Coreform is pleased to announce Coreform Cubit 2023.11, which features many new capabilities and improvements improving support for nuclear energy applications. Enhancements include an exporter to the DAGMC radiation transport code, improvements to the ABAQUS export to support the MCNP radiation transport code, as well as an MCNP importer that reconstructs MCNP models within Coreform Cubit. A new coarse trimesher setting was added to support producing meshes for radiation transport codes used within the nuclear energy industry.
(Download Coreform Cubit here.)
Released: 2 November 2023
Table of Contents
Support for Radiation Transport Codes
Direct Accelerated Geometry Monte Carlo (DAGMC) is a software package that allows users to perform Monte Carlo radiation transport directly on CAD models.
The DAGMC community previously developed a Coreform Cubit plugin. Coreform Cubit now contains native capability to export DAGMC .h5m files. Users familiar with the original DAGMC plugin will now use Coreform Cubit’s native Exodus-based workflows for assigning materials and/or boundary conditions (i.e., block, sideset, nodeset) rather than the group-based workflow implemented within the original plugin.
The Monte Carlo N-Particle® (MCNP®) code, developed by Los Alamos National Laboratory, can be used for general-purpose transport of many particles including neutrons, photons, electrons, ions, and many other elementary particles, up to 1 TeV/nucleon. The transport of these particles is through a three-dimensional representation of materials defined in a constructive solid geometry, bounded by first-, second-, and fourth-degree user-defined surfaces. In addition, external structured and unstructured meshes can be used to define the problem geometry in a hybrid mode by embedding a mesh within a constructive solid geometry cell, providing an alternate path to defining complex geometry.
Coreform Cubit now provides a method for importing MCNP files. The standard MCNP file has a .i extension. This file format contains Constructive Solid Geometry (CSG) models. These models are converted into Boundary Representation (B-Rep) files using the ACIS modeling engine.
Improved assembly support when exporting to ABAQUS / MCNP
Various enhancements made to ABAQUS export include writing additional element sets and node sets based on groups, specifying coordinate frames, and new ‘instance_per_block’ option. These additions will streamline using Coreform Cubit with MCNP.
Write additional element sets and node sets based on groups
Documentation improved for specifying coordinate frames
A new instance_per_block option was added for automatic part instancing based on defined blocks
Coreform Cubit’s previous ability to split fillet surfaces was not ideal, creating a split that looked like a projection of a linear curve. The splitting routine was fixed so that the split follows the curvature of the surface, creating a more expected and ideal result.
The new Reduce Bolt Patch command in Coreform Cubit offers an alternative method for representing bolts in simulations. It replaces bolt geometry with concentric circular surfaces imprinted on the model, centered on the bolt axis. Sidesets are automatically applied to these surfaces, representing preload forces for analysis purposes. By default, the command utilizes the Shigley frustum to determine the radius of the sideset patches, but the desired radii can also be directly designated. Additionally, the resulting patches can be meshed using this command, and sidesets can be customized with incremental IDs and names.
The reduce bolt patch command is one of several options for reducing fastener geometry for use in analysis. This option has also been added to the geometry power tool machine learning tools for classifying geometry. When designated as a bolt, additional solution options are presented that now include the reduce bolt patch command.
A new command panel for setting up and previewing options for the reduce bolt patch comand can be accessed from Geometry->Modify->Volume->Reduce->Bolt Patch
While meshing is most commonly seen as an operation for PDE-based simulations that require high-quality regular-shaped elements for accuracy, there are tangential industry applications that also utilize mesh datastructures in their workflows. Examples of these include additive manufacturing (slice generation) and nuclear energy (Monte Carlo particle transport). These applications typically resolve the geometry to high-accuracy through the use of a minimal number of high aspect-ratio triangles. To support these applications Coreform Cubit now supports a coarse setting in the trimesh scheme. This allows users to visualize the mesh prior to export (e.g., to STL, DAGMC ) as well as produce different density meshes on different geometric entities (as opposed to a global parameter set on export) and otherwise access the full utility of Coreform Cubit when producing their meshes.
Triangle meshing robustness is improved and a correct mesh can now be produced in a few specific combinations of compositing and merging surfaces. Additionally, on some CAD models, triangle meshing would fail due to low precision geometric evaluations. These failures were a regression introduced in a previous version of Coreform Cubit from improving performance. Geometric evaluations were enhanced to retain some performance and re-establish robustness.
Improved robustness of node equivalencing
Equivalencing nodes is now more robust after importing multiple mesh files as free mesh. Additionally, higher order nodes are now equivalenced when they exist. Performance has been improved allowing the equivalence operation to complete quicker on larger models.
Previously, the sculpt command could be executed without arguments, utilizing the current volumes as the default target geometry for meshing. However, to accommodate various file types (e.g., STL, diatom, microstructures) containing geometry, the sculpt command now requires the designation of the target geometry as the first argument when invoking the command.
Coreform Cubit previously performed automatic midnode correction during the import mesh geometry command, enhancing the quality of high-order tetrahedral elements (TET10) by straightening edges when quality was below a designated threshold. Users can now toggle the midnode_correction option during import, allowing control over this capability. By default, midnodes will not be corrected based on quality.
New right-click automatic surface selection options
After selecting two surfaces (or collections of surfaces), a new right-click select between option selects all surfaces between the two already selected surfaces, given there is only a single path of surfaces between them. Merged surfaces are skipped over. If a single surface is selected, the new select enclosure option will select all connected surfaces, forming a water-tight enclosure.
Given a surface, returns all connected, unmerged surfaces.
Determines the effective load radius surrounding a bolt based on the diameter of the head and the upper and lower volume thicknesses based on Shigley.
Cubit bug fixes and enhancements
Improved OpenMPI version compatibility
When running Sculpt on Linux and macOS, the version of OpenMPI used is no longer restricted to version 4.0. One may use any version of OpenMPI which is ABI compatible with version 4.0. This includes 3.0, 3.1, 4.1 and 5.0. Running Sculpt with other versions of OpenMPI may be useful if targeting a specific hardware which the distribution-included OpenMPI doesn’t support.
New extended parsing options with blocks, nodesets and sidesets
Extended parsing of blocks, nodesets and sidesets in mesh is now fully supported. For example, one can get sidesets using a sideset in face 40 syntax or get blocks using a block in hex 32 syntax. This feature now works whether the blocks, sidesets or nodesets are defined by geometry or mesh. This may be useful when writing general commands to work on both types of definitions.
Generalized coordinate frame commands
The syntax for creating coordinate frames has been updated to no longer include the word exodus. The is change is to emphasize that coordinate frames are available for use with ABAQUS as well as EXODUS. Old journal files will continue to work when using the word exodus.
The following locate commands now support an optional string parameter allowing customization of the displayed label. The supplied string is used as the label instead of the default xyz position or name of the entity, as shown below.