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12th computational Fluid Dynamics Conference, 1995

作者： Marcum, David L. Weatherill, Nigel P. Merchant, Michael J. Beaven, Frank NSF Engineering Research Center for Computational Field Simulation Mechanical Engineering Department Mississippi State University United States Department of Civil Engineering University of Wales Swansea United Kingdom

A procedure is presented for efficient generation of high-quality solution-adapted grids suitable for viscous flow applications. The overall procedure is based on an existing grid generation method which uses advancing front/advancing-nod point placement with direct insertion and iterative local-reconnection. With this method, high-quality unstructured grids can be efficiently generated about geometrically complex configurations with field point spacing derived from the boundaries. The procedure is modified to allow the field point spacing to vary based on a flow field solution using adaptive grid regeneration. Inviscid type features, such as shock waves and stagnation points, are resolved using iterative adaptation sources derived from the flow field solution. Detached viscous features, such as wakes, are resolved by tracking selected streamlines and treating them as boundary surfaces with a specified spacing. Results are presented for two-dimensional cases with multiple viscous wakes and strong inviscid features. Preliminary results are also presented for extension of this methodology to three-dimensions using stream surface tracking. The results indicate that high-quality solution-adapted unstructured grids suitable for viscous flow applications can be generated efficiently. © 1995 American Institute of Aeronautics and Astronautics, Inc. All rights reserved.

关键词： Viscous flow

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computational analysis of compensated pitot-static probes using the euler equations 13th

Computational analysis of compensated pitot-static probes us...

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13th Applied Aerodynamics Conference, 1995

作者： Swafford, T.W. Bomba, J. Daiber, M.P. Engineering Research Center for Computational Field Simulation NSF Engineering Research Center Mississippi State University P.O. Box 6176 MS39762 United States Aero Instrument Company Inc 14901 Emery Ave ClevelandOH44135 United States

ISBN: (纸本)9781563471230

Both static and total (stagnation) pressure measurement devices are required to infer airspeed and altitude information necessary for an aircraft’s primary navigation. Compensated Pitot-static tubes combine both pressure sensors on one device, and are currently in use on many aircraft. However, each probe design and/or probe location must necessarily be different because of the varied flow fields generated by different forebody topologies. A priori knowledge of these flow fields obtained through the use of computational fluid dynamics (CFD) can compress development time and reduce unit cost by limiting wind tunnel and flight testing experiments associated with trial-and-error probe design procedures. It is the objective of this paper to describe efforts aimed at development and adaptation of computational analysis tools tailored specifically for the design of Pitot-stat-ic tube configurations. It is demonstrated that simplified axisymmetric calculations can be used to guide the early stages of the probe design process. The design that emerges from these calculations is then evaluated using corresponding three-dimensional computations about a typical business aircraft forebody which includes the probe as part of the geometry. Based on the results presented, it is concluded that computational procedures can be used effectively as a design tool, but unfortunately remain too expensive to be considered for use on hardware platforms other than state-of-the-art engineering workstations. © 1995 by the American Institute of Aeronautics and Astronautics, Inc. All rights reserved.

关键词： Probes

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Migrating from PVM to MPI.I. The Unify system

Migrating from PVM to MPI.I. The Unify system

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Frontiers of Massively Parallel Computation

作者： P.L. Vaughan A. Skjellum D.S. Reese Fei-Chen Cheng NSF Engineering Research Center for Computational Field Simulation Mississippi State University MS USA Department of Computer Science Mississippi State University MS USA

This paper presents a new kind of portability system, Unify, which modifies the PVM message passing system to provide (currently a subset of) the message Passing Interface (MPI) standard notation for message passing. Unify is designed to reduce the effort of learning MPI, while providing a sensible means to make use of MPI libraries and MPI calls (while applications continue to run in the PVM environment). We are convinced that this strategy will reduce the costs of porting completely to MPI, while providing a gradual environment within which to evolve. Furthermore, it will permit immediate use of MPI-based parallel libraries in applications, even for those applications that continue to use PVM for message passing. We describe several paradigms for supporting MPI and PVM message passing notations in a single environment, and note related work on MPI and PVM implementations. We show the design options that existed within our chosen paradigm (which is an MPI interface added to the base PVM system) and why we chose that particular approach. We indicate the total evolution path of porting a PVM application to MPI with the help of porting libraries. Finally, we indicate our current directions and planned future work.< >

