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CUBIT Toolkit

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CUBIT 15.1 Release Notes

CUBIT 15.1 Logo
 

Product Description

New Features CUBIT 15.1

CUBIT 15.1 Documentation

Product Highlights

Limitations CUBIT 15.1

CUBIT 15.1 Contents of Release

Contact Information

Defects Fixed CUBIT 15.1

Platforms Supported

 

Known Defects CUBIT 15.1



 

Product Description

CUBIT is a full-featured software toolkit for robust generation of two- and three-dimensional finite element meshes (grids) and geometry preparation. Its main goal is to reduce the time to generate meshes, particularly large hex meshes of complicated, interlocking assemblies.

 

Product Highlights

Meshing: CUBIT is a solid-modeler based preprocessor that meshes volumes and surfaces for finite element analysis. Mesh generation algorithms include quadrilateral and triangular paving, 2D and 3D mapping, hex sweeping and multi-sweeping, tet meshing, and various special purpose primitives. CUBIT contains many algorithms for controlling and automating much of the meshing process, such as automatic scheme selection, interval matching, sweep grouping and sweep verification, and also includes state-of-the-art smoothing algorithms.


Geometry Preparation: One of CUBIT's strengths is its ability to import and mesh geometry from a variety of CAD packages. CUBIT currently integrates the ACIS and Catia geometry kernels directly within its code base, allowing direct manipulation of the native CAD geometry format within CUBIT. This reduces the errors and anomalies so often associated with geometry translation. CGM (Common Geometry Module) also boasts a facet-based geometry kernel developed at Sandia that can be used for remeshing or editing old mesh files or models defined by triangle facets. In addition, CUBIT has developed a comprehensive virtual geometry capability that permits local composites and partitions to geometry without modifying the underlying native geometry representation. The user can choose to ignore, clean-up or add features to the model allowing greater flexibility to meshing algorithms to generate better quality elements.


CUBIT Environment: CUBIT has developed both a convenient command line interface with an extensive command language as well as a polished graphical user interface environment. The GUI is based upon the cross-platform standard QT, which allows the same look and feel on all supported platforms. Also included is a graphical environment based upon the VTK graphics standard which has been optimized for display and manipulation of finite element data and geometry. Fast, interactive manipulation of the model is a tremendous advantage for models with thousands of parts or millions of elements.


For more information on CUBIT, including licensing arrangements and terms see the CUBIT website http://cubit.sandia.gov

 

New Features in CUBIT 15.1

Index of New Features

 

Significant Command Syntax Changes

 

Group Command Changes

 

Meshing

 

Sculpt Enhancements

Improved Triangle and Tet Meshing

Hexahedral Mesh Scaling

Export m2g

Hex Cleanup

Improved ExodusII sizing field support

Sphere Meshing Scheme

 

Geometry

 

ACIS R25 SP1 Upgrade

 

Import/Export

 

NetCDF4/HDF5 support for Exodus files

'water_tight' option added to export STL command

Exporting free mesh triangles to an STL file

Improved block, sideset and nodeset commands when adding and removing entities

Fluent binary import support

 

Graphics, Utilities, etc.

 

Improved Graphics Performance

Improved Entity Specification For Group Commands

Added "Common_To" Extended Parsing Keyword

Improved Metadata Removal

 



Significant Syntax Changes


Group Command Changes

The Group command has been changed significantly in CUBIT 15.1. Journal files from earlier versions need to be updated to give the same behavior in 15.1 as in the earlier version. This change was deemed necessary in order to make the group commands consistent with other commands in CUBIT in the use of names and other aspects of Extended Parsing as described in the documentation.


Probably the biggest change is in using names to add geometry entities when creating a group. In CUBIT 15.0 and earlier versions, the name string is treated as a substring, and all entities with names that contain the substring are added to the group. Starting in CUBIT 15.1, the string is treated as a regular expression, so wildcard characters (*) must be added to achieve the previous substring behavior. Without wildcards, an entity's name must match the string exactly for the entity to be added to the group. The keyword with is also now required before the name keyword.


