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

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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Applying fuzzy functions and sequential coordination to optimization of machinery arrangement and pipe routing

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NAVAL ENGINEERS JOURNAL 1998年第6期110卷 43-54页

作者： Wu, BC Young, GS Schmidt, W Choppella, K Dr. Bi-Chu Wu:received a PhD in Mechanical Engineering from the University of Maryland College Park in 1991. She has worked on projects involving naval architecture design optimization solid mechanics and database development. Presently a senwr engineer with Angle Incorporated Dr Wu's research interests are in design optimization and fuzzy logic applications. Dr. Gin-Shu Young: a senior engineer with Angle Incorporated holds a PhD in Mechanical Engineering from the University of Maryland College Park. As a guest researcher with National Institute of Standards and Technologies from 1990 to 1993 he worked on vision-based navigation for autonomous vehicles. His experience also includes applications of optimization fuzzy logic neural network and genetic algorithm methods to engineering system design Mr. William Schmidt:co-founded Angle Incorporated in 1990 and has served as Vice PresidentlChiefScientist during this tame. He holds a B.Sc. in Applied Science from the Naval Acadt?my and an M.Sc. in Physics from the Naval Post Graduate School. He has cner 20 years experience in technical leadership material and personnel management. He has led the application of computer aided design (CAD) and Product Model Information Exchange to the shipbuilding industry. His experience also includes leading the amlication of model based operational analysis to support the Live Fire Test Program for DDG 51 Class Destroyers. Mr. Krishna M. Choppella:is a Sofware Engineer at Eidea Laboratories Incotporated where he works on componentbased distributed enterpvise frameworks. He has been involved in creating data analysis tools for the US Nay by integrating CAD modeis databases and graphical front ends. His work in the Masters degree program in Mechanical Engineering at the University of Texas at Austin was in di0ddase.r spectroscopy of combustion products in porous-matri burners. He received his Bachelors degree in Electrical Engineering in India. He was a Research Associate at the Centre for Laser Technology and Project Engi

Ship design is often multidisciplinary involving several design elements with various types of objectives and constraints (O/C) some easily described as mathematical formulas, others better modeled as descriptive assertions. This paper describes a method based on fuzzy functions and an integrated performance index to model O/C using descriptive assertions to be used with mathematical formulas in optimization. Another issue addressed in this paper concerns the coordination of design elements when sequentially coupled, that is, when one leads the other and the performance of the follower depends greatly on the design of the leader. Based on neuro-fuzzy techniques, the method described here coordinates and optimizes sequentially coupled elements. The two methods are applied to machinery arrangement (MA) and pipe routing (PR). Preliminary models for optimization of MA and PR are described considering convenience, producibility: engine room size, interference and location as factors in the O/C set. Some test results from MA/PR applications are presented and discussed. The methods are generic and can be extended to other elements in ship design. They are mutually independent and may be used separately Two advantages of their use are an improvement in overall performance and a reduction in the need for redesign of elements.

关键词： Optimization

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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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A Galilean invariant explicit algebraic Reynolds stress model for turbulent curved flows

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PHYSICS OF FLUIDS 1997年第4期9卷 1067-1077页

作者： Girimaji, SS Institute for Computer Applications in Science and Engineering NASA Langley Research Center Hampton Virginia 23681

A Galilean invariant weak-equilibrium turbulence hypothesis that is sensitive to streamline curvature is proposed. The hypothesis leads to a fully explicit algebraic expression for Reynolds stress in terms of the mean velocity field and kinetic energy and dissipation of turbulence. The model is tested in curved homogeneous shear flow which is a homogeneous idealization of the circular streamline flow. The agreement is excellent with Reynolds stress closure model and adequate with available experimental data.

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Computational issues in damping identification for large scale problems

Computational issues in damping identification for large sca...

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ASME 1997 Design engineering Technical Conferences, DETC 1997

作者： Pilkey, Deborah F. Roe, Kevin P. Inman, Daniel J. Engineering Science and Mechanics Virginia Tech BlacksburgVA24061-0219 United States Institute for Computer Applications in Science and Engineering HamptonVA23681-0001 United States

ISBN: (纸本)9780791880425

Damage detection and diagnostic techniques using vibration responses that depend on analytical models provide more information about a structure's integrity than those that are not model based. The drawback of these approaches is that some form of a workable model is required. Typically, models of practical structures and their corresponding computational effort are very large. One method of detecting damage in a structure is to measure excess energy dissipation, which can be seen in damping matrices. Calculating damping matrices is important because there is a correspondence between a change in the damping matrix and the change in the health of a structure. The objective of this research is to investigate the numerical problems associated with computing damping matrices using inverse methods. Two damping identification methods are tested for efficiency in large-scale applications. One is an iterative routine, and the other a least squares method. Numerical simulations have been performed on multiple degree-of-freedom models to test the effectiveness of the algorithm and the usefulness of parallel computation for the problems. High Performance Fortran is used to parallelize the algorithm. © 1997 American Society of Mechanical Engineers (ASME). All rights reserved.

关键词： Energy dissipation

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Simulation of a controlled airfoil with jets 35th

Simulation of a controlled airfoil with jets

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35th Aerospace sciences Meeting and Exhibit, 1997

作者： Allan, Brian G. Holt, Maurice Packard, Andrew Institute for Computer Applications in Science and Engineering HamptonVA23681 United States Dept. of Mechanical Engineering University of California BerkeleyCA94720 United States

Numerical simulation of a two-dimensional airfoil, controlled by an applied moment in pitch, and an airfoil controlled by jets are investigated. These simulations couple the Reynolds-averaged Navier Stokes equations and Euler’s equations of rigid body motion with an active control system. The simulation of a step in commanded altitude was performed for both systems with a free steam Mach number of 0.3. The airfoil controlled by a pitching moment used an optimal state feedback controller. The feedback gains were calculated using a Linear Quadratic Regulator method. The simulation of the coupled system compared very well with a quasi-steady aerodynamic model showing a measure of validation for the coupled system. Robust control design methods were used to develop a controller for the airfoil with jets. The linear model used to design the robust controller was identified from input/output data generated by open-loop simulations of the coupled system. Simulation of the airfoil with jets showed good tracking of the desired altitude trajectory with oscillations in the attitude and vertical velocity. The results of this research begin to provide a control system designer with a means of computationally evaluating an aircraft control system in problematic nonlinear flight regimes. © 1997, American institute of Aeronautics and Astronautics, Inc.

