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a. MESH Æ MAP, FACE_PROJECT_TO_SURFACE change to 0
b. MESH Æ FACE, EXACT_MESH_EVALS change to 1
6. Face Meshing with Tri Scheme
The maximum number of tri elements on a single face is limited to 500000. This limit can be adjusted by resetting the value of MAX_FACES under MESH Æ TRIMESH.
Introduction
GAMBIT provides many important tools for geometry creation and meshing. In most of the cases, you do not have to change the defaults. However, optimal creation of certain geometries and meshes may require modifications to the default settings.
Frequently Modified Defaults in GAMBIT
Purpose: This document contains a list of defaults in GAMBIT that may be modified in order to control the behavior of the program such as GUI layout, graphics display, and smoothing characteristics for meshing algorithms. Situations where these changes in defaults may be helpful are discussed, with examples.
9. Node Placements after Meshing a Face
An exact projection from facets to a real surface can lead to distorted and highly skewed meshes for complex/curved geometries. The default value for MESH Æ FACE Æ PROJECT_TO_SURFACE can be changed from 1 to 0 to suppress exact projection.
PYRAMID_INSERT_TET
PYRAMID_OFFSET_METHOD
8. Size Function Background Grid
In many cases, when sizing functions are used while meshing, the background grid is not resolved properly or is under-resolved.
3. Splitting Virtual Geometries
Splitting of virtual geometries is not enabled by default. To split virtual geometry with a real or virtual entity, change the default value of VIRTUAL_FACE_FACE_SPLIT from 0 to 1 under GEOMETRY Æ FACE.
To improve mesh quality, increase the value of TOOLSÆ SFUNCTION Æ BGRID_MAX_TREE_DEPTH from default value of 16 to an acceptable value that will help in obtaining a better quality mesh. A value of –1 puts no limits on the background tree depth, but makes Size Functions slow for larger models. The above figures show the background grid with BGRID_MAX_TREE_DEPTH value of 16 and 19 respectively.
2. Undo Levels
The default number of UNDO levels is 10, but can be increased or reduced by modifying the value of the default for LEVEL under GLOBAL Æ UNDO category. A lower value may be necessary for large models to reduce the memory ity
The default scheme used for examining the mesh is equisize skewness, which is accessible through Mesh Æ Volume Æ Check Volume Meshes. The default scheme can be changed by modifying the value of ELEMENT_3D_QUALITY default under MESH Æ EXAMINE. The corresponding default for 2D is ELEMENT_2D_QUALITY. The available methods are listed against the corresponding variable.
Product Version: GAMBIT 2.3 and onward Authors: Shariq M. Khan and Ajay Parihar
5. Face Meshing with Map Scheme
While generating a mapped mesh on small scale geometries (of the order of 1e-5 or lower), GAMBIT may generate distorted or irregular cells at the face corners. This problem can be rectified by modifying either one of the following defaults:
PYRAMID_OFFSET_DISTANCE
Significance
Defines the height of pyramids and thereby affects their quality. Try values similar to the size of the quad cells if the default fails. Controls insertion of a tetrahedral cell between two pyramids during initialization. The default option is Off. If initialization fails, turn this option On. Skewness-based default method for growing pyramids. Use the neighbor method if the default fails.
Smoothing Option in Cooper Tool
If the area/shape of source faces is significantly different, the Cooper scheme may generate highly skewed elements. In such situations, it is recommended to disable the SMOOTH_PROJECTED_FACE_MESH option under MESH Æ COOPER by resetting the value to 0
7. Pyramid-Related Options for Tetrahedral Meshing
GAMBIT will grow a transition layer of pyramids while generating tetrahedral elements on a three-
dimensional geometry with quadrilateral elements on the faces. This operation may fail in situations where the quad elements have large aspect ratio. A remedy is to change the following defaults in the MESH Æ TETMESH section. Parameter
11. Exporting 2D Mesh
If the mesh lies in a plane parallel to the XY plane within a specified tolerance value (default is 0.0001), the 2D mesh can be exported from GAMBIT. To export the 2D mesh, the maximum and minimum zcoordinate of the nodes should be less than the default value. The default tolerance value can be changed using the FILE_IO.MESH.EXPORT_2D_TOLERANCE option.
1. Background of Graphics
The default background color in GAMBIT is black. You can modify it by specifying the required color in WINDOWS_BACKGROUND_COLOR default under GRAPHICS Æ GENERAL.
4. Edge Meshing on a Mapped Face
Use of the MAP meshing scheme on a face requires the same node count on the opposite edges. If one of the edges is premeshed with a grading scheme, GAMBIT by default will not apply the same grading distribution on the opposite edge during MAP meshing. When appropriate, this situation can be avoided by changing the default value of MESH Æ MAP Æ MATCH_PREMESHED_EDGE_GRADING from 0 to 1.
b. MESH Æ FACE, EXACT_MESH_EVALS change to 1
6. Face Meshing with Tri Scheme
The maximum number of tri elements on a single face is limited to 500000. This limit can be adjusted by resetting the value of MAX_FACES under MESH Æ TRIMESH.
