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Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

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At least 451 records · Page 25
All sourcesNASA NTRSDOE OSTI
NASA NTRS1993

Transformation of two and three-dimensional regions by elliptic systems

During this contract period, our work has focused on improvements to elliptic grid generation methods. There are two principle objectives in this project. One objective is to make the elliptic methods more reliable and efficient, and the other is to construct a modular code that can be incorporated into the National Grid Project (NGP), or any other grid generation code. Progress has been made in meeting both of these objectives. The two objectives are actually complementary. As the code development for the NGP progresses, we see many areas where improvements in algorithms can be made.

Mastin, C. Wayne↗
NASA NTRS2004

Preparing and Analyzing Iced Airfoils

SmaggIce version 1.2 is a computer program for preparing and analyzing iced airfoils. It includes interactive tools for (1) measuring ice-shape characteristics, (2) controlled smoothing of ice shapes, (3) curve discretization, (4) generation of artificial ice shapes, and (5) detection and correction of input errors. Measurements of ice shapes are essential for establishing relationships between characteristics of ice and effects of ice on airfoil performance. The shape-smoothing tool helps prepare ice shapes for use with already available grid-generation and computational-fluid-dynamics software for studying the aerodynamic effects of smoothed ice on airfoils. The artificial ice-shape generation tool supports parametric studies since ice-shape parameters can easily be controlled with the artificial ice. In such studies, artificial shapes generated by this program can supplement simulated ice obtained from icing research tunnels and real ice obtained from flight test under icing weather condition. SmaggIce also automatically detects geometry errors such as tangles or duplicate points in the boundary which may be introduced by digitization and provides tools to correct these. By use of interactive tools included in SmaggIce version 1.2, one can easily characterize ice shapes and prepare iced airfoils for grid generation and flow simulations.

Vickerman, Mary B.↗
NASA NTRS2000

SmaggIce User Guide

SmaggIce (Surface Modeling And Grid Generation for Iced Airfoils) is one of NASNs aircraft icing research codes developed at the Glenn Research Center. It is a software toolkit used in the process of aerodynamic performance prediction of iced airfoils. It includes tools which complement the 2D grid-based Computational Fluid Dynamics (CFD) process: geometry probing; surface preparation for gridding: smoothing and re-discretization of geometry. Future releases will also include support for all aspects of gridding: domain decomposition; perimeter discretization; grid generation and modification.

Baez, Marivell↗
NASA NTRS1990

Computational technology for flight vehicles; Proceedings of the Symposium on Computational Technology on Flight Vehicles, Washington, DC, Nov. 5-7, 1990

The present conference on computational methods for aeronautics applications discusses topics in the fields of parallel computing, multidisciplinary computational methods, grid generation, visualization methods for CFD, probabilistic modeling, numerical simulations and methodologies for different flow regimes, computational strategies and adaptive methods in CFD, and computational strategies and dynamics and control. Attention is given to the MACH system-software kernel, a multidisciplinary approach to aeroelastic analysis, interactive grid generation with control points, interactive flow visualization using stream surfaces, numerical simulations of dynamic/aerodynamic interactions, implicit mathods for the Navier-Stokes equations, and the automatic phase-space analysis of dynamical systems.

Noor, Ahmed K.↗
NASA NTRS1993

Liquid rocket propulsion impeller CFD modeling

Steady-state impeller geometric modeling and typical Navier-Stokes CFD algorithm analysis procedures are assessed using two benchmark quality impeller data sets. Two geometric modeling and grid generation software packages, ICEM-CFD and PATRAN, are considered. Results show that a significant advantage of PATRAN's open-ended architecture is the potential interaction between CFD and structural/thermal analysts inside the mechanical computer-aided engineering environment. However the time required to construct the inducer grid would be unacceptable in a design and engineering environment. The ICEM-CFD package is considered to be more appropriate for structural grid generation but lacks the mature link to structural/thermal analysis arena as compared to PATRAN.

Ratcliff, Mark L.↗
NASA NTRS1992

Using adaptive grid in modeling rocket nozzle flow

The mechanical behavior of a rocket motor internal flow field results in a system of nonlinear partial differential equations which cannot be solved analytically. However, this system of equations called the Navier-Stokes equations can be solved numerically. The accuracy and the convergence of the solution of the system of equations will depend largely on how precisely the sharp gradients in the domain of interest can be resolved. With the advances in computer technology, more sophisticated algorithms are available to improve the accuracy and convergence of the solutions. An adaptive grid generation is one of the schemes which can be incorporated into the algorithm to enhance the capability of numerical modeling. It is equivalent to putting intelligence into the algorithm to optimize the use of computer memory. With this scheme, the finite difference domain of the flow field called the grid does neither have to be very fine nor strategically placed at the location of sharp gradients. The grid is self adapting as the solution evolves. This scheme significantly improves the methodology of solving flow problems in rocket nozzles by taking the refinement part of grid generation out of the hands of computational fluid dynamics (CFD) specialists and place it into the computer algorithm itself.