关键词： Airfoils

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Multigrid strategies for viscous flow solvers on anisotropic unstructured meshes 13th

Multigrid strategies for viscous flow solvers on anisotropic...

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13th Computational Fluid Dynamics Conference, 1997

作者： Mavriplis, D.J. Institute for Computer Applications in Science and Engineering NASA Langley Research Center MS 132C HamptonVA23681-0001 United States

Unstructured multigrid techniques for relieving the stiffness associated with high-Reynolds number viscous flow simulations on extremely stretched grids are investigated. One approach consists of employing a semi-coarsening or directional-coarsening technique, based on the directions of strong coupling within the mesh, in order to construct more optimal coarse grid levels. An alternate approach is developed which employs directional implicit smoothing with regular fully coarsened multigrid levels. The directional implicit smoothing is obtained by constructing implicit lines in the unstructured mesh based on the directions of strong coupling. Both approaches yield large increases in convergence rates over the traditional explicit full-coarsening multigrid algorithm. However, maximum benefits are achieved by combining the two approaches in a coupled manner into a single algorithm. An order of magnitude increase in convergence rate over the traditional explicit full-coarsening algorithm is demonstrated, and convergence rates for high-Reynolds number viscous flows which are independent of the grid aspect ratio are obtained. Further acceleration is provided by incorporating low-Mach-number preconditioning techniques, and a Newton-GMRES strategy which employs the multigrid scheme as a preconditioner. The compounding effects of these various techniques on speed of convergence is documented through several example test cases. © 1997 by the American institute of Aeronautics and Astronautics, Inc. All rights reserved.

关键词： Coarsening

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Adaptive meshing techniques for viscous flow calculations on mixed element unstructured meshes 35th

Adaptive meshing techniques for viscous flow calculations on...

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35th Aerospace sciences Meeting and Exhibit, 1997

作者： Mavriplis, D.J. Institute for Computer Applications in Science and Engineering MS 132C NASA Langley Research Center HamptonVA23681-0001 United States

An adaptive refinement strategy based on hierarchical element subdivision is formulated and implemented for meshes containing arbitrary mixtures of tetrahedra, hexahedra, prisms, and pyramids. Special attention is given to keeping memory overheads as low as possible. This procedure is coupled with an algebraic multigrid flow solver which operates on mixed-element meshes. Inviscid flows as well as viscous flows are computed on adaptively refined tetrahedral, hexahedral, and hybrid meshes. The efficiency of the method is demonstrated by generating an adapted hexahedral mesh containing 3 million vertices on a relatively inexpensive workstation. © 1997 American institute of Aeronautics and Astronautics, Inc. All rights reserved.

关键词： Viscous flow

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Development and application of a dilatational covariances model for compressible mixing layers 35th

Development and application of a dilatational covariances mo...

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35th Aerospace sciences Meeting and Exhibit, 1997

作者： Thangam, S. Ristorcelli, J.R. Zhou, Y. Institute for Computer Applications in Science and Engineering NASA Langley Research Center HamptonVA23681 United States Department of Mechanical Engineering Stevens Institute of Technology HobokenNJ07030 United States

A dilatational covariances model based on a pseudosound constitutive relation is developed in conjunction with a recursion renormalization group (r-RNG) based anisotropic Reynolds stress closure. The model is applied for the prediction of turbulent compressible mixing layers. The calculations are used to evaluate the complex physical phenomena affecting compressible mixing layers. The rate of growth of the mixing layer is retarded by the combined effects of compressible dissipation, the pressure-dilatational covariances, and the anisotropic turbulence stresses. The pressure-dilatational, essentially a nonequilibrium effect, reduces the amount of excess production over dissipation available for the turbulence energy growth. The influence of anisotropic Reynolds stress is analyzed. All coefficients in the model and used in these computations are predicted by the theory. © 1997, American institute of Aeronautics and Astronautics, Inc.

关键词： Reynolds number

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Textbook multigrid efficiency for the steady euler equations 13th

Textbook multigrid efficiency for the steady euler equations

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13th Computational Fluid Dynamics Conference, 1997

作者： Roberts, Thomas W. Sidilkover, David Swanson, R.C. NASA Langley Research Center United States Institute for Computer Applications in Science and Engineering United States NASA Langley Research Center HamptonVA United States

A fast multigrid solver for the steady incompressible Euler equations is presented. Unlike timemarching schemes, this approach uses relaxation of the steady equations. Application of this method results in a discretization that correctly distinguishes between the advection and elliptic parts of the operator, allowing efficient smoothers to be constructed. Solvers for both unstructured triangular grids and structured quadrilateral grids have been written. Computations for channel Sow and now over a nonhfting airfoil have computed. Using Gauss-Seidel relaxation ordered in the Sow direction, textbook multigrid convergence rates of nearly one order-of-magnitude residual reduction per multigrid cycle are achieved, independent of the grid spacing. This approach also may be applied to the compressible Eider equations and the incompressible Navier-Stokes equations. © 1997, American institute of Aeronautics and Astronautics, Inc.

关键词： Textbooks

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