OpenFOAM

OpenFOAM is an open source software suite written in C++, designed primarily around three-dimensional continuum mechanics, although its capabilities extend beyond this. The library headers for OpenFOAM use their own syntax and operators to build a framework for fully-realized vector field mathematics in three-dimensional Cartesian coordinates. Tensors are also fully supported in these operations, although tensor calculus is not included.

1 What's FOAM got to do with it?

In this world, many acronyms cleverly spell what they are about. Make no mistake, OpenFOAM is not one of those acronyms. Indeed several oddly chosen acronyms can be found within OpenFOAM's reach. For instance, the combined PISO and SIMPLE solver is has the unfortunate name "pimpleFoam". FOAM itself stands for Field Operation and Manipulation, referring to the mathematical nature of the code, not bubbly frothiness. So it really has nothing to do with foam... unless, of course, you are using it to model foam. Perhaps the developers were more concerned about what went into the code, rather than what to call it.

2 Origins

OpenFOAM, originally called FOAM, was proprietary software developed by Nabla Ltd., somehow associated with TFD Chalmers University, in Sweden. In 2004 Nabla Ltd. ceased operation and released FOAM as open source under GNU General Public License, under the name "OpenFOAM". At this point two independent companies were created:

• OpenCFD Ltd. (maintains official OpenFOAM); and
• Wikki Ltd. (maintains foam-extend).

Both of these companies were started by some of FOAM's original developers and have nothing to do with one another. Each company maintains their own variation of OpenFOAM.

3 OpenFOAM forks and variations

Although there are several forks and variations to OpenFOAM, the two main lines of development (referred here as variations) are those maintained by each company and that are described in more detail in the following subsections:

• Official OpenFOAM is maintained by OpenCFD Ltd.
• foam-extend is maintained by Wikki Ltd.

Note: For a more complete list of all existing forks and variants, please refer to the page Forks and Variants.

3.1 Official OpenFOAM

The official OpenFOAM project is maintained by:

• OpenCFD Ltd., which is the trade mark holder of "OPENFOAM";
• OpenFOAM Foundation, the copyright holder.

This variation is likely the most installed. Some features are available in this variation that are not available in the foam-extend variation. However, foam-extend gradually incorporates these changes into its source code, albeit one or two years later. At present, features that only appear in the official OpenFOAM include (note: the following list is likely outdated):

• runtime selectable turbulence wall functions - alternate wall functions can be used without rewriting the turbulence models;
• density-based thermophysical model - allows for the full energy equation with liquids; and
• Boussinesq buoyancy SIMPLE solver.

For the full list, please read the release notes for each major version of each variation, which is provided on this wiki's Main Page.

3.2 foam-extend

The foam-extend project is maintained by Wikki Ltd.. The nomenclature of each version has changed overtime and for an historic record, it's as follows:

• OpenFOAM 1.4-dev [1]
• OpenFOAM 1.4.1-dev [2]
• OpenFOAM 1.5-dev [3]
• OpenFOAM 1.6-ext [4]
• foam-extend 3.0, 3.1 and onwards [5]

Notes

Usually dev refers to a developmental version which will eventually become part of the release. In foam-extend, this was not the case: 'dev' is the name of the core component of the foam-extend project.

The ext suffix came as an intermediate renaming of the dev to the extend profile of development.

Complete renaming to foam-extend occurred with the release of foam-extend 3.0: Release Notes for foam-extend 3.0

This project is open to community contributions (see Extend-bazaar), none of which get adapted into the official OpenFOAM. Therefore foam-extend has a vast library of capabilities unmatched by the official OpenFOAM project, including (note: this list needs to be revised):

• GGI interfaces - useful for rotating reference frames, and stitching together multiple meshes;
• groovyBC - allows arbitrary boundary conditions to be specified, without requiring coding / compiling;
• newer rectangular matrix solvers' and
• pyFOAM - a front end that makes managing OpenFOAM cases easier, i.e. it makes available many features that users of other software suites take for granted, such as:
  • easily changing the case setup; and
  • plotting the residuals on a graph as the solver is running.

For the full list, please read the release notes for each major version of each variation, which is provided on this wiki's Main Page.

Many of the contributions are compatible with both variations of OpenFOAM, and can be manually installed as desired.

The official OpenFOAM and foam-extend are two different open source projects. The only reason they have not completely diverged is because foam-extend continues to adapt the new releases of official OpenFOAM into its own code. Therefore, new features appearing in official OpenFOAM eventually become part of foam-extend. These adaptations can take one or two years. This practice continues.