Chow, Alan S.↗
NASA NTRS1995

A Combined Geometric Approach for Computational Fluid Dynamics on Dynamic Grids

A combined geometric approach for computational fluid dynamics is presented for the analysis of unsteady flow about mechanisms in which its components are in moderate relative motion. For a CFD analysis, the total dynamics problem involves the dynamics of the aspects of geometry modeling, grid generation, and flow modeling. The interrelationships between these three aspects allow for a more natural formulation of the problem and the sharing of information which can be advantageous to the computation of the dynamics. The approach is applied to planar geometries with the use of an efficient multi-block, structured grid generation method to compute unsteady, two-dimensional and axisymmetric flow. The applications presented include the computation of the unsteady, inviscid flow about a hinged-flap with flap deflections and a high-speed inlet with centerbody motion as part of the unstart / restart operation.

Slater, John W.↗
NASA NTRS1994

CFD analyses for advanced pump design

As one of the activities of the NASA/MSFC Pump Stage Technology Team, the present effort was focused on using CFD in the design and analysis of high performance rocket engine pumps. Under this effort, a three-dimensional Navier-Stokes code was used for various inducer and impeller flow field calculations. An existing algebraic grid generation procedure was-extended to allow for nonzero blade thickness, splitter blades, and hub/shroud cavities upstream or downstream of the (main) blades. This resulted in a fast, robust inducer/impeller geometry/grid generation package. Problems associated with running a compressible flow code to simulate an incompressible flow were resolved; related aspects of the numerical algorithm (viz., the matrix preconditioning, the artificial dissipation, and the treatment of low Mach number flows) were addressed. As shown by the calculations performed under the present effort, the resulting code, in conjunction with the grid generation package, is an effective tool for the rapid solution of three-dimensional viscous inducer and impeller flows.

Dejong, F. J.↗
NASA NTRS1988

Influence of the structure of inlet free-stream turbulence on diffuser performance

The pressure recovery coefficient of a two-dimensional diffuser (Cp) was found to be significantly affected by the intensity and structure of the inlet free-stream turbulence. Significantly larger values of Cp occurred for the case of highly anisotropic inlet free-stream turbulence with the plane of rotation of the eddies parallel to the free-stream flow and perpendicular to the diverging walls of the diffuser, as compared to the values of Cp for the case of grid-generated near-isotropic inlet conditions. The relatively high values of Cp for the case of the highly anisotropic inlet free-stream turbulence conditions can be attributed to highly effective mixing, where the plane of rotation of the eddies facilitates a direct transport of momentum from the free-stream to the boundary layers along the diverging walls of the diffuser, as compared to the mixing that occurs with grid-generated highly unorganized eddies.

Hoffmann, Jon A.↗
NASA NTRS1986

High speed viscous flow calculations about complex configurations

Applications of the NASA Ames Parabolized Navier-Stokes (PNS) code to a variety of complex generic configurations is presented. The algorithm, boundary conditions, initial conditions, and grid generators are discussed as applied to these configurations. The PNS code was used as the mainline procedure to numerically simulate the viscous supersonic flow over these generic configurations. The turbulence model that was used in this study is the Baldwin-Lomax model. The boundary conditions are the usual viscous no slip at the wall, and a characteristic procedure is used to fit the bow shock wave which is the outermost boundary. An elliptic grid generator is employed to discretize the flow domain. In addition, an equilibrium air capability has been incorporated into the code. It uses the curve fits of Tannehill, et al. The flow regimes vary from a Mach number of 2 up to 25. Both laminar and turbulent flow are considered. Varying angles of attack have also been computed. Configurations vary from simple cone-type bodies to lifting winged bodies, such as the space shuttle or the generic supersonic cruise fighter.