关键词： Message passing Computer interfaces computational modeling Libraries Computer simulation Costs Code standards Software standards Software tools Acceleration

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SURFACE GRID GENERATION BASED ON ELLIPTIC PDE MODELS

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APPLIED MATHEMATICS AND COMPUTATION 1994年第1-3期65卷 253-264页

作者： KHAMAYSEH, A MASTIN, CW NSF Engineering Research Center for Computational Field Simulation Mississippi State University Mississippi State Mississippi 39762 USA Department of Mathematics and Statistics/NSF Engineering Research Center for Computational Field Simulation Mississippi State University Mississippi State Mississippi 39762 USA

Elliptic grid generation methods for the construction of surface grids are discussed. An improved elliptic surface grid generation method for parametric surfaces will be presented. Two methods of imposing grid orthogonality have been implemented. Several control function options are available for maintaining a desired distribution of grid points on the surface. The overall effect of these improvements is a reliable and versatile elliptic method for generating and improving surface grids. Examples will be presented to demonstrate the application of the method in generating practical grids.

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FLUX-DIFFERENCE SPLITTINGS AND LIMITERS FOR THE RESOLUTION OF CONTACT DISCONTINUITIES

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APPLIED MATHEMATICS AND COMPUTATION 1994年第1-3期65卷 3-18页

作者： DAVIS, SF Department of Mathematics and Statistics NSF Engineering Research Center for Computational Field Simulation Mississippi State University Mississippi State Mississippi 39762 USA

Harten, Lax, and van Leer developed a theory of approximate Riemann solutions and used it to derive numerical methods for systems of conservation laws. In the first part of this paper, we reformulate this theory so that it can be used to compare various flux difference splitting formulae. In particular we show how to compare the resolution of contact discontinuities by various methods with that of the Roe method. Since the Roe method can resolve an isolated steady contact perfectly, it is a good standard for comparison. In the second part of the paper, we show that Harten's subcell resolution method is the ultimate compressive limiter. We discuss the differences between compressive and noncompressive limiters and show why it is important to choose the limiter to suit the problem at hand.

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Lossless progressive transmission of scientific data using biorthogonal wavelet transform

Lossless progressive transmission of scientific data using b...

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The 1994 1st IEEE International Conference on Image Processing

作者： Tao, Hai Moorhead, R.J. NSF Engineering Research Center for Computational Field Simulation Mississippi State University P.O. Box 6176 Mississippi StateMS39762 United States

A new progressive transmission scheme using spline biorthogonal wavelet bases is proposed in this paper. First, several wavelet bases are compared with the spline biorthogonal wavelet bases. By exploiting the properties of this set of wavelet bases, a fast algorithm involving only additions and subtractions is developed. Due to the multiresolutional nature of the wavelet transform, this scheme is compatible with hierarchical-structured rendering algorithms. The formula for reconstructing the functional values in a continuous volume space is given in a simple polynomial form. Lossless compression is possible, even when using floating-point numbers. When the algorithm is applied to data from a global ocean model, the lossless compression ratio is about 1.5:1. Even with a compression ratio of 50:1, the reconstructed data is still of good quality. Finally, the reconstructed data is rendered using various visualization algorithms and the results are demonstrated. © 1994 IEEE.

关键词： Digital arithmetic

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Exploring feature detection techniques for time-varying volumetric data

Exploring feature detection techniques for time-varying volu...

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IEEE Workshop on Visualization and Machine Vision

作者： Zhifan Zhu R.J. Moorhead NSF Engineering Research Center for Computational Field Simulation MS USA

ISBN: (纸本)0818658754

The fundamental purpose of scientific visualization is to help scientists extract information from large volumetric datasets. These multi-dimensional datasets may be either derived from observations or generated by simulations. In either case, visualization directly enhances scientific discovery, assists the validation and verification of simulation models, and helps study and predict phenomena. Although the state-of-the-art visualization techniques allow insightful presentations of datasets in various ways, the ability to discern significant features from complex data is lacking. On the other hand, lots of work has been done in the computer vision field, in attempting to automatically detect and recognize features or regions of interest in two-dimensional image data. How to extract features or locate regions of interest in visualizing high-dimensional datasets is an important area of research. We present the work we have done in exploring feature extraction techniques for time-varying three-dimensional volumetric datasets. We used an edge detection method and exploited both temporal and spatial coherences inside features to automatically locate and track the feature movement over time. The results are attractive and show that feature extraction techniques could greatly enhance visualization procedures.< >

关键词： Computer vision Data visualization Feature extraction Data mining Predictive models computational modeling Image recognition Image edge detection Spatial coherence Tracking

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Near-critical path analysis of program activity graphs

Near-critical path analysis of program activity graphs

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International Symposium on Modeling, Analysis and simulation of Computer and Telecommunication Systems (MASCOTS)

作者： C. Alexander D. Reese J. Harden NSF Engineering Research Center for Computational Field Simulation Mississippi State University USA

Program activity graphs can be constructed from time-stamped traces of appropriate execution events. Information about the activities on the k longest execution paths is useful in the analysis of parallel program performance. In this paper, four algorithms for finding the near-critical paths of program activity graphs are presented and compared, including an efficient new algorithm that utilizes slack values calculated by the critical path method to perform a best-first search in linear space. The worst-case time and memory requirements of the new algorithm are in O(ke) and O(k+e), where e is the number of edges in the graph. Results confirming the efficiency of the algorithm are presented for five application programs. A framework for utilizing the near-critical path information is also described. The framework includes both statistical summaries and visualization capabilities.< >

关键词： Performance analysis Probes Data visualization Concurrent computing computational modeling Analytical models Discrete event simulation Instruments Operating systems Multiprocessor interconnection networks

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Visualization of mesoscale flow features in ocean basins

Visualization of mesoscale flow features in ocean basins

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IEEE Conference on Visualization

作者： A. Johannsen R. Moorhead NSF Engineering Research Center for Computational Field Simulation Mississippi State University MS USA

Environmental issues such as global warming are an active area of international research and concern today. This case study describes various visualization paradigms that have been developed and applied in an attempt to elucidate the information provided by environmental models and observations. The ultimate goal is to accurately measure the existence of any long term climatological change. The global ocean is the starting point, since it is a major source and sink of heat within our global environment.< >

关键词： Data visualization Ocean temperature computational modeling Physics computing Acoustic propagation Global warming Solid modeling Acoustic signal detection Acoustic measurements Sea measurements

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Progressive transmission of scientific data using biorthogonal wavelet transform 94

Progressive transmission of scientific data using biorthogon...

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IEEE Conference on Visualization

作者： Hai Tao R.J. Moorhead NSF Engineering Research Center for Computational Field Simulation Mississippi State University MS USA

ISBN: (纸本)9780780325210

An important issue in scientific visualization systems is the management of data sets. Most data sets in scientific visualization, whether created by measurement or simulation, are usually voluminous. The goal of data management is to reduce the storage space and the access time of these data sets to speed up the visualization process. A new progressive transmission scheme using spline biorthogonal wavelet bases is proposed in this paper. By exploiting the properties of this set of wavelet bases, a fast algorithm involving only additions and subtractions is developed. Due to the multiresolutional nature of the wavelet transform, this scheme is compatible with hierarchical-structured rendering algorithms. The formula for reconstructing the functional values in a continuous volume space is given in a simple polynomial form. Lossless compression is possible, even when using floating-point numbers. This algorithm has been applied to data from a global ocean model. The lossless compression ratio is about 1.5:1. With a compression ratio of 50:1, the reconstructed data is still of good quality. Several other wavelet bases are compared with the spline biorthogonal wavelet bases. Finally the reconstructed data is visualized using various algorithms and the results are demonstrated.< >

关键词： Wavelet transforms Data visualization Continuous wavelet transforms Spline Polynomials Discrete cosine transforms Discrete wavelet transforms Decoding Filters computational modeling

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