Old syntax:

group 'rivet_line_g' add volume name "rivet_line"

New equivalent syntax:

group 'rivet_line_g' add volume with name "*rivet_line*"


Below are additional examples of the old syntax with the new required syntax to achieve the previous behavior:


Old syntax:

group 'first' surface merged

New equivalent syntax:

group 'first' add surface is_merged


Old syntax:

group 'first' surface unmerged

New equivalent syntax:

group 'first' add surface not is_merged


Old syntax:

group 'first' surface meshed

New equivalent syntax:

group 'first' add surface is_meshed


Old syntax:

group 'first' surface unmeshed

New equivalent syntax:

group 'first' add surface not is_meshed


Old syntax:

group "my_maps" add surface with scheme "map"

New equivalent syntax:

group "my_maps" add surface with has_scheme "map"


Here is an example of the improved functionality with Extended Parsing. In previous versions the following command created an empty group. Now volume 1 and the surface named 'mysurf' are both added to the group, making the behavior consistent with other CUBIT commands. Note that in this case, 'mysurf' is not treated as a substring, so only one surface named 'mysurf' is added to the group.


group 'mygroup' add volume 1 surface with name 'mysurf'




Meshing


Sculpt Enhancements


Sculpt is a new parallel hex meshing method that was first released in version 15.0. In this release we have incorporated many new enhancements and bug fixes that will make the method more robust and usable. The following is a summary of the enhancements for version 15.1.


1. Improved Smoothing: The automatic smoothing procedures in Sculpt have been enhanced, resulting in dramatic improvements in the success rate and quality of meshes generated with Sculpt. A new automatic spot-smoothing algorithm that focuses only on the poorest quality elements is now employed. The user can also control the target minimum quality criteria and the number of smoothing iterations. Shown below is a histogram comparing the minimum element Scaled Jacobian (SJ) on a test suite of 50 CAD models meshed with Sculpt in version 15.0 (Before) and version 15.1 (After).

Sculpt mesh quality comparison


2. Input File: Sculpt can be run directly from CUBIT or from the operating system (OS) command line. To simplify running Sculpt from the OS, a new input file format is now available where a text file may be used to define arguments and parameters in a more user-friendly and readable format. The OS command to run sculpt using an input file is sculpt -i filename.i. The following is a simple example of a sculpt input file:

Sculpt Input File


3. Command Line Help: When running Sculpt from the OS command line, detailed documentation on each of the Sculpt command arguments can be printed to the window using the -h option. As an example, the image below illustrates the output from the OS command sculpt -h input_file. To get a summary of all commands, typing sculpt with no arguments will show a complete list.

Sculpt command line help


4. Microstructures: A series of new options and features have been added to support all-hexahedral mesh generation for Microstructures. Rather than using a geometric representation (STL file), a microstructures input file contains only volume fraction data for each cell of a Cartesian grid representing the different grain structures. The image below shows a mesh and the resulting geometry created from a microstructures file using Sculpt.

Sculpt microstructures

Three new options for importing Microstructures data into Sculpt are now available. Each of these formats defines a Cartesian grid where material data is provided at each cell. Sculpt will generate a hex mesh with one block per material with smooth conforming interfaces between materials. Automatic nodesets are defined at domain boundaries and at material triple junctions. The -j option may be used to run on multiple processors as well as the --pillow option to improve quality at material interfaces. The new import format options include:

--input_micro: Import an ascii text file containing volume fraction data for each cell of a Cartesian grid.

--input_cart_exo: Import an Exodus file containing a Cartesian grid of cells grouped by material.

--input_spn: Import an ascii text file containing one integer per cell of a Cartesian grid, where each integer represents a unique material identifier.

Although most options are set to default values, the user may control the resulting mesh with some of the following new features:

--smooth 9: Surface smoothing without projecting. This option is effective in smoothing out noisy surface data common in microstructures. This is now the default for Microstructures file formats.

--csmooth: Curve smoothing options are now available. Microstructures formats will use a new Hermite interpolation algorithm (csmooth=2) resulting in smoother curve definitions defining triple junctions.

