Chimera Grid Tools (CGT) is a software package containing a variety of tools for the Chimera overset grid approach [1] for solving complex configuration problems. Several examples of recent computations that used Chimera Grid Tools for the creation of the grid systems are shown on Figure 1. The current procedure for performing overset CFD analysis on such configurations is outlined in Figure 2. A typical starting point is a description of the surface geometry in CAD format, while typical outputs from the process are force and moment coefficients, pressure distributions, etc. of the configuration under certain specified free stream conditions. The complete suite of tools necessary to perform such a process includes CAD tools for geometry manipulation, and geometry defects elimination, Chimera Grid Tools for grid generation and post-processing, PEGASUS [2], DCF3D [3,4], (or other equivalent tool) for domain connectivity, OVERFLOW [5] for solution computation, and FOMOCO Utilities [6, 7], or USURP [8] for force and moment computation. Individual tools used in various parts of the process are illustrated in red in Figure 2.
 |
Space Shuttle Launch Vehicle and Debris Trajectory Analyses (Reynaldo J. Gomez, et. al., NASA Johnson Space Center) |
|---|---|
 |
Subsonic Transport with Propulsion and High Lift Devices (Stuart E. Rogers., NASA Ames Research Center) |
 |
X-38 V-131R Crew Return Vehicle (James S. Greathouse, NASA Johnson Space Center) |
 |
RLV Baseline Turbopump (Cetin Kiris, NASA Ames Research Center) |
 |
V-22 Tiltrotor (Robert L. Meakin, Army Aeroflightdynamics Directorate) |
 |
Comanche (Robert L. Meakin, Army Aeroflightdynamics Directorate) |
 |
Trapezoidal Wing High-Lift Configuration (Steven M. Nash, MCAT, Inc., NASA Ames Research Center) |
Tools in CGT can be grouped into the following categories: surface grid generation tools, volume grid generation tools, grid utilities, configuration automation scripts, utility scripts, and post-processing tools. See Table 1 below for a brief description of each tool, the category for which it resides, and access to more detailed documentation. The package is organized with the following directories:
The doc directory contains documentation and sample input files for the various grid tools and scripts, as well as a log of the changes made for each release of CGT.
The examples directory contains a suite of examples to test the tools, and also includes a self-verification tool named verify to check that the tools are running properly.
The gui directory contains files for a graphical user interface called OVERGRID [9,10] that can be used to access the various grid tools. For a user facing a new problem, it is much easier to perform grid generation with the assistance of a graphical tool for the first time. Once the gridding strategy has been identified, scripts can be constructed to generate grids for similar configurations.
The include directory contains header files that are included into various source code files through use of the preprocessor.
The lib directory contains libraries of FORTRAN and C routines that are common to many of the grid tools. These routines include computation of stretching functions, computation of grid normals, projections of grids, grid topology determination and enforcement, and many others.
The scriptbin directory contains a number of Tcl scripts which can automate the building of an overset grid system following the process illustrated in Figure 2. These scripts will build input files, execute, and provide error checking for a number of programs, including: volume grid generation ( HYPGEN [11,12] and LEGRID), volume grid smoothing ( SMOGRD), domain connectivity using PEGASUS 5.0 (complete input file) or PEGSUS 4.1 (partial input file) [2], surface fringe point projection ( PROGRD), hybrid surface grid generation for force and moment computation [6, 7], flow solution computation using OVERFLOW [5]. See the scripts manual for more details. Such scripts have been used to create complex grid systems for high-lift configurations [13].
The scriptlib directory contains a library of Tcl language script procedures that are called by some of the scripts in the scriptbin directory, and are available to the user by using the lappend auto_path scriptlib command. These procedures are also highly useful when building specific grid generation scripts.
The src directory contains the source code for the high-level batch-mode FORTRAN codes that can be run by the user.
