This page is currently under development. Content may be incomplete or contain inaccuracies. If you notice any errors or have suggestions, please contact us.
Simulation & Modeling Data Types & File Formats
Simulation and modeling workflows produce a variety of data types — from mesh definitions and solver input files to large time-dependent result datasets and post-processing outputs. This page covers the most important formats.
Mesh and Geometry Formats
STL (Stereolithography, .stl)
A simple surface mesh format using triangulated surfaces. Does not support volume elements or metadata.
- Use: 3D printing, CAD-to-simulation geometry transfer, surface visualization
- Tools: Gmsh, ParaView, MeshLab, FreeCAD
- Note: Available in ASCII and binary variants; binary is much more compact
STEP (.step, .stp)
Standard for the Exchange of Product Model Data — an ISO standard for CAD geometry exchange.
- Use: CAD geometry exchange between software, simulation preprocessing
- Tools: FreeCAD, SALOME, CATIA, SolidWorks
- Spec: ISO 10303
MSH (.msh)
Gmsh's native mesh format supporting 1D, 2D, and 3D elements with physical groups and tags.
- Use: Mesh generation for FEA/CFD solvers
- Tools: Gmsh, FEniCS, GetDP
- Spec: Gmsh File Formats
CGNS (.cgns)
CFD General Notation System — a standard for CFD data including grids, flow solutions, and boundary conditions.
- Use: CFD mesh and solution exchange between solvers
- Tools: ANSYS, OpenFOAM (with converters), ParaView
- Spec: CGNS Project
EXODUS II (.exo)
A finite element data format built on NetCDF/HDF5, supporting unstructured meshes with time-dependent variables.
- Use: FEA results, multi-physics simulations
- Tools: ParaView, Cubit, SEACAS
- Spec: Sandia SEACAS
Solver Input and Output Formats
OpenFOAM Case Directory
A directory-based structure containing mesh (polyMesh/), initial/boundary conditions (0/), solver settings (system/), and time-step results. Uses ASCII dictionaries.
- Use: CFD simulations with OpenFOAM
- Tools: OpenFOAM, ParaView, pyFoam
- Spec: OpenFOAM User Guide
Abaqus Input File (.inp)
A keyword-driven text file defining geometry, materials, boundary conditions, and analysis steps for the Abaqus FEA solver.
- Use: Structural, thermal, and multiphysics FEA
- Tools: Abaqus/CAE, CalculiX (partially compatible)
ANSYS Result Files (.rst, .rth)
Binary result files from ANSYS Mechanical containing nodal/element solutions, reactions, and derived quantities.
- Use: Post-processing ANSYS simulations
- Tools: ANSYS Mechanical APDL, pyansys (Python)
Result and Visualization Formats
VTK / VTU (.vtk, .vtu, .vtp, .vts)
Visualization Toolkit formats for structured and unstructured mesh data with associated field variables. VTU (unstructured) is the most commonly used variant.
- Use: Simulation result visualization, data exchange between tools
- Tools: ParaView, VTK (Python), Mayavi, PyVista
- Spec: VTK File Formats
HDF5 (.h5, .hdf5)
Hierarchical Data Format version 5 — a flexible binary format for large, structured datasets with built-in compression and parallel I/O support.
- Use: Large simulation outputs, restart files, parameter studies
- Tools: h5py (Python), HDFView, ParaView
- Spec: HDF Group
EnSight Gold (.case + .geo + .scl/.vec)
A multi-file format for transient simulation results, widely supported by commercial and open-source tools.
- Use: CFD and FEA transient results
- Tools: ParaView, EnSight, ANSYS
CSV / TSV (.csv, .tsv)
Plain-text tabular data for extracted quantities like time histories, convergence data, or probe measurements.
- Use: Monitoring data, post-processed scalar quantities, comparison with experiments
- Tools: Any spreadsheet or programming language
Workflow and Provenance Formats
YAML / JSON (.yaml, .json)
Human-readable configuration formats used for simulation parameters, workflow definitions, and metadata.
- Use: Solver configuration, parameter studies, workflow pipelines
- Tools: Any text editor, Python (PyYAML, json)
Provenance Metadata (W3C PROV)
A set of standards for recording the provenance of data and processes, important for reproducibility.
- Use: Tracking simulation lineage and parameter history
- Spec: W3C PROV
Format Selection Guide
| Use Case | Recommended Format |
|---|---|
| CAD geometry exchange | STEP |
| Mesh generation | MSH (Gmsh) |
| CFD meshes and solutions | CGNS or OpenFOAM native |
| FEA results | VTU or EXODUS II |
| Large time-series data | HDF5 |
| Visualization | VTK/VTU |
| Configuration files | YAML |
| Extracted scalar data | CSV |