--micro_expand: Expands the global Cartesian domain by a specified number of layers. This option is effective in improving mesh quality at boundaries where interfaces meet the boundary at small angles.

--pillow 3: A new option for pillowing where a layer of hexes is inserted at each of the six faces of the global Cartesian domain. This is sometimes useful in improving mesh quality near the domain boundaries.


5. Stair-step Option: A new "fast" option for generating a stair-step mesh is now available. Stair-step meshes are composed entirely of cubes from the base mesh, with the boundaries left unsmoothed. The new "fast" option will ignore non-manifold conditions between adjacent elements to reduce meshing time. To use this feature, add the option -str 3 to the command line, or stair = 3 in the input file. The images below show a model meshed with two different base mesh sizes using the fast stair option.

Sculpt fast stair step


Improved Triangle and Tet Meshing


The tetrahedral meshing in CUBIT relies on an industry-standard third party library developed and distributed by Distene S.A.S. CUBIT 15.1 features new triangle meshing algorithms from MeshGems-CADSurf which is also developed and distributed by Distene. Since all tet meshing procedures require an initial triangle mesh, more tightly coupled tet and triangle meshing algorithms result in an overall improved mesh with better default mesh sizing and quality.


CUBIT's default behavior will now utilize the MeshGems triangle meshing algorithm to mesh surfaces either alone or as part of tet meshing. This behavior is built into CUBIT's existing tetmesh and trimesh schemes. The triadvance and tridelaunay schemes continue to be maintained and can be specified instead of the default trimesh scheme.


One of the main benefits of the new default tet meshing procedure is the ability to automatically adapt element sizes based on geometric features such as curvature and narrow regions. User settings allow for changing the sensitivity of the adaptive mesh to better approximate the underlying geometry. The following figures illustrate the differences between a default tet mesh generated in CUBIT 15.0 and CUBIT 15.1.


MeshGems

MeshGems


Hexahedral Mesh Scaling


The Scale Mesh command has been significantly improved. Originally released in CUBIT 15.0, the command syntax is now:

Scale Mesh [Multiplier <value>] [minimum <value>] [{SWEPT_BLOCKS|structured_blocks}] [feature_angle <value>] [force_structured in {[volume <ids>] [surface <ids>]}]


The Scale Mesh command globally refines or coarsens the current hexahedral mesh in CUBIT based upon the input Multiplier. For example, if a multiplier of 2.0 is specified, the scale mesh command attempts to double the number of hexahedral elements in the mesh, with the new elements spread evenly across the entire model, effecting global refinement. Similarly, if a multiplier of 0.75 is specified, the scale mesh command attempts to reduce the number of hexahedral elements in the mesh by 25%, spread evenly across the model.

New for CUBIT 15.1 are the arguments swept_blocks, structured_blocks, feature_angle, and force_structured. These new arguments provide user controls to ensure a more evenly distributed refinement/coarsening across model. In CUBIT 15.1, mesh scaling is no longer required to honor every mesh singularity in favor of a more evenly distributed refinement. Specify structured_blocks if you desire the 15.0 behavior of honoring every mesh singularity. The 15.1 default, swept_blocks, will provide a smoother refined mesh as illustrated in the images below.



Title



Export m2g


A new command for exporting an exodus mesh file along with its geometry association has been added to CUBIT. The command syntax is:


Export m2g "<fileroot>" [block <ids>] [overwrite]


This command writes three files to disk.


  • <fileroot>.exo : an exodus file containing the mesh in the specified blocks.
  • <fileroot>.sat : an ACIS file containing the geometry in the model.
  • <fileroot>.m2g : a mesh-to-geometry association file that describes which mesh entities are associated to each geometry entity.


The mesh-to-geometry association file can be imported into the Sierra STK mesh_scale program, which is a batch version of the new hexahedral mesh scaling command described above. We anticipate that this command will become part of other meshing processes which are launched from CUBIT.