Below is a figure showing the hierarchy of the various modules in the Chimera Grid Tools package:
 |
OVERGRID - Graphical user interface for visualization and processing of geometry and grids, grid generation, domain connectivity and flow solver input preparation |
|---|
| Color | Category | Color | Category |
|---|---|---|---|
| - | Surface Grid Generation | - | Volume Grid Generation |
| - | Grid Utility | - | Configuration Automation Script |
| - | Utility Script | - | Post Processing |
| Program | Description |
|---|---|
| autobc | Automatic boundary conditions determination |
| boxgr | Generation of stretched cartesian background grids and elliptic far-field grids |
| BuildIngrid | Builds the INGRID file used by PEGSUS 4.1 |
| BuildMixsuri | Builds the MIXSUR/OVERINT input file from OVERFLOW input files |
| BuildOveri | Builds the OVERFLOW input files from individual "stubs" |
| BuildPegi/BuildPeg5i | Builds the PEGSUS 4.1/5.0 input file template (no hole boundaries for 4.1) |
| BuildPlot | Creates a PLOT3D command file to view family and boundary condition surfaces. Can also be used in a standalone mode with just an OVERFLOW input file. Type "BuildPlot -help" for documentation on its command-line parameters. |
| BuildProgrdi | Builds the PROGRD input file from the OVERFLOW input file information |
| BuildSurf | Runs 'make' for each component grid to update configuration surface grids |
| BuildVol | Creates volume grids via either makevol or boxgr |
| cad2srf | Generate surface triangulation and edge curves from native solid CAD part |
| cgtclean | Cleans output from most CGT tools |
| collar | Script to create collar grids [14] |
| combinemx | Combine any number of PLOT3D grid files into one PLOT3D multiple grid file |
| combinemq | Combine any number of PLOT3D Q files into one PLOT3D multiple grid Q file |
| compx | Computation of difference between two grids |
| conmug | Auto-concatenation of multiple surface and curve grids |
| curvar | Computation of areas bounded by one or more closed curves in an x, y, or z constant plane |
| extractsrf | Parses MIXSUR input file to create SPLITMX/SPLITMQ inputs for just surface info |
| gencore | Generation of H-topology volume grid inside core of a tube |
| genpipe | Generation of constant diameter pipe surface grid from 3-D centerline curve |
| gen_x | Domain connectivity pre-processing tool for creating object images |
| grided | Compilation of a variety of grid editing functions for structured grids |
| gridinf | Computes basic grid information |
| hypgen | Generation of a hyperbolic volume grid from a single surface grid [11,12] |
| hypin | Generation of normal spacing function for volume grids |
| intchk | Interpolation stencil quality check using fringe point coordinates |
| intgrd | Generation of a new surface grid onto a reference grid via interpolation |
| loadis | Computation of sectional force coefs on components |
| lsect | Find intersection curve between one intersector surface grid and multiple intersectee surface grids |
| makevol | Creates a volume grid via HYPGEN/LEGRID, and runs SMOGRD using OVERFLOW input file |
| minterp | Interpolation of single/multiple grid and solution files |
| mixsur | Generation of hybrid surface grid for force/moment computation |
| overhist | Extraction of residual and flow coefficients data from OVERFLOW history files |
| overint | Integration of force/moment and mass flow rate coefficients |
| overplot | GUI for plotting flow coefficients and sectional Cp cuts on components |
| pip | Mass properties calculator |
| plothole | Creates PLOT3D command file for PEGSUS 4.1 boundaries |
| PreVol | Builds OVERFLOW input files, config.tcl, inputs.tcl from surface grid file |
| p3dConvert | Convert PLOT3D grid and q files and OVERFLOW-2 q files between big and little endian formats |
| p3dtrans | Conversion of PLOT3D format for curve grids to/from 2/3-column xyz data format |
| progrd | Projection of points onto a collection of reference grids |
| recurv | Grid-point redistribution |
| reord | Grid-point re-ordering for a single grid-line |
| RunPeg | Runs BuildIngrid, pegsus41, and PROGRD using configuration information |
| sblock | Partial surface domain decomposition and grid generation [15] |
| ScriptClean | Cleans up .srf, .vol, .mvlog, etc. files for an entire configuration |
| scriptlib | Script library containing many Tcl procedures for grid scripts |
| seamcr | Automatic seam curve extraction and spider web grid generation [16] |
| seamcrt | Surface curves creation on surface triangulations |
| setzeta | Generate normal grid-spacing file zetastr.i for HYPGEN program |
| shftgrd | Shifting/translating grid coordinates of a specified subset |
| smogrd | Perform elliptic smoothing in selected grid subset to spread out region of fine spacing |
| smooth | Smooth grid by performing second order smoothing |
| smosurf | Perform grid spacing smoothing in one direction for volume grids |
| splitmx | Extraction of arbitrary grid subsets from PLOT3D multiple grid file |
| splitmq | Extraction of arbitrary q subsets from PLOT3D multiple grid q file |
| srap | Perform splining, grid point redistribution and projection on curves/surfaces |
| str2tri | Convert PLOT3D multiple structured surface panels to CART3D surface triangulation |
| strchk | Computation and display of local stretching ratio info for grids |
| stretch | Evaluation and display of 1D stretching functions |
| srf2cad | Project structured surface grid back to native solid CAD part |
| surgrd | Generation of a new surface grid onto a collection of reference grids via hyperbolic/algebraic surface grid generation [17] |
| Tscan | Computation of cross sectional area of a triangulated object versus x, y or z |
| triged | Compilation of a variety of grid editing functions for surface triangulations |
| usurp | Integration of force/moment and mass flow rate coefficients on overset surface grids using polygon clipping |
| vpro | Interpolate velocity profiles from a grid and solution at specified surface normals or lines |
| wingcap | Generation of surface grid in tip region of wing |
| wkcut | Generation of surface grid in wake region |
| xinted | Perform various combination functions to grid, XINTOUT and INS3D bc files |
| xrayed | Split and combine multiple Xray files with multiple Xrays in each |
Many people have contributed to the different parts of Chimera Grid Tools. A summary of the tools/scripts and their application is shown in Table 1. See the documentation for the individual tool to determine authorship. Questions and suggestions can be directed to the corresponding authors (see Table 2).
