OpenFOAM Variants: A Comprehensive Summary
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OpenFOAM (Open Field Operation And Manipulation) is a widely-used open source computational fluid dynamics (CFD) software that has evolved into several distinct variants over its development history. There are indeed three main branches of OpenFOAM, each with different focuses and development philosophies.
The Three Main OpenFOAM Variants
1. OpenFOAM Foundation
Developer: The OpenFOAM Foundation, with development by CFD Direct Current Version: OpenFOAM v13 (released July 2025) Release Schedule: Annual releases Website: openfoam.org
The OpenFOAM Foundation distributes OpenFOAM exclusively as free and open source software under the General Public License (GPL) v3. This version is developed by CFD Direct and released through The OpenFOAM Foundation, a not-for-profit organization.
Key Features:
- Ownership: The Foundation owns the copyright of the code it distributes
- Development Focus: Emphasizes robustness, usability, and extensibility
- Numbering System: Uses sequential numbering (v1, v2, v3… v13)
- Academic Preference: More commonly used in academia
- Recent Improvements: Version 13 includes rewritten mesh zones, field-based Lagrangian improvements, enhanced MULES algorithm, and better visualization support
2. ESI-OpenCFD
Developer: OpenCFD Ltd (wholly owned subsidiary of ESI Group, now part of Keysight Technologies) Current Version: OpenFOAM v2506 (released June 2025) Release Schedule: Bi-annual releases (June and December) Website: openfoam.com
This version is maintained by ESI-OpenCFD and has been the commercial fork since 2016. OpenCFD Ltd owns the OpenFOAM trademark.
Key Features:
- Trademark Owner: OpenCFD Ltd owns the registered OpenFOAM trademark
- Numbering System: Uses year-month format (v2506 = June 2025)
- Industry Focus: More commonly used in industry
- Advanced Features: Includes overset meshing capabilities not available in the Foundation version
- Frequent Updates: Releases every six months with extensive quality assurance testing
- Professional Support: Backed by Keysight’s worldwide infrastructure and support services
3. foam-extend
Developer: Community-backed fork maintained by Wikki Ltd Current Version: foam-extend 5.0 Website: foam-extend project on SourceForge
foam-extend is a community-driven fork that diverged from the main OpenFOAM development line, focusing on preserving and extending advanced features.
Key Features:
- Community-Driven: Open project welcoming contributions from all users and developers
- Extended Functionality: Contains features that were removed from other OpenFOAM versions
- Specialized Applications: Strong focus on fluid-structure interaction, turbomachinery, and advanced CFD features
- Different Architecture: Uses different naming conventions and setup procedures compared to other versions
- Advanced Features: Includes general grid interpolation (GGI), block-coupled matrix support, comprehensive dynamic mesh capability, and finite area methods
Historical Development
The complex history of OpenFOAM development explains the current fragmentation:
- 1989: Henry Weller creates “FOAM” at Imperial College London
- 2004: OpenFOAM released as open source by OpenCFD Ltd
- 2011: OpenCFD acquired by SGI; OpenFOAM Foundation created to hold copyright
- 2012: OpenCFD acquired by ESI Group
- 2014: Henry Weller and Chris Greenshields leave ESI to form CFD Direct
- 2016: OpenCFD begins releasing its own version directly (v1606+)
- 2024: ESI OpenCFD becomes part of Keysight Technologies
Key Differences Summary
| Aspect | OpenFOAM Foundation | ESI-OpenCFD | foam-extend |
|---|---|---|---|
| Release Frequency | Annual | Bi-annual | Irregular |
| Numbering | Sequential (v13) | Year-Month (v2506) | Version numbers (5.0) |
| Primary Users | Academia | Industry | Specialized research |
| Key Features | Robustness, usability | Overset meshes, commercial support | Advanced CFD features, FSI |
| License | GPL v3 | GPL v3 | GPL v3 |
| Support | Community, CFD Direct training | Professional support | Community |
Which Version to Choose?
The choice depends on your specific needs:
- Students and General Learning: Any version works well, but Foundation version may be preferable for academic use
- Advanced Features: Check specific capabilities - ESI version for overset meshes, foam-extend for fluid-structure interaction
- Industry Applications: ESI version often preferred for commercial applications
- Research: Consider foam-extend if you need specialized advanced features that were removed from other versions
All three versions maintain compatibility with standard OpenFOAM solvers and cases, though some differences exist in advanced features and specific implementations.
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