Hex Cleanup


A new hex cleanup capability has been added in CUBIT 15.1 to improve mesh quality when the mesh contains columns of "high-angle" hexes on volume boundaries. A combination of column operations is done to add three additional columns of hexes to mitigate the high angle. The command is:


Cleanup Volume <id_range> [angle <value=150>]


Boundary hexes with adjacent faces having a dihedral angle greater than the specified angle (default is 150 degrees) will be cleaned up.


Example of hexahedral mesh with case handled by hex mesh cleanup.



After hex mesh cleanup.





Improved ExodusII sizing field support


Support for ExodusII sizing fields has been improved. Surface and Curve meshing will default to using a 3d sizing field, and curve meshing will now default to using a 2d sizing field. There have also been several robustness improvements.



Sphere Meshing Scheme


The sphere meshing scheme for volumes has been improved, including:

  • smarter biasing of element size by default
  • mesh symmetry is maintained by default
  • volume interval sizes are applied to elements near the center rather than at the surface
  • an improved sphere meshing algorithm with smoother size transitions and improved element quality

The sphere scheme command panel has also been improved to include a new on/off toggle for smoothing, and the default parameters for advanced options are automatically displayed and updated in the command panel based on current interval size.


The image below shows a sphere scheme mesh in version 15.1 with default settings using the smooth option. Note the improved regularity and symmetry of the mesh.


Sphere scheme




Geometry


ACIS R25 SP1 Upgrade


CUBIT 15.1 includes an update to the ACIS solid modeling libraries to version R25 SP1. The new version contains various improvements and bug fixes. As with any upgrade to the ACIS solid modeling libraries, there is the potential for geometry id changes in CUBIT compared to earlier versions. See IDless journal files in the CUBIT User Manual for information on updating old journal files to work with the latest CUBIT version.




Import/Export



NetCDF4/HDF5 support for Exodus files


The EXODUS II export capability has been enhanced to allow the option of exporting in the NetCDF4/HDF5 format. This format supports larger files and unlimited dimension. The file export dialogs support this option, or alternatively it may be enabled/disabled with the command:


Set Exodus NetCDF4 [on|OFF]


'water_tight' option added to export STL command


The water tight option guarantees that for solid volumes a water-tight set of facets is exported to the STL file.


Export STL [ASCII|binary] 'filename' [<entity_list>] [tri <id_range>] [angle=15] [mesh|water tight] [Overwrite]


Sometimes exported facets on adjacent surface do not line up.



Using the water tight option ensures the facets will line up.




Exporting free mesh triangles to an STL file


The export STL capability has been expanded to allow free mesh triangles to be exported. The new command syntax is:


Export STL [ASCII|binary] 'filename' [<entity_list>] [tri <id_range>] [angle=15] [mesh|water tight] [Overwrite]


Improved block, sideset and nodeset commands when adding and removing entities


The block, sideset and nodeset commands have been improved to make them more consistent with the group command when adding and removing entities. The add and remove keywords can be specified after the block, sideset, or nodeset id, respectively. For example, the following commands:


block 1 add volume 1

block 1 remove hex 1


create block 1 containing all of the elements in volume 1 except for hex 1.


Fluent binary import support


The Fluent import capability has been enhanced to support binary .msh files.





Graphics, Utilities, etc.


Improved Graphics Performance


CUBIT graphics has been improved for faster reponse times with larger models. Interactive graphics manipulations are generally improved. For instance, a certain model with 1000 volumes has an interaction time is about 2.7 times faster. CUBIT has also been enhanced to use multiple threads while generating a graphical representation of the geometry model. This is usually noticeable when opening or importing large models.


Improved Entity Specification For Group Commands


The entity specification for group commands has been changed to be consistent with the rest of CUBIT. The most common change users will experience is that the "with" keyword is now required when using entity names. For example:


group 1 add volume with name "top"


See Extended Entity Specification for additional information.


Added "Common_To" Extended Parsing Keyword


The "common_to" keyword has been added to CUBIT's extended parsing capabilities. It uses the following format:


{Entity_Type} common_to {Entity_List}


Similar to the "in" keyword, "common_to" uses topological traversal to find entities of the indicated type in the provided entity list. However, whereas the "in" keyword directs CUBIT to retain all entities of the indicated type, "common_to" retains only those that are shared by the provided entity list. For example the command:


group 'mygroup' add curve common_to volume 1 2 3


directs CUBIT to find all of the curves that are shared by volumes 1 2 and 3 and adds them to the group named 'mygroup'.