Introduction
GAMBIT provides many important tools for geometry creation and meshing. In most of the cases, you do not have to change the defaults. However, optimal creation of certain geometries and meshes may require modifications to the default settings.
Frequently Modified Defaults in GAMBIT
Purpose: This document contains a list of defaults in GAMBIT that may be modified in order to control the behavior of the program such as GUI layout, graphics display, and smoothing characteristics for meshing algorithms. Situations where these changes in defaults may be helpful are discussed, with examples.
9. Node Placements after Meshing a Face
An exact projection from facets to a real surface can lead to distorted and highly skewed meshes for complex/curved geometries. The default value for MESH Æ FACE Æ PROJECT_TO_SURFACE can be changed from 1 to 0 to suppress exact projection.
PYRAMID_INSERT_TET
PYRAMID_OFFSET_METHOD
8. Size Function Background Grid
In many cases, when sizing functions are used while meshing, the background grid is not resolved properly or is under-resolved.
3. Splitting Virtual Geometries
Splitting of virtual geometries is not enabled by default. To split virtual geometry with a real or virtual entity, change the default value of VIRTUAL_FACE_FACE_SPLIT from 0 to 1 under GEOMETRY Æ FACE.
To improve mesh quality, increase the value of TOOLSÆ SFUNCTION Æ BGRID_MAX_TREE_DEPTH from default value of 16 to an acceptable value that will help in obtaining a better quality mesh. A value of –1 puts no limits on the background tree depth, but makes Size Functions slow for larger models. The above figures show the background grid with BGRID_MAX_TREE_DEPTH value of 16 and 19 respectively.
2. Undo Levels
The default number of UNDO levels is 10, but can be increased or reduced by modifying the value of the default for LEVEL under GLOBAL Æ UNDO category. A lower value may be necessary for large models to reduce the memory ity
The default scheme used for examining the mesh is equisize skewness, which is accessible through Mesh Æ Volume Æ Check Volume Meshes. The default scheme can be changed by modifying the value of ELEMENT_3D_QUALITY default under MESH Æ EXAMINE. The corresponding default for 2D is ELEMENT_2D_QUALITY. The available methods are listed against the corresponding variable.
Product Version: GAMBIT 2.3 and onward Authors: Shariq M. Khan and Ajay Parihar
5. Face Meshing with Map Scheme
While generating a mapped mesh on small scale geometries (of the order of 1e-5 or lower), GAMBIT may generate distorted or irregular cells at the face corners. This problem can be rectified by modifying either one of the following defaults:
PYRAMID_OFFSET_DISTANCE
Significance
Defines the height of pyramids and thereby affects their quality. Try values similar to the size of the quad cells if the default fails. Controls insertion of a tetrahedral cell between two pyramids during initialization. The default option is Off. If initialization fails, turn this option On. Skewness-based default method for growing pyramids. Use the neighbor method if the default fails.
Smoothing Option in Cooper Tool
If the area/shape of source faces is significantly different, the Cooper scheme may generate highly skewed elements. In such situations, it is recommended to disable the SMOOTH_PROJECTED_FACE_MESH option under MESH Æ COOPER by resetting the value to 0
7. Pyramid-Related Options for Tetrahedral Meshing
GAMBIT will grow a transition layer of pyramids while generating tetrahedral elements on a three-
dimensional geometry with quadrilateral elements on the faces. This operation may fail in situations where the quad elements have large aspect ratio. A remedy is to change the following defaults in the MESH Æ TETMESH section. Parameter
11. Exporting 2D Mesh
If the mesh lies in a plane parallel to the XY plane within a specified tolerance value (default is 0.0001), the 2D mesh can be exported from GAMBIT. To export the 2D mesh, the maximum and minimum zcoordinate of the nodes should be less than the default value. The default tolerance value can be changed using the FILE_IO.MESH.EXPORT_2D_TOLERANCE option.
1. Background of Graphics
The default background color in GAMBIT is black. You can modify it by specifying the required color in WINDOWS_BACKGROUND_COLOR default under GRAPHICS Æ GENERAL.
4. Edge Meshing on a Mapped Face
Use of the MAP meshing scheme on a face requires the same node count on the opposite edges. If one of the edges is premeshed with a grading scheme, GAMBIT by default will not apply the same grading distribution on the opposite edge during MAP meshing. When appropriate, this situation can be avoided by changing the default value of MESH Æ MAP Æ MATCH_PREMESHED_EDGE_GRADING from 0 to 1.