About OpenFOAM
OpenFOAM (for "Open-source Field Operation And Manipulation") is a C++ toolbox for the development of customized numerical solvers, and pre-/post-processing utilities for the solution of continuum mechanics problems, including computational fluid dynamics (CFD) . It has an extensive range of features to solve anything from complex fluid flows involving chemical reactions, turbulence and heat transfer, to solid dynamics and electromagnetics.
Learn more about OpenFOAM at https://openfoam.org or https://openfoam.com.
There is a number of different flavours of OpenFOAM that are all based on the original FOAM-code. To navigate the different versions, the unofficial OpenFOAM wiki may help you out. The tutorials and installations linked at this site will focus on the versions available from OpenFOAM Foundation and ESI-OpenFOAM.
How to download and install OpenFOAM
OpenFOAM is available from the OpenFOAM Foundation or ESI-OpenFOAM which licenses it free and open source under the General Public Licence. As mentioned above, OpenFOAM is mainly developed and distributed for Linux, but NTNU HCP GROUP has made some very good, detailed instructions on how to install OpenFOAM if you have Windows or macOS (previously Mac OS X and later OS X) as well. Their installation guides are listed below: