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16th AIAA Applied Aerodynamics Conference, 1998

作者： Mavriplis, D.J. Institute for Computer Applications in Science and Engineering MS 403 NASA Langley Research Center HamptonVA23681-0001 United States

A directional implicit unstructured agglomeration multigrid solver is ported to shared and distributed memory massively parallel machines using the explicit domain-decomposition and message-passing approach. Because the algorithm operates on local implicit lines in the unstructured mesh, special care is required in partitioning the problem for parallel computing. A weighted partitioning strategy is described which avoids breaking the implicit lines across processor boundaries, while incurring minimal additional communication overhead. Good sealability is demonstrated on a 128 processor SGI Origin 2000 machine and on a 512 processor CRAY T3E machine for reasonably fine grids. The feasibility of performing large-scale unstructured grid calculations with the parallel multigrid algorithm is demonstrated by computing the flow over a partialspan flap wing high-lift geometry on a highly resolved grid of 13.5 million points in approximately 4 hours of wall clock time on the CRAY T3E. © 1998 by the American Institute of Aeronautics and Astronautics, Inc. All rights reserved.

关键词： Message passing

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Effect of finite computational domain on turbulence scaling law in both physical and spectral spaces

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Physical Review E 1998年第5期58卷 5841-5841页

作者： Thomas Y. Hou Xiao-Hui Wu Shiyi Chen Ye Zhou Institute for Computer Applications in Science and Engineering NASA Langley Research Center Hampton Virginia 23681

The well-known translation between the power law of the energy spectrum and that of the correlation function or the second order structure function has been widely used in analyzing random data. Here, we show that the translation is valid only in proper scaling regimes. The regimes of valid translation are different for the correlation function and the structure function. Indeed, they do not overlap. Furthermore, in practice, the power laws exist only for a finite range of scales. We show that this finite range makes the translation inexact even in the proper scaling regime. The error depends on the scaling exponent. The current findings are applicable to data analysis in fluid turbulence and other stochastic systems.

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Automated optimal design of two dimensional high speed missile inlets 36th

Automated optimal design of two dimensional high speed missi...

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36th AIAA aerospace sciences Meeting and Exhibit, 1998

作者： Blaize, Michael Knight, Doyle Rasheed, Khaled Department of Mechanical and Aerospace Engineering United States Department of Computer Science Center for Computational Design United States Rutgers University The State University of New Jersey PO Box 909 PiscatawayNJ08855-0909 United States

A new methodology has been developed for automated optimal design of two dimensional high speed inlets. A semi-empirical flow solver and an improved Genetic Algorithm are linked within an automated loop. The purpose of this process is to maximize the total pressure recovery of the missile inlet: first of all, for one upstream flow condition, and secondly for an entire mission. This innovative design strategy allows great improvement of the original inlet design in a very short period of time. Successful results are presented from optimizations of inlets designed and tested at the Institute of Theoretical and Applied Mechanics (ITAM) in Novosibirsk, Russia. The significant improvements of the total pressure recovery, achieved by the Automated Optimization Loop, are verified using a full Navier- Stokes solver. © 1997, American Institute of Aeronautics and Astronautics, Inc.

关键词： Missiles

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3-D hypersonic inlet optimization using a genetic algorithm 34th

3-D hypersonic inlet optimization using a genetic algorithm

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34th AIAA/ASME/SAE/ASEE Joint Propulsion Conference and Exhibit, 1998

作者： Chernyavsky, B. Stepanov, V. Rasheed, K. Blaize, M. Knight, D. Gas Dynamics Department of Central Institute of Aviation Motors Dept. Mechanical and Aerospace Engineering Rutgers University Moscow Central Institute of Aviation Motors Russia Rutgers University Dept. of Computer Science and Center for Computational Design New Brunswick Rutgers University NJ United States Dept. of Mechanical and Aerospace Engineering Center for Computational Design New Brunswick Rutgers University NJ United States

A numerical code has been developed for automatic aerodynamic optimization of supersonic 3- D inlet design with a high value of total pressure recovery coefficient with the aid of an improved Genetic Algorithm (GADO). The code combines GA and simple 1-D flow solver to form an optimization loop. The code is intended for optimization of inlet geometry, based on one optimization criteria and set of variable optimizing parameters. The code has been tested on a model problem considering optimization of Trexler-type 3-D inlet for Mach number range from 3 to 8. The optimizing parameters have been wedge panel angles and wedge leading edge sweep angle, determining inlet geometry. Total pressure recovery was used as an optimization criteria. The dependencies of wedge panel angles, wedge leading edge sweep angle and Mach number on total pressure recovery coefficient have been studied. Optimum inlet configurations have been obtained and compared for different number of wedge panels and Mach numbers in a range from 3 to 8. The influence of the turbulent boundary layer separation restriction on the integral inlet characteristics has been studied and obtained results have been compared for cases both with and without account for flow separation criteria. Calculations have shown, that account for turbulent boundary layer separation with the use of Gedd criterion significantly decrease expected inlet performance. © 1998 by Boris Chernyavsky, Vladimir Stepanov, Khaled Rasheed, Michael Blaize and Doyle Knight.

关键词： Mach number

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Getting the full benefits of CFD in conceptual design 16th

Getting the full benefits of CFD in conceptual design

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16th AIAA Applied Aerodynamics Conference, 1998

作者： Mason, William H. Knill, Duane L. Giunta, Anthony A. Grossman, Bernard Watson, Layne T. Haftka, Raphael T. Center for Advanced Vehicles Virginia Polytechnic Institute and State University BlacksburgVA24061 United States Dept. of Aerospace and Ocean Engineering Virginia Tech BlacksburgVA24061-0203 United States Dept. of Aeronautics and Astronautics University of Washington SeattleWA United States National Research Council NASA Langley Research Center HamptonVA United States Dept. of Aerospace and Ocean Engineering Virginia Tech United States Computer Science and Mathematics Virginia Tech BlacksburgVA24061-0203 United States Dept. of Aerospace Engineering Mechanics and Engineering Science Univ. of Florida GainesvilleFL32611-6250 United States Mechanics and Engineering Science University of Florida GainesvilleFL32611 United States

The applied aerodynamics community is struggling to develop a means of incorporating computational fluid dynamics (CFD) into the early stages of aircraft systems design, where it can have the greatest impact on vehicle design. This paper describes developments in computational design methodology arising from research into multidisciplinary design optimization (MDO) done recently by the authors that addresses this problem. The premise is that advanced CFD should be used to precompute a database of solutions which is then interpolated during the design process. Design of experiments theory is used to select the "conditions" or "design points" used to populate the database, and statistical methods are then used to develop a mathematical model of the CFD solutions which is used to "interpolate" the database. The specific models we use, called "response surface models" are quadratic least squares fits to functions of the CFD results. Populating the database is made possible through the use of coarse grained parallel computing. We demonstrate the method using a recent example from our MDO work. © 1998 by W.H. Mason. 1998 by W.H. Mason. Published by the American Institute of Aeronautics and Astronautics, Inc.

关键词： Computational fluid dynamics

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Energy spectra of strongly stratified and rotating turbulence

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Physical Review E 1998年第5期57卷 6187-6187页

作者： Alex Mahalov Basil Nicolaenko Ye Zhou Department of Mathematics Arizona State University Tempe Arizona 85287 IBM Research Division T.J. Watson Research Center P.O. Box 218 Yorktown Heights New York 10598 Institute for Computer Applications in Science and Engineering NASA Langley Research Center Hampton Virginia 23681

Turbulence under strong stratification and rotation is usually characterized as quasi-two-dimensional turbulence. We develop a “quasi-two-dimensional” energy spectrum which changes smoothly between the Kolmogorov −53 law (no stratification), the −2 scalings of Zhou [Phys. Fluids 7, 2092 (1995)] for the case of strong rotation, as well as the −2 scalings for the case of strong rotation and stratification. For strongly stratified turbulence, the model may give the −2 scaling predicted by Herring [Meteorol. Atmos. Phys. 38, 106 1988], and the −53 scaling indicated by some mesoscale observations.

关键词： Turbulence

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Ka-band SPSTs in InP-based technology using coplanar waveguides

Ka-band SPSTs in InP-based technology using coplanar wavegui...

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Indium Phosphide and Related Materials Conference

作者： V. Ziegler M. Berg H. Tobler C. Wolk R. Deufel J. Dickmann A. Trasser H. Schumacher E. Alekseev D. Pavlidis Research Center Ulm Daimler Benz Aerospace Ulm Germany Department of Electron Devices and Circuits University of Ulm (EBS) Ulm Germany Department of Electrical Engineering and Computer Science University of Michigan Ann Arbor MI USA

Two coplanar Ka-band monolithic integrated SPST switches were designed, fabricated and characterized. The modeling of the coplanar waveguides and discontinuities as well as the comparison with the measured performance of the MMICs is described. InGaAs/InP PIN diodes are used as active switching elements in order to achieve excellent mm-wave performance. The turn-on voltage is 0.4V and a cutoff-frequency of 5.4 THz is achieved. The MMICs demonstrate isolation values as high as 24.4 dB (24.2 dB) and low insertion losses of 0.41 dB (1.13 dB) at the design frequency.

关键词： Coplanar waveguides Diodes Switches Circuit simulation Switching circuits Indium gallium arsenide Indium phosphide Millimeter wave technology Equivalent circuits MMICs

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A Region-Based Representation of Images in MARS

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Journal of VLSI Signal Processing Systems for Signal, Image, and Video Technology 1998年第1-2期20卷 137-150页

作者： Servetto, Sergio D. Rui, Yong Ramchandran, Kannan Huang, Thomas S. Beckman Inst. Adv. Sci. and Technol. Univ. Illinois at Urbana-Champaign Urbana IL 61801 United States Universidad Nacional de La Plata Argentina Univ. Illinois at Urbana-Champaign United States Comp. Res. Adv. Applications Group IBM Argentina Argentina Image Formation and Processing Group Beckman Institute UIUC United States Department of Computer Science UNLP Argentina Dept. of Elec. and Comp. Engineering UIUC United States Multimedia Commun. Res. Department Bell Laboratories Murray Hill NJ United States Info. Sciences Research Department AT and T Labs. Florham Park NJ United States Department of Computer Science UIUC United States Southeast University China Tsinghua University China University of Illinois Urbana-Champaign IL United States Image Formation and Processing Group Beckman Inst. Advance Sci. Technol. UIUC United States Vis. Technol. Grp. of Microsoft Res. Redmond WA United States City College of New York United States Columbia University United States AT and T Bell Labs. United States Ctr. for Telecommunications Research Columbia University United States Elec. and Comp. Eng. Department United States Beckman Institute Coordinated Science Laboratory IL United States IEEE Signal Processing Society United States IEEE IMDSP Technical Committee United States IEEE Transactions on Image Proc. United States National Taiwan University Taipei Taiwan Massachusetts Inst. of Technology Cambridge MA United States Department of Electrical Engineering MIT United States School of Electrical Engineering United States Lab. for Info. and Signal Processing Purdue University United States Dept. of Elec. and Comp. Engineering United States Coordinated Science Laboratory United States Image Formation and Processing Group Beckman Inst. Adv. Sci. and Technol. United States MIT Lincoln Laboratory IBM Thomas J. Watson Research Center Rheinishes Landes Museum Bonn Germany Swiss Institutes of Technology Zurich Switzerland Swiss Institutes of Technology Lausanne S

We study the problem of representing images within a multimedia Database Management System (DBMS), in order to support fast retrieval operations without compromising storage efficiency. To achieve this goal, we propose new image coding techniques which combine a wavelet representation, embedded coding of the wavelet coefficients, and segmentation of image-domain regions in the wavelet domain. A bitstream is generated in which each image region is encoded independently of other regions, without having to explicitly store information describing the regions. Simulation results show that our proposed algorithms achieve coding performance which compares favorably, both perceptually and objectively, to that achieved using state-of-the-art image/video coding techniques while additionally providing region-based support.

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A pseudo-sound constitutive relationship for the dilatational covariances in compressible turbulence

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JOURNAL OF FLUID MECHANICS 1997年 347卷 37-70页

作者： Ristorcelli, JR Institute for Computer Applications in Science and Engineering NASA Langley Research Center Hampton VA 23681 USA

The mathematical consequences of a few simple scaling assumptions regarding the effects of compressibility are explored using a singular perturbation idea and the methods of statistical fluid mechanics. Representations for the pressure-dilatation and dilatational dissipation appearing in single-point moment closures for compressible turbulence are: obtained. The results obtained, in as much as they come from the same underlying procedure, represent a unified development for both dilatational covariances. While the results are expressed in the context of a statistical turbulence closure they provide, with very few phenomenological assumptions, an interesting and clear mathematical model for the 'scalar' effects of compressibility. For homogeneous turbulence with quasi-normal large scales the expressions derived are - in the small turbulent Mach number squared isotropic limit - exact. The expressions obtained contain constants that have a precise physical significance and are defined in terms of integrals of the longitudinal velocity correlation. The pressure-dilatation covariance is found to be a non-equilibrium phenomenon related to the time rate of change of the kinetic energy and internal energy of the turbulence;it is seen to scale with alpha(2)M(t)(2) epsilon(s)[P-k/epsilon - 1](Sk/epsilon(s))(2). Implicit in the scaling is a dependence on the square of a gradient Mach number, Sl/c. A new feature indicated by the analysis is the appearance of the Kolmogorov scaling coefficient, alpha, suggesting that large-scale quantities embodied in the well-established epsilon similar to (u) over tilde(3)/l relationship provide a link to the structural dependence of the effects of compressibility. The expressions for the dilatational dissipation are found to depend on the turbulent Reynolds number and scale as M-t(4)(Sk/epsilon(s))R-4(t)-1. The scalings for the pressure-dilatation are found to produce an excellent collapse of the pressure-dilatation data from direct numerical

关键词： Fluid mechanics

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An introduction to parallel rendering

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PARALLEL COMPUTING 1997年第7期23卷 819-843页

作者： Crockett, TW Institute for Computer Applications in Science and Engineering NASA Langley Research Center Hampton VA 23681-0001 USA

In computer graphics, rendering is the process by which an abstract description of a scene is converted to an image. When the scene is complex, or when high-quality images or high frame rates are required, the rendering process becomes computationally demanding. To provide the necessary levels of performance, parallel computing techniques must be brought to bear. Today, parallel hardware is routinely used in graphics workstations, and numerous software-based rendering systems have been developed for general-purpose parallel architectures. This article provides an overview of the parallel rendering field, encompassing both hardware and software systems. The focus is on the underlying concepts and the issues which arise in the design of parallel renderers. We examine the different types of parallelism and how they can be applied in rendering applications. Concepts from parallel computing, such as data decomposition and load balancing, are considered in relation to the rendering problem. Our survey explores a number of practical considerations as well, including the choice of architectural platform, communication and memory requirements, and the problem of image assembly and display. We illustrate the discussion with numerous examples from the parallel rendering literature, representing most of the principal rendering methods currently used in computer graphics.

关键词： parallel rendering computer graphics survey

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