James S. Peery

Multi-material ALE methods in unstructured grids

Arbitrary Lagrangian Eulerian (ALE) methods have existed for several decades. However, three-dimensional Multi-Material Arbitrary Lagrangian Eulerian (MMALE) methods for unstructured grids are relatively new. MMALE algorithms provide the framework to model sections of a simulation as either Lagrangian, ALE, or Eulerian. In addition, sections of a simulation can switch in time between mesh motions as the distortion of the problem dictates. The MMALE method provides the accuracy of Lagrangian mesh motion and the robustness of Eulerian mesh motion within the same framework. Extending this method to unstructured grids allows for more accurate representation of curved surfaces and complex geometries. This paper examines the algorithms required for the MMALE method and the extensions to these algorithms for unstructured meshes. In addition, second-order behavior of the MMALE algorithm as it exists in the high energy density physics code Arbitrary Lagrangian Eulerian General Research Applications code (ALEGRA) is demonstrated, along with a practical example of its usefulness.

Salinas: A Scalable Software for High-Performance Structural and Solid Mechanics Simulations

We present Salinas, a scalable implicit software application for the finite element static and dynamic analysis of complex structural real-world systems. This relatively complete engineering software with more than 100,000 lines of C++ code and a long list of users sustains 292.5 Gflop/s on 2,940 ASCI Red processors, and 1.16 Tflop/s on 3,375 ASCI White processors.

Recent progress in ALEGRA development and application to ballistic impacts

ALEGRA is a multi-material, arbitrary-Lagrangian-Eulerian (ALE) code for solid dynamics being developed by the Computational Physics Research and Development Department at Sandia National Laboratories. It combines the features of modem Eulerian shock codes, such as CTH, with modem Lagrangian structural analysis codes. With the ALE algorithm , the mesh can be stationary (Eulerian) with the material flowing through the mesh, the mesh ran move with the material (Lagrangian) so there is no flow between elements, or the mesh motion can be entirely independent of the material motion (Arbitrary). All three mesh types can coexist in the same problem and any mesh may change its type during the calculation. In this paper we summarize several key capabilities that have recently been added to the code or are currently being implemented. As a demonstration of the capabilities of ALEGRA, we have applied it to the experimental data taken by Silsby.

ALEGRA: User Input and Physics Descriptions Version 4.2

ALEGRA is an arbitrary Lagrangian-Eulerian finite element code that emphasizes large distortion and shock propagation. This document describes the user input language for the code.

Mechanism free domain decomposition

The simulation of three-dimensional (3D) structural dynamics on massively parallel platforms places stringent requirements on the existing software infrastructure. A constrained and nonlinear graph partitioning problem that arises in scalable iterative substructuring methods, such as finite element tearing and interconnecting (FETI) methods, is identified. New sufficient criteria on a partition are presented that ensure the applicability of FETI methods, and improve the associated preconditioner. One-dimensional finite elements in 3D structures are treated by an encapsulation method. The techniques are demonstrated on complex finite element model problems.

A methodology to validate 3D Arbitrary Lagrangian Eulerian codes with applications to ALEGRA

Abstract In this study we provided an experimental test bed for validating features of the Arbitrary Lagrangian Eulerian Grid for Research Applications (ALEGRA) code over a broad range of strain rates with overlapping diagnostics that encompass the multiple responses. A unique feature of the ALEGRA code is that it allows simultaneous computational treatment, within one code, of a wide range of strain-rates varying from hydrodynamic to structural conditions. This range encompasses strain rates characteristic of shock-wave propagation (10 7 /s) and those characteristics of structural response (10 2 /s). Most previous code validation experimental studies, however, have been restricted to simulating or investigating a single strain-rate regime. What is new and different in this investigation is that we have performed well-controlled and well-instrumented experiments, which capture features relevant to both hydrodynamic and structural response in a single experiment. Aluminum was chosen for use in this study because it is a well-characterized material. The current experiments span strain rate regimes of over 10 7 /s to less than 10 2 /s in a single experiment. The input conditions were extremely well defined. Velocity interferometers were used to record the high strain-rate response, while low strain rate data were collected using strain gauges. Although the current tests were conducted at a nominal velocity of ∼ 1.5 km/s, it is the test methodology that is being emphasized herein. Results of a three-dimensional experiment are also presented.

The development and application of massively parallel solid mechanics codes

Computational physicists at Sandia National Laboratories have moved the Eulerian CTH code, and the arbitrary-Lagrangian-Eulerian ALEGRA code to distributed memory parallel computers. CTH is a three-dimensional solid mechanics code used for large-deformation, shock wave analysis. ALEGRA is a three-dimensional arbitrary Lagrangian-Eulerian solid-mechanics code used for coupled large-deformation, shock and structural mechanics problems. This paper discusses our experiences moving the codes to parallel computers, the algorithms we used and our experiences running the codes.