| Name | Affiliation | E-mail address |
|---|---|---|
| William M. Chan | NASA Ames Research Center, TNA Branch | wchan@nas.nasa.gov |
| Stuart E. Rogers | NASA Ames Research Center, TNA Branch | rogers@nas.nasa.gov |
| Steven M. Nash * | ELORET, NASA Ames Research Center, INA Branch | - |
| Pieter G. Buning | NASA Langley Research Center | Pieter.G.Buning@nasa.gov |
| Robert L. Meakin | Army Aeroflightdynamics Directorate | bmeakin@mail.arc.nasa.gov |
| David A. Boger | Penn State University Applied Research Laboratory | dab143@only.arl.psu.edu |
| Shishir Pandya | NASA Ames Research Center, TNA Branch | pandya@nas.nasa.gov |
* no longer working on project
Enter keywords for searching:
NOTICES
Chimera Grid Tools Copyright © 2004, 2007 United States Government as represented by the Administrator of the National Aeronautics and Space Administration. No copyright is claimed in the United States under Title 17, U.S. Code. All Other Rights Reserved.
Unique Surface Using Ranked Polygons (USURP) distributed under license by the Pennsylvania State Research Foundation. Portions of USURP created by David Boger are Copyright © 2005 The Pennsylvania State University. All Rights Reserved.
This software may be used, copied, and provided to others only as permitted under the terms of the contract or other agreement under which it was acquired from the U.S. Government. If you have received this software for use under a Government Contract, Cooperative Agreement or Grant the software is for federal government research purposes only, and may not be further distributed to third parties. Neither title to nor ownership of the software is hereby transferred. This notice shall remain on all copies of the software.
DISCLAIMERS
THE SOFTWARE IS PROVIDED "AS IS" WITHOUT ANY WARRANTY OF ANY KIND, EITHER EXPRESSED, IMPLIED, OR STATUTORY, INCLUDING, BUT NOT LIMITED TO, ANY WARRANTY THAT THE SOFTWARE WILL CONFORM TO SPECIFICATIONS, ANY IMPLIED WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE, OR FREEDOM FROM INFRINGEMENT, ANY WARRANTY THAT THE SOFTWARE WILL BE ERROR FREE, OR ANY WARRANTY THAT DOCUMENTATION, IF PROVIDED, WILL CONFORM TO THE SOFTWARE. IN NO EVENT SHALL THE UNITED STATES GOVERNMENT, OR ITS CONTRACTORS OR SUBCONTRACTORS, BE LIABLE FOR ANY DAMAGES, INCLUDING, BUT NOT LIMITED TO, DIRECT, INDIRECT, SPECIAL OR CONSEQUENTIAL DAMAGES, ARISING OUT OF, RESULTING FROM, OR IN ANY WAY CONNECTED WITH THIS SOFTWARE, WHETHER OR NOT BASED UPON WARRANTY, CONTRACT, TORT, OR OTHERWISE, WHETHER OR NOT INJURY WAS SUSTAINED BY PERSONS OR PROPERTY OR OTHERWISE, AND WHETHER OR NOT LOSS WAS SUSTAINED FROM, OR AROSE OUT OF THE RESULTS OF, OR USE OF, THE SOFTWARE OR SERVICES PROVIDED HEREUNDER. THE UNITED STATES GOVERNMENT DISCLAIMS ALL WARRANTIES AND LIABILITIES REGARDING THIRD PARTY SOFTWARE, IF PRESENT IN THE NASA GENERATED SOFTWARE, AND DISTRIBUTES IT "AS IS."
RECIPIENT AGREES TO WAIVE ANY AND ALL CLAIMS AGAINST THE UNITED STATES GOVERNMENT AND ITS CONTRACTORS AND SUBCONTRACTORS, AND SHALL INDEMNIFY AND HOLD HARMLESS THE UNITED STATES GOVERNMENT AND ITS CONTRACTORS AND SUBCONTRACTORS FOR ANY LIABILITIES, DEMANDS, DAMAGES, EXPENSES OR LOSSES THAT MAY ARISE FROM RECIPIENT'S USE OF THE SOFTWARE, INCLUDING ANY DAMAGES FROM PRODUCTS BASED ON, OR RESULTING FROM, THE USE THEREOF.
IF FURTHER RELEASE OR DISTRIBUTION OF THIS SOFTWARE OR TECHNICAL DATA DERIVED FROM THIS SOFTWARE IS PERMITTED, RECIPIENT AGREES TO OBTAIN THIS IDENTICAL WAIVER OF CLAIMS, INDEMNIFICATION AND HOLD HARMLESS AGREEMENT WITH ANY ENTITIES THAT ARE PROVIDED WITH THE SOFTWARE OR TECHNICAL DATA DERIVED FROM THE SOFTWARE.