Improved Metadata Removal


A new propagate option has been added to the metadata remove command for assemblies. When this option is included, children of the given assembly (parts or sub-assembies) will also be removed. This eliminates the previous restriction that the user must manually remove all children of an assembly before removing the assembly itself. This option is only valid for removing assembly metadata:


metadata remove assembly "AssemblyPath" [instance <id>] [propagate]


Limitations in CUBIT 15.1


No known limitations.  


Fixed Defects in CUBIT 15.1


The following items are the user-reported bugs deemed "critical" or "blocker" fixed since the last release of CUBIT. For more information contact Cubit Help (cubit-help@sandia.gov).


Ref #

Resolved Defect*

10677 skeleton sizing is broken when pre-existing mesh exists
10679 Sizing sources documentation is missing
10719 3D Map Mesher produces bad mesh

10721

Meshing crash due to bad sweep command sent to CUBIT

11015 CUBIT 15.0 aprepro loops crashing
11105 QT Loft Command Panel becomes unuseable with lots of vertices and vertex matching ON
11135 writing large exodus file is excessively slow
11250 Sphere import in fails when importing mesh geom from Exodus

 

 

Known Defects in CUBIT 15.1


No known critical or blocker defects.  


Documentation Updates


The CUBIT 15.1 online documentation may be found here. Both a PDF version and a Microsoft Word version are also available for download. The CUBIT GUI installation also includes the full user documentation included with the program. The user's manual may be accessed from the Help menu.

CUBIT 15.1 Contents of Release


CUBIT Program
: The installation package includes executables and libraries, packaged in tar.gz files for Linux machines. For Windows, the package is in a self-installing executable, and for Mac OS X a .dmg file is provided. Both a command line and GUI version of CUBIT are included with the installation package for all platforms.


Documentation: Linux, Windows and Mac versions include full online documentation.


 

Platforms Supported


CUBIT 15.1 supports the following Platforms:


  • Linux RedHat Enterprise 6, 64-bit

  • Windows 10, Windows 8.1, Windows 8, Windows 7, Vista, 64-bit

  • Mac OS X 10.7 and newer


Non-Sandia Users

CUBIT is freely available for United States government use. For more information on licensing CUBIT, including academic, commercial, and all other use, go to our licensing page. For current CUBIT users, CUBIT 15.1 may be downloaded from the CUBIT download page.

Sandia Personnel Only

Windows
Download a Windows installation file from the CUBIT download page. Double-click the file to install.
MAC OS X
Download a Mac OS X disk image file from the CUBIT download page. Copy the Cubit folder in the disk image to your /Applications or other folder.
LINUX LANS
Check with your local LAN administrator for instructions on how to access CUBIT on your local LAN. In most cases typing one of the following commands at the UNIX prompt should allow you to execute CUBIT.  In some cases, the full path will need to be specified:
/projects/cubit/<cubit_command>

cubit

The latest released 64-bit version (15.1) of CUBIT deployed to the LAN.

cubit -nogui

The latest released 64-bit version (15.1) with just the Command Line and graphics window

cubit -nogui -nographics

The latest released 64-bit version (15.1) with just the Command Line

cubit-15.1

64-bit Version 15.1 with GUI

cubit-beta

The latest beta version still in development

 

Contact Information


CUBIT Help

For general technical questions including download, installation and CUBIT technical assistance.
cubit-help@sandia.gov

CUBIT Licensing and Passwords

Kathy Loeppky
Cubit Licensing
Phone: 505-844-2376
Email: Cub-Req@sandia.gov

CUBIT Support Lead

Cubit Support Lead
Email: cubit-support@sandia.gov

CUBIT Project Lead

Byron Hanks
Sandia National Laboratories
Computational Simulation Infrastructure (org. 1543)
Phone: 505-845-0500
Email: cubit-support@sandia.gov

Web site contact: Cubit Support