty quantification through Sacado integration, implementation of state-of-the-art reentry physics and multiscale models, use of advanced verification and validation methods, and enabling of improved workflows for users. SPARC is being developed primarily for the Department of Energy nuclear weapon program, with additional development and use of the code is being supported by the Department of Defense for conventional weapons programs.

Robinson, Allen C.; Petney, Sharon P.; Drake, Richard R.; Weirs, Vincent G.; Adams, Brian M.; Vigil, Dena V.; Carpenter, John H.; Garasi, Christopher J.; Wong, Michael K.; Robbins, Joshua R.; Siefert, Christopher S.; Strack, Otto E.; Wills, Ann E.; Trucano, Timothy G.; Bochev, Pavel B.; Summers, Randall M.; Stewart, James R.; Ober, Curtis C.; Rider, William J.; Haill, Thomas A.; Lemke, Raymond W.; Cochrane, Kyle C.; Desjarlais, Michael P.; Love, Edward L.; Voth, Thomas E.; Mosso, Stewart J.; Niederhaus, John H.

Abstract not provided.

46th AIAA Aerospace Sciences Meeting and Exhibit

Robinson, Allen C.; Brunner, Thomas A.; Carroll, Susan; Richarddrake; Garasi, Christopher J.; Gardiner, Thomas; Haill, Thomas; Hanshaw, Heath; Hensinger, David; Labreche, Duane; Lemke, Raymond; Love, Edward; Luchini, Christopher; Mosso, Stewart; Niederhaus, John; Ober, Curtis C.; Petney, Sharon; Rider, William J.; Scovazzi, Guglielmo; Strack, O.E.; Summers, Randall; Trucano, Timothy; Weirs, V.G.; Wong, Michael; Voth, Thomas

ALEGRA is an arbitrary Lagrangian-Eulerian (multiphysics) computer code developed at Sandia National Laboratories since 1990. The code contains a variety of physics options including magnetics, radiation, and multimaterial flow. The code has been developed for nearly two decades, but recent work has dramatically improved the code's accuracy and robustness. These improvements include techniques applied to the basic Lagrangian differencing, artificial viscosity and the remap step of the method including an important improvement in the basic conservation of energy in the scheme. We will discuss the various algorithmic improvements and their impact on the results for important applications. Included in these applications are magnetic implosions, ceramic fracture modeling, and electromagnetic launch. Copyright © 2008 by the American Institute of Aeronautics and Astronautics, Inc.

Love, Edward L.; Scovazzi, Guglielmo S.; Rider, William J.

Algorithmic properties of the midpoint predictor-corrector time integration algorithm are examined. In the case of a finite number of iterations, the errors in angular momentum conservation and incremental objectivity are controlled by the number of iterations performed. Exact angular momentum conservation and exact incremental objectivity are achieved in the limit of an infinite number of iterations. A complete stability and dispersion analysis of the linearized algorithm is detailed. The main observation is that stability depends critically on the number of iterations performed.

Carpenter, John H.; Robinson, Allen C.; Debusschere, Bert D.; Wills, Ann E.; Drake, Richard R.; Rider, William J.

Abstract not provided.

Love, Edward L.; Rider, William J.; Scovazzi, Guglielmo S.

Abstract not provided.

Love, Edward L.; Rider, William J.; Scovazzi, Guglielmo S.

Abstract not provided.

Wills, Ann E.; Rider, William J.

Abstract not provided.

Rider, William J.; Kamm, James R.

Abstract not provided.

Rider, William J.; Wills, Ann E.

Abstract not provided.

Weirs, Vincent G.; Rider, William J.; Kamm, James R.

Abstract not provided.

Hills, Richard G.; Witkowski, Walter R.; Rider, William J.; Trucano, Timothy G.; Urbina, Angel U.

The Predictive Capability Maturity Model (PCMM) is an expert elicitation tool designed to characterize and communicate completeness of the approaches used for computational model definition, verification, validation, and uncertainty quantification associated for an intended application. The primary application of this tool at Sandia National Laboratories (SNL) has been for physics-based computational simulations in support of nuclear weapons applications. The two main goals of a PCMM evaluation are 1) the communication of computational simulation capability, accurately and transparently, and 2) the development of input for effective planning. As a result of the increasing importance of computational simulation to SNLs mission, the PCMM has evolved through multiple generations with the goal to provide more clarity, rigor, and completeness in its application. This report describes the approach used to develop the fourth generation of the PCMM.

Rider, William J.; Weirs, Vincent G.; Love, Edward L.

Abstract not provided.

Robinson, Allen C.; Drake, Richard R.; Carpenter, John H.; Wills, Ann E.; Rider, William J.; Debusschere, Bert D.

Abstract not provided.

Gardiner, Thomas A.; Rider, William J.; Robinson, Allen C.

Abstract not provided.

Computers and Fluids

Robinson, Allen C.; Berry, Robert D.; Carpenter, John H.; Debusschere, Bert D.; Drake, Richard R.; Mattsson, A.E.; Rider, William J.

Uncertainty quantification (UQ) deals with providing reasonable estimates of the uncertainties associated with an engineering model and propagating them to final engineering quantities of interest. We present a conceptual UQ framework for the case of shock hydrodynamics with Euler's equations where the uncertainties are assumed to lie principally in the equation of state (EOS). In this paper we consider experimental data as providing both data and an estimate of data uncertainty. We propose a specific Bayesian inference approach for characterizing EOS uncertainty in thermodynamic phase space. We show how this approach provides a natural and efficient methodology for transferring data uncertainty to engineering outputs through an EOS representation that understands and deals consistently with parameter correlations as sensed in the data.Historically, complex multiphase EOSs have been built utilizing tables as the delivery mechanism in order to amortize the cost of creation of the tables over many subsequent continuum scale runs. Once UQ enters into the picture, however, the proper operational paradigm for multiphase tables become much less clear. Using a simple single-phase Mie-Grüneisen model we experiment with several approaches and demonstrate how uncertainty can be represented. We also show how the quality of the tabular representation is of key importance. As a first step, we demonstrate a particular tabular approach for the Mie-Grüneisen model which when extended to multiphase tables should have value for designing a UQ-enabled shock hydrodynamic modeling approach that is not only theoretically sound but also robust, useful, and acceptable to the modeling community. We also propose an approach to separate data uncertainty from modeling error in the EOS. © 2012 Elsevier Ltd.

Robinson, Allen C.; Carpenter, John H.; Drake, Richard R.; Wills, Ann E.; Rider, William J.; Berry, Robert D.; Debusschere, Bert D.

Abstract not provided.

Rider, William J.; Kelly, Suzanne M.; Barrett, Richard F.; Hammond, Simon D.

Abstract not provided.

Kelly, Suzanne M.; Rider, William J.; Barrett, Richard F.; Hammond, Simon D.

Abstract not provided.

Cyr, Eric C.; Shadid, John N.; Wildey, Timothy M.; Hensinger, David M.; Robinson, Allen C.; Rider, William J.; Scovazzi, Guglielmo S.

Abstract not provided.