Chaussee, D. S.↗
NASA NTRS1995

NASA-IGES Translator and Viewer

NASA-IGES Translator (NIGEStranslator) is a batch program that translates a general IGES (Initial Graphics Exchange Specification) file to a NASA-IGES-Nurbs-Only (NINO) file. IGES is the most popular geometry exchange standard among Computer Aided Geometric Design (CAD) systems. NINO format is a subset of IGES, implementing the simple and yet the most popular NURBS (Non-Uniform Rational B-Splines) representation. NIGEStranslator converts a complex IGES file to the simpler NINO file to simplify the tasks of CFD grid generation for models in CAD format. The NASA-IGES Viewer (NIGESview) is an Open-Inventor-based, highly interactive viewer/ editor for NINO files. Geometry in the IGES files can be viewed, copied, transformed, deleted, and inquired. Users can use NIGEStranslator to translate IGES files from CAD systems to NINO files. The geometry then can be examined with NIGESview. Extraneous geometries can be interactively removed, and the cleaned model can be written to an IGES file, ready to be used in grid generation.

Chou, Jin J.↗
NASA NTRS1995

3DGRAPE/AL User's Manual

This document is a users' manual for a new three-dimensional structured multiple-block volume g generator called 3DGRAPE/AL. It is a significantly improved version of the previously-released a widely-distributed programs 3DGRAPE and 3DMAGGS. It generates volume grids by iteratively solving the Poisson Equations in three-dimensions. The right-hand-side terms are designed so that user-specific; grid cell heights and user-specified grid cell skewness near boundary surfaces result automatically, with little user intervention. The code is written in Fortran-77, and can be installed with or without a simple graphical user interface which allows the user to watch as the grid is generated. An introduction describing the improvements over the antecedent 3DGRAPE code is presented first. Then follows a chapter on the basic grid generator program itself, and comments on installing it. The input is then described in detail. After that is a description of the Graphical User Interface. Five example cases are shown next, with plots of the results. Following that is a chapter on two input filters which allow use of input data generated elsewhere. Last is a treatment of the theory embodied in the code.

Sorenson, Reese L.↗
NASA NTRS1993

Advancing-layers method for generation of unstructured viscous grids

A novel approach for generating highly stretched grids which is based on a modified advancing-front technique and benefits from the generality, flexibility, and grid quality of the conventional advancing-front-based Euler grid generators is presented. The method is self-sufficient for the insertion of grid points in the boundary layer and beyond. Since it is based on a totally unstructured grid strategy, the method alleviates the difficulties stemming from the structural limitations of the prismatic techniques.

Pirzadeh, Shahyar↗
DOE OSTI2021

New Jersey Transit Grid Distributed Generation Program. Cybersecurity Design Assurance Assessment

Superstorm Sandy caused a major disruption to passenger-rail and other commuter systems throughout New York and New Jersey. To address this issue, New Jersey Transit (NJT) established the NJ TRANSITGRID project, an effort designed to power bus, ferry, and limited passenger-rail service during natural or man-made disasters. Given the importance of these transportation systems, NJT partnered with Sandia National Laboratories (Sandia) to assess the cyber-resilience of the information systems that monitor and control the electrical systems within the microgrid. The Sandia “tabletop” assessment is based on the most recent 20% design packages. From this assessment, the Sandia team identified several security areas that were undefined or did not implement industry best practices. Finally, the Sandia team presented possible follow-on assessment activities and recommended investigating multiple hardening technologies. Addressing these findings and adding state-of-the-art detection and mitigation technologies will help ensure the NJ TRANSITGRID is built with more comprehensive cyber-resilience features.

24 POWER TRANSMISSION AND DISTRIBUTION↗
NASA NTRS1983

Parallel architectures for iterative methods on adaptive, block structured grids

A parallel computer architecture well suited to the solution of partial differential equations in complicated geometries is proposed. Algorithms for partial differential equations contain a great deal of parallelism. But this parallelism can be difficult to exploit, particularly on complex problems. One approach to extraction of this parallelism is the use of special purpose architectures tuned to a given problem class. The architecture proposed here is tuned to boundary value problems on complex domains. An adaptive elliptic algorithm which maps effectively onto the proposed architecture is considered in detail. Two levels of parallelism are exploited by the proposed architecture. First, by making use of the freedom one has in grid generation, one can construct grids which are locally regular, permitting a one to one mapping of grids to systolic style processor arrays, at least over small regions. All local parallelism can be extracted by this approach. Second, though there may be a regular global structure to the grids constructed, there will be parallelism at this level. One approach to finding and exploiting this parallelism is to use an architecture having a number of processor clusters connected by a switching network. The use of such a network creates a highly flexible architecture which automatically configures to the problem being solved.

Gannon, D.↗