Kendall H. Pierson

A scalable dual-primal domain decomposition method

We blend dual and primal domain decomposition approaches to construct a fast iterative method for the solution of large-scale systems of equations arising from the finite element discretization of second- and fourth-order partial differential equations. We show numerically that our method is scalable with respect to the mesh size, the subdomain size, and the number of elements per subdomain. We apply it to the solution of several realistic structural mechanics problems, and report on parallel performance results obtained on an Origin 2000 system, as well as the ASCI Option Red supercomputer. Copyright

The second generation FETI methods and their application to the parallel solution of large-scale linear and geometrically non-linear structural analysis problems

The FETI algorithms are a family of numerically scalable domain decomposition methods. They have been designed in the early 1990s for solving iteratively and on parallel machines, large-scale systems of equations arising from the finite element discretization of solid mechanics, structural engineering, structural dynamics, and acoustic scattering problems, and for analyzing complex structures obtained from the assembly of substructures with incompatible discrete interfaces. In this paper, we present the second generation of these methods that operate more efficiently on large numbers of subdomains, offer greater robustness, better performance, and more flexibility for implementation on a wider variety of computational platforms. We also report on the application and performance of these methods for the solution of geometrically non-linear structural analysis problems. We discuss key aspects of their implementation on shared and distributed memory parallel processors, benchmark them against optimized direct sparse solvers, and highlight their potential with the solution of large-scale structural mechanics problems with several million degrees of freedom.

Application of the FETI method to ASCI problems—scalability results on 1000 processors and discussion of highly heterogeneous problems

We report on the application of the one-level FETI method to the solution of a class of structural problems associated with the Department of Energys Accelerated Strategic Computing Initiative (ASCI). We focus on numerical and parallel scalability issues,and discuss the treatment by FETI of severe structural heterogeneities. We also report on preliminary performance results obtained on the ASCI Option Red supercomputer configured with as many as one thousand processors, for problems with as many as 5 million degrees of freedom.

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.

Multidisciplinary Simulation of the Maneuvering of an Aircraft

A computational methodology for the simulation of the transient aeroelastic response of an unrestrained and flexible aircraft during high-G maneuvers is presented. The key components of this methodology are: (a) a three-field formulation for coupled fluid/structure interaction problems; (b) a second-order time-accurate and geometrically conservative flow solver for CFD computations on unstructured dynamic meshes; (c) a corotational finite element method for the solution of geometrically nonlinear and unrestrained structural dynamics problems; (d) a robust method for updating an unrestrained and unstructured moving fluid mesh; and (e) a second-order time-accurate staggered algorithm for time-integrating the coupled fluid/structure semi-discrete equations of motion. This computational methodology is illustrated with the simulation on a parallel processor of several three-dimensional high-G pullup maneuvers of the Langley Fighter in the transonic regime, using a detailed finite element aeroelastic model.

Experiences with FETI-DP in a Production Level Finite Element Application

We discuss application of the FETI-DP linear solver within the Salinas finite element application. An overview of Salinas and of the FETI-DP solver is presented. We discuss scalability of the software on ASCI-red, Cplant and ASCI-white. Options for solution of the coarse grid problem that results from the FETI problem are evaluated. The finite element software and solver are seen to be numerically and cpu scalable on each of these platforms. In addition, the software is very robust and can be used on a large variety of finite element models.

Peridynamic Simulation of Damage Evolution for Structural Health Monitoring.

Modal-based methods for structural health monitoring require the identification of characteristic frequencies associated with a structure’s primary modes of failure. A major difficulty is the extraction of damage-related frequency shifts from the large set of often benign frequency shifts observed experimentally. In this study, we apply peridynamics in combination with modal analysis for the prediction of characteristic frequency shifts throughout the damage evolution process. Peridynamics, a nonlocal extension of continuum mechanics, is unique in its ability to capture progressive material damage. The application of modal analysis to peridynamic models enables the tracking of structural modes and characteristic frequencies over the course of a simulation. Shifts in characteristic frequencies resulting from evolving structural damage can then be isolated and utilized in the analysis of frequency responses observed experimentally. We present a methodology for quasi-static peridynamic analyses, including the solution of the eigenvalue problem for identification of structural modes. Repeated solution of the eigenvalue problem over the course of a transient simulation yields a data set from which critical shifts in modal frequencies can be isolated. The application of peridynamics to modal analysis is demonstrated on the benchmark problem of a simply-supported beam. The computed natural frequencies of an undamaged beam are found to agree well with the classical local solution. Analyses in the presence of cracks of various lengths are shown to reveal frequency shifts associated with structural damage.Copyright

Application of the FETI Method to ASCI Problems: Scalability Results on One Thousand Processors and Discussion of Highly Heterogeneous Problems

We report on the application of the one-level FETI method to the solution of a class of substructural problems associated with the Department of Energys Accelerated Strategic Computing Initiative (ASCI). We focus on numerical and parallel scalability issues, and on preliminary performance results obtained on the ASCI Option Red supercomputer configured with as many as one thousand processors, for problems with as many as 5 million degrees of freedom.

Adagio 4.20 User’s Guide

Adagio is a Lagrangian, three-dimensional, implicit code for the analysis of solids and structures. It uses a multi-level iterative solver, which enables it to solve problems with large deformations, nonlinear material behavior, and contact. It also has a versatile library of continuum and structural elements, and an extensive library of material models. Adagio is written for parallel computing environments, and its solvers allow for scalable solutions of very large problems. Adagio uses the SIERRA Framework, which allows for coupling with other SIERRA mechanics codes. This document describes the functionality and input structure for Adagio.

Computational and experimental techniques for coupled acoustic/structure interactions.

This report documents the results obtained during a one-year Laboratory Directed Research and Development (LDRD) initiative aimed at investigating coupled structural acoustic interactions by means of algorithm development and experiment. Finite element acoustic formulations have been developed based on fluid velocity potential and fluid displacement. Domain decomposition and diagonal scaling preconditioners were investigated for parallel implementation. A formulation that includes fluid viscosity and that can simulate both pressure and shear waves in fluid was developed. An acoustic wave tube was built, tested, and shown to be an effective means of testing acoustic loading on simple test structures. The tube is capable of creating a semi-infinite acoustic field due to nonreflecting acoustic termination at one end. In addition, a micro-torsional disk was created and tested for the purposes of investigating acoustic shear wave damping in microstructures, and the slip boundary conditions that occur along the wet interface when the Knudsen number becomes sufficiently large.