Publications

Ebeida, Mohamed S.; Mitchell, Scott A.; Knupp, Patrick K.

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Knupp, Patrick K.; Day, David M.

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Knupp, Patrick K.

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Mitchell, Scott A.; Ebeida, Mohamed S.; Knupp, Patrick K.

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Knupp, Patrick K.

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Engineering with Computers

Knupp, Patrick K.

A general-purpose algorithm for mesh optimization via node-movement, known as the Target-Matrix Paradigm, is introduced. The algorithm is general purpose in that it can be applied to a wide variety of mesh and element types, and to various commonly recurring mesh optimization problems such as shape improvement, and to more unusual problems like boundary-layer preservation with sliver removal, high-order mesh improvement, and edge-length equalization. The algorithm can be considered to be a direct optimization method in which weights are automatically constructed to enable definitions of application- specific mesh quality. The high-level concepts of the paradigm have been implemented in the Mesquite mesh improvement library, along with a number of concrete algorithms that address mesh quality issues such as those shown in the examples of the present paper. © Springer-Verlag (outside the USA) 2011.

Ebeida, Mohamed S.; Knupp, Patrick K.

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Knupp, Patrick K.; Urbina, Angel U.

There is currently sparse literature on how to implement systematic and comprehensive processes for modern V&V/UQ (VU) within large computational simulation projects. Important design requirements have been identified in order to construct a viable 'system' of processes. Significant processes that are needed include discovery, accumulation, and assessment. A preliminary design is presented for a VU Discovery process that accounts for an important subset of the requirements. The design uses a hierarchical approach to set context and a series of place-holders that identify the evidence and artifacts that need to be created in order to tell the VU story and to perform assessments. The hierarchy incorporates VU elements from a Predictive Capability Maturity Model and uses questionnaires to define critical issues in VU. The place-holders organize VU data within a central repository that serves as the official VU record of the project. A review process ensures that those who will contribute to the record have agreed to provide the evidence identified by the Discovery process. VU expertise is an essential part of this process and ensures that the roadmap provided by the Discovery process is adequate. Both the requirements and the design were developed to support the Nuclear Energy Advanced Modeling and Simulation Waste project, which is developing a set of advanced codes for simulating the performance of nuclear waste storage sites. The Waste project served as an example to keep the design of the VU Discovery process grounded in practicalities. However, the system is represented abstractly so that it can be applied to other M&S projects.

Knupp, Patrick K.

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Ebeida, Mohamed S.; Mitchell, Scott A.; Knupp, Patrick K.; Leung, Vitus J.

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Ebeida, Mohamed S.; Knupp, Patrick K.; Mitchell, Scott A.; Leung, Vitus J.

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Ebeida, Mohamed S.; Knupp, Patrick K.; Leung, Vitus J.

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Mitchell, Scott A.; Knupp, Patrick K.; Ebeida, Mohamed S.

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Mitchell, Scott A.; Knupp, Patrick K.; Ebeida, Mohamed S.

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Edwards, Harold C.; Arguello, Jose G.; Bartlett, Roscoe B.; Bouchard, Julie F.; Freeze, Geoffrey A.; Knupp, Patrick K.; Schultz, Peter A.; Urbina, Angel U.; Wang, Yifeng

The objective of the U.S. Department of Energy Office of Nuclear Energy Advanced Modeling and Simulation Waste Integrated Performance and Safety Codes (NEAMS Waste IPSC) is to provide an integrated suite of computational modeling and simulation (M&S) capabilities to quantitatively assess the long-term performance of waste forms in the engineered and geologic environments of a radioactive-waste storage facility or disposal repository. To meet this objective, NEAMS Waste IPSC M&S capabilities will be applied to challenging spatial domains, temporal domains, multiphysics couplings, and multiscale couplings. A strategic verification and validation (V&V) goal is to establish evidence-based metrics for the level of confidence in M&S codes and capabilities. Because it is economically impractical to apply the maximum V&V rigor to each and every M&S capability, M&S capabilities will be ranked for their impact on the performance assessments of various components of the repository systems. Those M&S capabilities with greater impact will require a greater level of confidence and a correspondingly greater investment in V&V. This report includes five major components: (1) a background summary of the NEAMS Waste IPSC to emphasize M&S challenges; (2) the conceptual foundation for verification, validation, and confidence assessment of NEAMS Waste IPSC M&S capabilities; (3) specifications for the planned verification, validation, and confidence-assessment practices; (4) specifications for the planned evidence information management system; and (5) a path forward for the incremental implementation of this V&V plan.

Swiler, Laura P.; Knupp, Patrick K.

Predictive Capability Maturity Model (PCMM) is a communication tool that must include a dicussion of the supporting evidence. PCMM is a tool for managing risk in the use of modeling and simulation. PCMM is in the service of organizing evidence to help tell the modeling and simulation (M&S) story. PCMM table describes what activities within each element are undertaken at each of the levels of maturity. Target levels of maturity can be established based on the intended application. The assessment is to inform what level has been achieved compared to the desired level, to help prioritize the VU activities & to allocate resources.

Devine, Karen D.; Copps, Kevin D.; Ebeida, Mohamed S.; Hensinger, David M.; Knupp, Patrick K.; Sjaardema, Gregory D.; Williams, Alan B.

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Knupp, Patrick K.

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Knupp, Patrick K.

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Knupp, Patrick K.

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Knupp, Patrick K.

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Knupp, Patrick K.

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46th AIAA Aerospace Sciences Meeting and Exhibit

Knupp, Patrick K.

Various aspects of mesh quality are surveyed to clarify the disconnect between the traditional uses of mesh quality metrics within industry and the fact that quality ultimately depends on the solution to the physical problem. Truncation error analysis for ffnite difference methods reveals no clear connection to most traditional mesh quality metrics. Finite element bounds to the interpolation error can be shown, in some cases, to be related to known quality metrics such as the condition number. On the other hand, the use of quality metrics that do not take solution characteristics into account can be valid in certain circumstances, primarily as a means of automatically detecting defective meshes. The use of such metrics when applied to simulations for which quality is highly-dependent on the physical solution is clearly inappropriate. Various ffaws and problems with existing quality metrics are mentioned, along with a discussion on the use of threshold values. In closing, the author advocates the investigation of explicitly-referenced quality metrics as a potential means of bridging the gap between a priori quality metrics and solution-dependent metrics.

Proceedings of the 16th International Meshing Roundtable, IMR 2007

Pébay, Philippe P.; Thompson, David; Shepherd, Jason F.; Knupp, Patrick K.; Lisle, Curtis; Magnotta, Vincent A.; Grosland, Nicole M.

Verdict is a collection of subroutines for evaluating the geometric qualities of triangles, quadrilaterals, tetrahedra, and hexahedra using a variety of functions. A quality is a real number assigned to one of these shapes depending on its particular vertex coordinates. These functions are used to evaluate the input to finite element, finite volume, boundary element, and other types of solvers that approximate the solution to partial differential equations defined over regions of space. This article describes the most recent version of Verdict and provides a summary of the main properties of the quality functions offered by the library. It finally demonstrates the versatility and applicability of Verdict by illustrating its use in several scientific applications that pertain to pre, post, and end-to-end processing.

Knupp, Patrick K.

Abstract not provided.