Research in progress in applied mathematics, numerical analysis, fluid mechanics, and computer science

This report summarizes research conducted at the Institute for Computer Applications in Science and Engineering in applied mathematics, fluid mechanics, and computer science during the period October 1, 1993 through March 31, 1994. The major categories of the current ICASE research program are: (1) applied and numerical mathematics, including numerical analysis and algorithm development; (2) theoretical and computational research in fluid mechanics in selected areas of interest to LaRC, including acoustics and combustion; (3) experimental research in transition and turbulence and aerodynamics involving LaRC facilities and scientists; and (4) computer science

[Activity of Institute for Computer Applications in Science and Engineering]

This report summarizes research conducted at the Institute for Computer Applications in Science and Engineering in applied mathematics, fluid mechanics, and computer science

Semiannual report

This report summarizes research conducted at the Institute for Computer Applications in Science and Engineering in applied mathematics, fluid mechanics, and computer science during the period 1 Oct. 1994 - 31 Mar. 1995

[Research activities in applied mathematics, fluid mechanics, and computer science]

This report summarizes research conducted at the Institute for Computer Applications in Science and Engineering in applied mathematics, fluid mechanics, and computer science during the period April 1, 1995 through September 30, 1995

Research in applied mathematics, numerical analysis, and computer science

Research conducted at the Institute for Computer Applications in Science and Engineering (ICASE) in applied mathematics, numerical analysis, and computer science is summarized and abstracts of published reports are presented. The major categories of the ICASE research program are: (1) numerical methods, with particular emphasis on the development and analysis of basic numerical algorithms; (2) control and parameter identification; (3) computational problems in engineering and the physical sciences, particularly fluid dynamics, acoustics, and structural analysis; and (4) computer systems and software, especially vector and parallel computers

Calcul haute performance pour la simulation d'interactions fluide-structure

Cette thèse aborde la résolution des problèmes d'interaction fluide-structure par un algorithme consistant en un couplage entre deux solveurs : un pour le fluide et un pour la structure. Pour assurer la cohérence entre les maillages fluide et structure, on considère également une discrétisation de chaque domaine par volumes finis. En raison des difficultés de décomposition du domaine en sous-domaines, nous considérons pour chaque environnement un algorithme parallèle de multi-splitting (ou multi-décomposition) qui correspond à une présentation unifiée des méthodes de sous-domaines avec ou sans recouvrement. Cette méthode combine plusieurs applications de points fixes contractantes et nous montrons que, sous des hypothèses appropriées, chaque application de points fixes est contractante dans des espaces de dimensions finies normés par des normes hilbertiennes et non-hilbertiennes. De plus, nous montrons qu'une telle étude est valable pour les résolutions parallèles synchrones et plus généralement asynchrones de grands systèmes linéaires apparaissant lors de la discrétisation des problèmes d'interaction fluide-structure et peut être étendue au cas où le déplacement de la structure est soumis à des contraintes. Par ailleurs, nous pouvons également considérer l’analyse de la convergence de ces méthodes de multi-splitting parallèles asynchrones par des techniques d’ordre partiel, lié au principe du maximum discret, aussi bien dans le cadre linéaire que dans celui obtenu lorsque les déplacements de la structure sont soumis à des contraintes. Nous réalisons des simulations parallèles pour divers cas test fluide-structure sur différents clusters, en considérant des communications bloquantes et non bloquantes. Dans ce dernier cas nous avons eu à résoudre une difficulté d'implémentation dans la mesure où une erreur irrécupérable survenait lors de l'exécution ; cette difficulté a été levée par introduction d’une méthode assurant la terminaison de toutes les communications non bloquantes avant la mise à jour du maillage. Les performances des simulations parallèles sont présentées et analysées. Enfin, nous appliquons la méthodologie présentée précédemment à divers contextes d'interaction fluide-structure de type industriel sur des maillages non structurés, ce qui constitue une difficulté supplémentaire

Department of Computer Science Activity 1998-2004

This report summarizes much of the research and teaching activity of the Department of Computer Science at Dartmouth College between late 1998 and late 2004. The material for this report was collected as part of the final report for NSF Institutional Infrastructure award EIA-9802068, which funded equipment and technical staff during that six-year period. This equipment and staff supported essentially all of the department\u27s research activity during that period

A Unifying Theory for Nonlinear Additively and Multiplicatively Preconditioned Globalization Strategies : Convergence Results and Examples From the Field of Nonlinear Elastostatics and Elastodynamics

Nonlinear right preconditioned globalization strategies for the solution of nonlinear programming problems of the following kind $u \in \mathcal B \subset \mathbb R^n: J(u) = \min!$ where $\mathcal B$ is a convex set of admissible solutions, $n\in \mathbb N$, and $J: \mathbb R^n \to \mathbb R$, sufficiently smooth, are presented. Preconditioned globalization strategies are traditional Linesearch or Trust-Region strategies in combination with a nonlinear update operator which results from a nonlinear solution process for smaller, but related, nonlinear programming problems. We will formulate conditions on this abstract operator, in order to ensure global convergence, i.e., convergence to first-order critical points, of the resulting method. In addition, we introduce particular implementations of this abstract operator, i.e., nonlinear multiplicatively preconditioned Trust-Region (MPTS) and Linesearch strategies (MPLS), as well as nonlinear additively preconditioned Trust-Region (APTS) and Linesearch (APLS) strategies. As it turns out, these additive strategies are novel parallel, locally adaptive and robust solution methods for nonlinear programming problems. Moreover, the MPTS strategy generalizes the RMTR concepts in [GK08] in order to allow also for the application of alternating nonlinear domain decomposition methods. On the other hand, the MPLS method simplifies and generalizes the concepts in [WG08] giving rise to a novel solution strategy for pointwise constrained nonlinear programming problems. The respective nonlinear solution strategies are analyzed and global convergence is shown. In addition, global convergence is also shown for combined nonlinear additively and multiplicatively preconditioned Trust-Region and Linesearch strategies. Moreover, we show the efficiency and reliability of these methods in the context of problems arising from the field of nonlinear elasticity in 3d. Particular emphasis has been placed on the formulation and analysis of the resulting minimization problems. Here, we show that these problems satisfy the assumptions stated to show convergence of the respective preconditioned globalization strategies. Moreover, various elasto-static and elasto-dynamic examples are presented in order to compare the convergence rates and runtimes of the different strategies

ICASE

This report summarizes research conducted at the Institute for Computer Applications in Science and Engineering in the areas of (1) applied and numerical mathematics, including numerical analysis and algorithm development; (2) theoretical and computational research in fluid mechanics in selected areas of interest, including acoustics and combustion; (3) experimental research in transition and turbulence and aerodynamics involving Langley facilities and scientists; and (4) computer science